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  1. 2
      .github/FUNDING.yml
  2. 26
      .github/workflows/goreleaser.yml
  3. 34
      .github/workflows/test.yml
  4. 108
      .gitignore
  5. 57
      .goreleaser.yml
  6. 674
      LICENSE
  7. 35
      Makefile
  8. 146
      README.md
  9. BIN
      david_dithered.png
  10. 22
      fake_quantizer.go
  11. 10
      go.mod
  12. 28
      go.sum
  13. 290
      main.go
  14. 488
      subcommand_helpers.go
  15. 500
      subcommands.go

2
.github/FUNDING.yml
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github: makeworld-the-better-one
ko_fi: makeworld

26
.github/workflows/goreleaser.yml
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name: goreleaser
on:
push:
tags:
- v*
jobs:
goreleaser:
runs-on: ubuntu-latest
steps:
- name: Checkout
uses: actions/checkout@v2
with:
fetch-depth: 0
- name: Set up Go
uses: actions/setup-go@v2
with:
go-version: 1.16
- name: Run GoReleaser
uses: goreleaser/goreleaser-action@v2
with:
version: 0.x
args: release --rm-dist
env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

34
.github/workflows/test.yml
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name: test
on:
push:
paths-ignore:
- "**.md"
- "LICENSE"
pull_request:
paths-ignore:
- "**.md"
- "LICENSE"
jobs:
test:
runs-on: ubuntu-latest
strategy:
fail-fast: false
matrix:
go-version: ["1.14", "1.15", "1.16"]
steps:
- name: Install Go
uses: actions/setup-go@v2
with:
go-version: ${{ matrix.go-version }}
- name: Checkout code
uses: actions/checkout@v2
- uses: actions/cache@v2
with:
path: ~/go/pkg/mod
key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
restore-keys: |
${{ runner.os }}-go-
- name: Test
run: make

108
.gitignore vendored
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NOTES.md
*.png
*.gif
didder
!david_dithered.png
# Created by https://www.toptal.com/developers/gitignore/api/go,code,linux,windows,macos
# Edit at https://www.toptal.com/developers/gitignore?templates=go,code,linux,windows,macos
### Code ###
.vscode/*
!.vscode/tasks.json
!.vscode/launch.json
*.code-workspace
### Go ###
# Binaries for programs and plugins
*.exe
*.exe~
*.dll
*.so
*.dylib
# Test binary, built with `go test -c`
*.test
# Output of the go coverage tool, specifically when used with LiteIDE
*.out
# Dependency directories (remove the comment below to include it)
# vendor/
### Go Patch ###
/vendor/
/Godeps/
### Linux ###
*~
# temporary files which can be created if a process still has a handle open of a deleted file
.fuse_hidden*
# KDE directory preferences
.directory
# Linux trash folder which might appear on any partition or disk
.Trash-*
# .nfs files are created when an open file is removed but is still being accessed
.nfs*
### macOS ###
# General
.DS_Store
.AppleDouble
.LSOverride
# Icon must end with two \r
Icon
# Thumbnails
._*
# Files that might appear in the root of a volume
.DocumentRevisions-V100
.fseventsd
.Spotlight-V100
.TemporaryItems
.Trashes
.VolumeIcon.icns
.com.apple.timemachine.donotpresent
# Directories potentially created on remote AFP share
.AppleDB
.AppleDesktop
Network Trash Folder
Temporary Items
.apdisk
### Windows ###
# Windows thumbnail cache files
Thumbs.db
Thumbs.db:encryptable
ehthumbs.db
ehthumbs_vista.db
# Dump file
*.stackdump
# Folder config file
[Dd]esktop.ini
# Recycle Bin used on file shares
$RECYCLE.BIN/
# Windows Installer files
*.cab
*.msi
*.msix
*.msm
*.msp
# Windows shortcuts
*.lnk
# End of https://www.toptal.com/developers/gitignore/api/go,code,linux,windows,macos

57
.goreleaser.yml
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project_name: didder
env:
- GO111MODULE=on
before:
hooks:
- go mod download
builds:
- env:
- CGO_ENABLED=0
goos:
- linux
- windows
- darwin
- freebsd
- netbsd
- openbsd
goarch:
- 386
- amd64
- arm64
- arm
goarm:
- 6
- 7
ignore:
- goos: darwin
goarch: 386
- goos: freebsd
goarch: arm
- goos: freebsd
goarch: arm64
- goos: netbsd
goarch: arm
- goos: netbsd
goarch: arm64
- goos: openbsd
goarch: arm
- goos: openbsd
goarch: arm64
archives:
- format: binary
replacements:
darwin: macOS
386: 32-bit
amd64: 64-bit
milestones:
- close: true
changelog:
skip: true

674
LICENSE
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GNU GENERAL PUBLIC LICENSE
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parties who would receive the covered work from you, a discriminatory
patent license (a) in connection with copies of the covered work
conveyed by you (or copies made from those copies), or (b) primarily
for and in connection with specific products or compilations that
contain the covered work, unless you entered into that arrangement,
or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.
12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot convey a
covered work so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you may
not convey it at all. For example, if you agree to terms that obligate you
to collect a royalty for further conveying from those to whom you convey
the Program, the only way you could satisfy both those terms and this
License would be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a single
combined work, and to convey the resulting work. The terms of this
License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License,
section 13, concerning interaction through a network will apply to the
combination as such.
14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions of
the GNU General Public License from time to time. Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.
Each version is given a distinguishing version number. If the
Program specifies that a certain numbered version of the GNU General
Public License "or any later version" applies to it, you have the
option of following the terms and conditions either of that numbered
version or of any later version published by the Free Software
Foundation. If the Program does not specify a version number of the
GNU General Public License, you may choose any version ever published
by the Free Software Foundation.
If the Program specifies that a proxy can decide which future
versions of the GNU General Public License can be used, that proxy's
public statement of acceptance of a version permanently authorizes you
to choose that version for the Program.
Later license versions may give you additional or different
permissions. However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.
15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
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PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".
You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<https://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program
into proprietary programs. If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library. If this is what you want to do, use the GNU Lesser General
Public License instead of this License. But first, please read
<https://www.gnu.org/licenses/why-not-lgpl.html>.

35
Makefile
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GITV != git describe --tags
GITC != git rev-parse --verify HEAD
SRC != find . -type f -name '*.go' ! -name '*_test.go'
TEST != find . -type f -name '*_test.go'
PREFIX ?= /usr/local
VERSION ?= $(GITV)
COMMIT ?= $(GITC)
BUILDER ?= Makefile
GO := go
INSTALL := install
RM := rm
didder: go.mod go.sum $(SRC)
GO111MODULE=on CGO_ENABLED=0 $(GO) build -o $@ -ldflags="-s -w -X main.version=$(VERSION) -X main.commit=$(COMMIT) -X main.builtBy=$(BUILDER)"
.PHONY: clean
clean:
$(RM) -f didder
.PHONY: install
install: dither
$(INSTALL) -d $(PREFIX)/bin/
$(INSTALL) -m 755 didder $(PREFIX)/bin/didder
.PHONY: uninstall
uninstall:
$(RM) -f $(PREFIX)/bin/didder
# Development helpers
.PHONY: fmt
fmt:
$(GO) fmt ./...

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# didder
[![go reportcard](https://goreportcard.com/badge/github.com/makeworld-the-better-one/didder)](https://goreportcard.com/report/github.com/makeworld-the-better-one/didder)
<p align="center">
<img src="david_dithered.png" />
</p>
didder is an extensive, fast, and accurate command-line image dithering tool. It is designed to work well for both power users as well as pipeline scripting.
It is backed by my [dithering library](https://github.com/makeworld-the-better-one/dither), and is unique in its correctness and variety of dithering algorithms. No online or offline tool I know of provides as many options, while being correct (linearizing the image).
## Types of dithering supported
- Random noise (in grayscale and RGB)
- **Ordered Dithering**
- Bayer matrix of any size (as long as dimensions are powers of two)
- Clustered-dot - many different preprogrammed matrices
- Some unusual horizontal or vertical line matrices
- Yours? You can provide your own ordered dithering matrix in JSON format
- **Error diffusion dithering**
- Simple 2D
- Floyd-Steinberg, False Floyd-Steinberg
- Jarvis-Judice-Ninke
- Atkinson
- Stucki
- Burkes
- Sierra/Sierra3, Sierra2, Sierra2-4A/Sierra-Lite
- [Steven Pigeon](https://hbfs.wordpress.com/2013/12/31/dithering/)
- Yours? You can provide your own error diffusion matrix in JSON format
More methods of dithering are being worked on, such as Riemersma, Yuliluoma, and blue noise. If you'd like to help out with development of those methods, or request a new one, please make an issue in my [dither](https://github.com/makeworld-the-better-one/dither) library repo, not this one.
## Features
- Set palette using hex codes, number 0-255 (grayscale), or SVG color names
- Optionally recolor image with a different palette after dithering
- Set dithering strength
- Image is automatically converted to grayscale if palette is grayscale
- Force image to grayscale with `--grayscale`
- Change image saturation, brightness, or contrast before dithering
- Read EXIF rotation tags by default (disabled with `--no-exif-rotation`)
- Downscale image before dithering, keeping aspect ratio
- Upscale image after dithering, without producing artifacts
- Supports input image of types JPEG, GIF (static), PNG, BMP, TIFF
- Output to PNG or GIF
- Process multiple images with one command
- Combine multiple images into an animated GIF
- Uses all CPU cores when possible
## Installation
### Binary
Download a binary from the [releases](https://github.com/makeworld-the-better-one/didder/releases) page. On Unix-based systems you will have to make the file executable with `chmod +x <filename>`. You can rename the file to just `didder` for easy access, and move it to `/usr/local/bin/`.
On Windows you will have to open a terminal or cmd window in the same directory as the EXE file, or [add it to your PATH](https://stackoverflow.com/a/41895179).
Make sure to click "Watch" in the top right, then "Custom" > "Releases" to get notified about new releases!
### From source
**Requirements**
- Go 1.14 or later
- GNU Make
Please note the Makefile does not intend to support Windows, and so there may be issues.
```shell
git clone https://github.com/makeworld-the-better-one/didder
cd didder
# git checkout v1.2.3 # Optionally pin to a specific version instead of the latest commit
make # Might be gmake on macOS
sudo make install # If you want to install the binary for all users
```
## Getting started
```
didder [global options] command [command options] [arguments...]
```
Run `didder` to see some info, and the global options and commands. Run `didder help cmd` or `didder cmd --help` to see information and opions for a specific command.
Each command represents a different dithering algorithm, or set of algorithms.
Here's a fully working command as an example:
```shell
didder --palette 'black white' -i input.jpg -o test.png bayer 16x16
```
This command dithers `input.jpg` to just use black and white (implicitly converting to grayscale first), using a 16x16 Bayer matrix. The result is written to `test.png`.
As another example, here's the command used for the image at the top of the README:
```shell
didder -i david.png -o david_dithered.png --palette 'black white' --recolor 'black F273FF' --upscale 2 bayer 4x4
```
If you'd like the replicate this yourself, the input image is available [here](https://upload.wikimedia.org/wikipedia/commons/7/71/Michelangelo%27s_David_-_63_grijswaarden.png).
## What method should I use?
Generally, using Floyd-Steinberg serpentine dithering will produce results with the fewest artifacts. The command would be:
```shell
didder [palette and I/O options] edm --serpentine FloydSteinberg
```
Playing with the strength of the matrix might also be useful. The example above is at full strength, but sometimes that's too noisy. The command for 80% strength looks like this:
```shell
didder --strength 80% [palette and I/O options] edm --serpentine FloydSteinberg
```
The main reason for using any other dithering algorithm would be
- **Aesthetics** - dithering can be a cool image effect, and different methods will produce different and stronger artifacts
- **Speed** - error diffusion dithering is sequential and therefore single-threaded. But ordered dithering, like using `Bayer`, will use all available CPUs, which is much faster.
If you want to see examples of the different dithering algorithms, you can look at [this directory](https://github.com/makeworld-the-better-one/dither/tree/master/images/output). Or try them out yourself!
## Avoid these mistakes
- It's easy to mess up a dithered image by scaling it manually. It's best to scale the image to the size you want before dithering (externally, or with `--width` and/or `--height`), and then leave it
- If you need to scale it up afterward, use `--upscale`, rather than another tool. This will prevent image artifacts or blurring.
- Be wary of environments where you can't make sure an image will be displayed at 100% size, pixel for pixel. Make sure nearest-neighbor scaling is being used at least.
- Dithered images must only be encoded in a lossless image format. This is why the tool only outputs PNG or GIF.
See [here](https://github.com/makeworld-the-better-one/dither#scaling-images) for more information on these points.
## When to use `--recolor`
The `--recolor` flag exists because when palettes that are severely limited in terms of RGB spread are used, accurately representing the image colors with the desired palette is impossible. Instead of accuracy of color, the new goal is accuracy of luminance, or even just accuracy of contrast. For example, the original Nintendo Game Boy used a solely [green palette](https://en.wikipedia.org/wiki/List_of_video_game_console_palettes#Game_Boy). By setting `--palette` to shades of gray and then `--recolor`ing to the desired shades of green, input images will be converted to grayscale automatically and then dithered in one dimension (gray), rather than trying to dither a color image (three dimensions, RGB) into a one dimensional green palette. This is similar to "hue shifting" or "colorizing" an image in image editing software.
For these situations, `--recolor` should usually be a palette made up of one hue, and `--palette` should be the grayscale version of that palette. The `--palette` could also be just equally spread grayscale values, which would increase the contrast but make the luminance inaccurate.
Recoloring can also be useful for increasing contrast on a strange palette, like: `--palette 'black white' --recolor 'indigo LimeGreen'`. Setting just `--palette 'indigo LimeGreen'` would give bad (low contrast) results because that palette is not that far apart in RGB space. These "bad results" are much more pronounced when the input image is in color, because three dimensions are being reduced.
Another usage of `--recolor` would be to invert the image colors, by providing `--palette` in reverse. But this is the same as providing the inverted image beforehand.
If you have found other uses for `--recolor`, let me know!
## Other info
To increase the dithering artifacts for aesthetic effect, you can downscale the image before dithering and upscale after. Like if the image is 1000 pixels tall, your command can look like `didder --height 500 --upscale 2 [...]`. Depending on the input image size and what final size you want, you can of course just upscale as well.
## License
This project is licensed under the GPL v3.0. See the [LICENSE](./LICENSE) file for details.

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fake_quantizer.go
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package main
import (
"image"
"image/color"
)
// Like in the dither library, see
// https://github.com/makeworld-the-better-one/dither/blob/3714c39500bc23a87a4fa14053344f201cc5beff/draw.go#L128-L156
// Use for specifying the recolor palette for GIF encoding
// fakeQuantizer implements draw.Quantizer. It ignores the provided image
// and just returns the provided palette each time. This is useful for places that
// only allow you to set the palette through a draw.Quantizer, like the image/gif
// package.
type fakeQuantizer struct {
p []color.Color
}
func (fq *fakeQuantizer) Quantize(p color.Palette, m image.Image) color.Palette {
return fq.p
}

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go.mod
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module github.com/makeworld-the-better-one/didder
go 1.16
require (
github.com/disintegration/imaging v1.6.2
github.com/makeworld-the-better-one/dither/v2 v2.1.0
github.com/urfave/cli/v2 v2.3.0
golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb
)

28
go.sum
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github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d h1:U+s90UTSYgptZMwQh2aRr3LuazLJIa+Pg3Kc1ylSYVY=
github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/disintegration/imaging v1.6.2 h1:w1LecBlG2Lnp8B3jk5zSuNqd7b4DXhcjwek1ei82L+c=
github.com/disintegration/imaging v1.6.2/go.mod h1:44/5580QXChDfwIclfc/PCwrr44amcmDAg8hxG0Ewe4=
github.com/makeworld-the-better-one/dither/v2 v2.1.0 h1:ihYRtKQDkZwZutaCeRf1vYaq1Jqoy2mZGZR8BNZZK2I=
github.com/makeworld-the-better-one/dither/v2 v2.1.0/go.mod h1:VBtN8DXO7SNtyGmLiGA7IsFeKrBkQPze1/iAeM95arc=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/russross/blackfriday/v2 v2.0.1 h1:lPqVAte+HuHNfhJ/0LC98ESWRz8afy9tM/0RK8m9o+Q=
github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
github.com/shurcooL/sanitized_anchor_name v1.0.0 h1:PdmoCO6wvbs+7yrJyMORt4/BmY5IYyJwS/kOiWx8mHo=
github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
github.com/urfave/cli/v2 v2.3.0 h1:qph92Y649prgesehzOrQjdWyxFOp/QVM+6imKHad91M=
github.com/urfave/cli/v2 v2.3.0/go.mod h1:LJmUH05zAU44vOAcrfzZQKsZbVcdbOG8rtL3/XcUArI=
golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb h1:fqpd0EBDzlHRCjiphRR5Zo/RSWWQlWv34418dnEixWk=
golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/yaml.v2 v2.2.3/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

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main.go
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package main
import (
"errors"
"fmt"
"os"
"strings"
"github.com/urfave/cli/v2"
)
// Set by compiler, see Makefile
var (
version = "v1.0.0"
commit = "unknown"
builtBy = "unknown"
)
func main() {
var (
matrixTypesDesc = "This only takes one argument, but there a few types available:\n" +
helpList(1,
"A preprogrammed matrix name",
"Inline JSON of a custom matrix",
"Or a path to JSON for your custom matrix. '-' means stdin.",
) + "\n"
decimalOrPercent = ", using a decimal or percentage."
caseInsensitiveNames = "\nTheir names are case-insensitive, and hyphens and underscores are treated the same."
description = `
Colors (for --palette and --recolor) are entered as a single quoted argument.
They can be separated by spaces and commas. Colors can be formatted as hex
codes (case-insensitive, with or without the '#'), a single number from 0-255
for grayscale, or a color name from the SVG 1.1 spec (aka the HTML or W3C
color names).
Images are converted to grayscale automatically if the palette is grayscale.
This produces more correct results.
Decimal range is -1.0 to 1.0. Percentage range is -100% or 100%.
The input file path can also be parsed as a glob. This will only happen if the
path contains an asterisk. For example -i '*.jpg' will select all the .jpg
files in the current directory as input. See this page for more info on glob
pattern matching: https://golang.org/pkg/path/filepath/#Match`
)
app := &cli.App{
Name: "didder",
Usage: "dither images with a variety of algorithms and processing options.",
Description: description,
UseShortOptionHandling: true,
Flags: []cli.Flag{
&cli.StringFlag{
Name: "strength",
Aliases: []string{"s"},
Usage: "set strength of dithering" + decimalOrPercent + " Exceeding the range will work. A zero value will be ignored.",
},
&cli.UintFlag{
Name: "threads",
Aliases: []string{"j"},
Usage: "set number of threads for ordered dithering",
},
&cli.StringFlag{
Name: "palette",
Aliases: []string{"p"},
Usage: "set color palette used for dithering",
Required: true,
},
&cli.BoolFlag{
Name: "grayscale",
Usage: "make input image(s) grayscale before dithering",
},
&cli.StringFlag{
Name: "saturation",
Usage: "change input image(s) saturation before dithering" + decimalOrPercent,
},
&cli.StringFlag{
Name: "brightness",
Usage: "change input image(s) brightness before dithering" + decimalOrPercent,
},
&cli.StringFlag{
Name: "contrast",
Usage: "change input image(s) contrast before dithering" + decimalOrPercent,
},
&cli.StringFlag{
Name: "recolor",
Aliases: []string{"r"},
Usage: "set color palette used for replacing the dithered color palette after dithering",
},
&cli.BoolFlag{
Name: "no-exif-rotation",
Usage: "disable using the EXIF rotation flag to rotate the image before processing",
},
&cli.StringFlag{
Name: "format",
Aliases: []string{"f"},
Usage: "set output file format. Valid options are png and gif. It will auto detect from filename when possible.",
Value: "png",
},
&cli.StringFlag{
Name: "out",
Aliases: []string{"o"},
Usage: "set output file path or directory",
Required: true,
},
&cli.StringSliceFlag{
Name: "in",
Aliases: []string{"i"},
Usage: "set input file path, specify multiple times for multiple inputs",
Required: true,
},
&cli.BoolFlag{
Name: "no-overwrite",
Usage: "the command will stop before overwriting an existing file. Files written before this one was encountered will stay in place.",
},
&cli.StringFlag{
Name: "compression",
Aliases: []string{"c"},
Usage: "PNG compression type. Options: 'default', 'no', 'speed', 'size'",
Value: "default",
},
&cli.Float64Flag{
Name: "fps",
Usage: "set frames per second for animated GIF output",
},
&cli.UintFlag{
Name: "loop",
Usage: "number of times the animated GIF output should loop, 0 is infinite",
},
&cli.UintFlag{
Name: "width",
Aliases: []string{"x"},
Usage: "set the width the input image(s) will be resized to, BEFORE dithering. Aspect ratio will be maintained if --height is not specified",
},
&cli.UintFlag{
Name: "height",
Aliases: []string{"y"},
Usage: "set the height the input image(s) will be resized to, BEFORE dithering. Aspect ratio will be maintained if --width is not specified",
},
&cli.UintFlag{
Name: "upscale",
Aliases: []string{"u"},
Usage: "scale image up AFTER dithering. So '2' will make the output 2 times as big as the input. Integer only.",
Value: 1,
},
&cli.BoolFlag{
Name: "version",
Aliases: []string{"v"},
Usage: "get version info",
},
},
Commands: []*cli.Command{
{
Name: "random",
Usage: "grayscale and RGB random dithering",
Description: "Specify two arguments (min and max) for RGB or grayscale, or 6 (min/max for each channel) to control each RGB channel.\nArguments can be separated by commas or spaces. -0.5,0.5 is a good default.",
Flags: []cli.Flag{
&cli.Int64Flag{
Name: "seed",
Aliases: []string{"s"},
Usage: "set the seed for randomization. This will also only use one thread, to keep output deterministic",
},
},
UseShortOptionHandling: true,
Action: random,
SkipFlagParsing: true, // Allow for numbers that start with a negative
},
{
Name: "bayer",
Usage: "Bayer matrix ordered dithering",
Description: "Two arguments, for the X and Y dimension of the matrix. They can be separated by a space, comma, or 'x'.\nBoth arguments must be a power of two, with the exception of: 3x5, 5x3, and 3x3.",
UseShortOptionHandling: true,
Action: bayer,
},
{
Name: "odm",
Usage: "Ordered Dither Matrix",
Description: "Select or provide an ordered dithering matrix. " + matrixTypesDesc +
"Here are all the built-in ordered dithering matrices. You can find details on these matrices here:\nhttps://github.com/makeworld-the-better-one/dither/blob/v2.0.0/ordered_ditherers.go\n\n" +
helpList(1,
"ClusteredDot4x4",
"ClusteredDotDiagonal8x8",
"Vertical5x3",
"Horizontal3x5",
"ClusteredDotDiagonal6x6",
"ClusteredDotDiagonal8x8_2",
"ClusteredDotDiagonal16x16",
"ClusteredDot6x6",
"ClusteredDotSpiral5x5",
"ClusteredDotHorizontalLine",
"ClusteredDotVerticalLine",
"ClusteredDot8x8",
"ClusteredDot6x6_2",
"ClusteredDot6x6_3",
"ClusteredDotDiagonal8x8_3",
) + caseInsensitiveNames,
UseShortOptionHandling: true,
Action: odm,
},
{
Name: "edm",
Usage: "Error Diffusion Matrix",
Description: "Select or provide an error diffusion matrix. " + matrixTypesDesc +
"Here are all the built-in error diffusion matrices. You can find details on these matrices here:\nhttps://github.com/makeworld-the-better-one/dither/blob/v2.0.0/error_diffusers.go\n\n" +
helpList(1,
"Simple2D",
"FloydSteinberg",
"FalseFloydSteinberg",
"JarvisJudiceNinke",
"Atkinson",
"Stucki",
"Burkes",
"Sierra (or Sierra3)",
"TwoRowSierra (or Sierra2)",
"SierraLite (or Sierra2_4A)",
"StevenPigeon",
) + caseInsensitiveNames,
Flags: []cli.Flag{
&cli.BoolFlag{
Name: "serpentine",
Aliases: []string{"s"},
Usage: "enable serpentine dithering",
},
},
UseShortOptionHandling: true,
Action: edm,
},
},
Before: preProcess,
Action: func(c *cli.Context) error {
return errors.New("no command specified")
},
}
// Handle version flag
if len(os.Args) == 2 && (os.Args[1] == "-v" || os.Args[1] == "--version") {
fmt.Println("didder", version)
fmt.Println("Commit:", commit)
fmt.Println("Built by:", builtBy)
return
}
// Hack around issue where required flags are still required even for help
// https://github.com/urfave/cli/issues/1247
if len(os.Args) == 3 {
if os.Args[1] == "h" || os.Args[1] == "help" {
// Like: didder help bayer
for _, c := range app.Commands {
if c.Name == os.Args[2] {
cli.HelpPrinter(os.Stdout, cli.CommandHelpTemplate, c)
return
}
}
fmt.Println("no command with that name")
os.Exit(1)
} else if os.Args[len(os.Args)-1] == "-h" || os.Args[len(os.Args)-1] == "--help" {
// Like: didder bayer --help
for _, c := range app.Commands {
if c.Name == os.Args[1] {
cli.HelpPrinter(os.Stdout, cli.CommandHelpTemplate, c)
return
}
}
fmt.Println("no command with that name")
os.Exit(1)
}
}
err := app.Run(os.Args)
if err != nil {
if len(os.Args) == 1 {
// Just ran the command with no flags
return
}
fmt.Println(err)
os.Exit(1)
}
}
// helpList creates an indented list for the CLI help/usage info.
func helpList(level int, items ...string) string {
ret := ""
for _, item := range items {
ret += strings.Repeat(" ", level) + "- " + item + "\n"
}
return ret
}

488
subcommand_helpers.go
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package main
import (
"errors"
"fmt"
"image"
"image/color"
"image/draw"
"image/gif"
"image/png"
"io"
"math"
"os"
"path/filepath"
"strconv"
"strings"
"github.com/disintegration/imaging"
"github.com/makeworld-the-better-one/dither/v2"
"github.com/urfave/cli/v2"
"golang.org/x/image/colornames"
)
// parsePercentArg takes a string like "0.5" or "50%" and will return a float
// like 50 or 0.5, depending on the second argument. An empty string returns 0.
//
// If `maxOne` is true, then "50%" will return 0.5. Otherwise it will return 50.
func parsePercentArg(arg string, maxOne bool) (float64, error) {
if arg == "" {
return 0, nil
}
if strings.HasSuffix(arg, "%") {
arg = arg[:len(arg)-1]
f64, err := strconv.ParseFloat(arg, 64)
if err != nil {
return 0, err
}
if maxOne {
f64 /= 100.0
}
return f64, nil
}
f64, err := strconv.ParseFloat(arg, 64)
if !maxOne {
f64 *= 100.0
}
return f64, err
}
// globalFlag returns the value of flag at the top level of the command.
// For example, with the command:
// dither --threads 1 edm -s Simple2D
// "threads" is a global flag, and "s" is a flag local to the edm subcommand.
func globalFlag(flag string, c *cli.Context) interface{} {
ancestor := c.Lineage()[len(c.Lineage())-1]
if len(ancestor.Args().Slice()) == 0 {
// When the global context calls this func, the last in the lineage
// has no args for some reason. So return the second-last instead.
return c.Lineage()[len(c.Lineage())-2].Value(flag)
}
return ancestor.Value(flag)
}
// globalIsSet returns a bool indicating whether the provided global flag
// was actually set.
func globalIsSet(flag string, c *cli.Context) bool {
ancestor := c.Lineage()[len(c.Lineage())-1]
if len(ancestor.Args().Slice()) == 0 {
// See globalFlag
return c.Lineage()[len(c.Lineage())-2].IsSet(flag)
}
return ancestor.IsSet(flag)
}
// parseArgs takes arguments and splits them using the provided split characters.
func parseArgs(args []string, splitRunes string) []string {
finalArgs := make([]string, 0)
for _, arg := range args {
finalArgs = append(finalArgs, strings.FieldsFunc(arg, func(c rune) bool {
for _, c2 := range splitRunes {
if c == c2 {
return true
}
}
return false
})...)
}
return finalArgs
}
func hex2Color(hex string) (color.RGBA, error) {
// Modified from https://github.com/lucasb-eyer/go-colorful/blob/v1.2.0/colors.go#L333
format := "%02x%02x%02x"
var r, g, b uint8
n, err := fmt.Sscanf(strings.ToLower(hex), format, &r, &g, &b)
if err != nil {
return color.RGBA{}, err
}
if n != 3 {
return color.RGBA{}, fmt.Errorf("%v is not a hex color", hex)
}
return color.RGBA{r, g, b, 255}, nil
}
// parseColors takes args and turns them into a color slice. All returned
// colors are guaranteed to only be color.RGBA.
func parseColors(flag string, c *cli.Context) ([]color.Color, error) {
args := parseArgs([]string{globalFlag(flag, c).(string)}, " ,#")
colors := make([]color.Color, len(args))
for i, arg := range args {
// Try to parse as hex, then grayscale, then HTML colors, then fail
hexColor, err := hex2Color(arg)
if err == nil {
colors[i] = hexColor
continue
}
n, err := strconv.Atoi(arg)
if err == nil {
if n > 255 || n < 0 {
return nil, fmt.Errorf("%s: single numbers like %d must be in the range 0-255", flag, n)
}
colors[i] = color.RGBA{uint8(n), uint8(n), uint8(n), 255}
continue
}
htmlColor, ok := colornames.Map[strings.ToLower(arg)]
if ok {
colors[i] = htmlColor
continue
}
return nil, fmt.Errorf("%s: %s not recognized as a hex code, number 0-255, or HTML color name", flag, arg)
}
return colors, nil
}
// getInputImage takes an input image arg and returns an image that has
// modifications applied.
func getInputImage(arg string, c *cli.Context) (image.Image, error) {
var img image.Image
var err error
if arg == "-" {
img, err = imaging.Decode(os.Stdin, autoOrientation)
} else {
img, err = imaging.Open(arg, autoOrientation)
}
if err != nil {
return nil, err
}
if width != 0 || height != 0 {
// Box sampling is quick and fast, and better then others at downscaling
// Downscaling will be a much more common use case for pre-dither scaling
// then upscaling
// https://pkg.go.dev/github.com/disintegration/imaging#ResampleFilter
// https://en.wikipedia.org/wiki/Image_scaling#Box_sampling
img = imaging.Resize(img, width, height, imaging.Box)
}
if grayscale {
img = imaging.Grayscale(img)
}
if saturation != 0 {
img = imaging.AdjustSaturation(img, saturation)
}
if contrast != 0 {
img = imaging.AdjustContrast(img, contrast)
}
if brightness != 0 {
img = imaging.AdjustBrightness(img, brightness)
}
return img, nil
}
// From dither library
func copyImage(dst draw.Image, src image.Image) {
draw.Draw(dst, src.Bounds(), src, src.Bounds().Min, draw.Src)
}
func copyOfImage(img image.Image) *image.RGBA {
dst := image.NewRGBA(img.Bounds())
copyImage(dst, img)
return dst
}
///////
// recolor will recolor the image pixels if necessary. It should be called
// before writing any image. It should only be given a dithered image.
// It will copy an image if it cannot draw on it.
//
// If the input image is *image.Paletted, the output will always be of that type too.
func recolor(src image.Image) image.Image {
if len(recolorPalette) == 0 {
return src
}
// Modified and returned value
var img draw.Image
// Map of original palette colors to recolor colors
paletteToRecolor := make(map[color.Color]color.Color)
for i, c := range palette {
paletteToRecolor[c] = recolorPalette[i]
}
// Fast path for paletted images
if p, ok := src.(*image.Paletted); ok {
// For each color in the image palette, replace it with the equivalent
// recolor palette color
for i, c := range p.Palette {
p.Palette[i] = paletteToRecolor[color.RGBAModel.Convert(c)]
}
return p
}
var ok bool
if img, ok = src.(draw.Image); !ok {
// Can't be changed
// Instead make a copy and recolor and return that
img = copyOfImage(src)
}
// Swap each image pixel
b := img.Bounds()
for y := b.Min.Y; y < b.Max.Y; y++ {
for x := b.Min.X; x < b.Max.X; x++ {
// Image pixel -> convert to RGBA -> find palette index using `m`
// -> find recolor palette color using index -> set color
img.Set(x, y, paletteToRecolor[color.RGBAModel.Convert(img.At(x, y))])
}
}
return img
}
// postProcImage post-processes the image, applying recolor and upscaling.
//
// If the input image is *image.Paletted, the output will always be of that type too.
func postProcImage(img image.Image) image.Image {
img = recolor(img)
var palette color.Palette
if p, ok := img.(*image.Paletted); ok {
palette = p.Palette
}
if upscale == 1 {
return img
}
img = imaging.Resize(
img,
img.Bounds().Dx()*upscale,
0,
imaging.NearestNeighbor,
)
if len(palette) == 0 {
return img
}
pi := image.NewPaletted(img.Bounds(), palette)
copyImage(pi, img)
return pi
}
// processImages dithers all the input images and writes them.
// It handles all image I/O.
func processImages(d *dither.Ditherer, c *cli.Context) error {
outPath := globalFlag("out", c).(string)
// Setup for if it's an animated GIF output
// Overall adapted from:
// https://github.com/makeworld-the-better-one/dither/blob/v2.0.0/examples/gif_animation.go
isAnimGIF := len(inputImages) > 1 && outFormat == "gif" && !outIsDir
var frames []*image.Paletted
if isAnimGIF {
frames = make([]*image.Paletted, len(inputImages))
}
var delays []int
var animGIF gif.GIF
if isAnimGIF {
if !globalIsSet("fps", c) {
return errors.New("output will be animated GIF, but --fps flag is not set")
}
delays = make([]int, len(inputImages))
for i := range delays {
// Round to the nearest possible frame rate supported by the GIF format
// See for details: https://superuser.com/a/1449370
// A rolling average is not done because it's harder to code and looks
// bad: https://superuser.com/q/1459724
//
// Lowest allowed delay is 1, or 100 FPS.
delays[i] = int(math.Max(math.Round(100.0/globalFlag("fps", c).(float64)), 1))
}
loopCount := int(globalFlag("loop", c).(uint))
if loopCount == 1 {
// Looping once is set using -1 in the image/gif library
loopCount = -1
} else if loopCount != 0 {
// The CLI flag is equal to the number of times looped
// But for gif.GIF.LoopCount, "the animation is looped LoopCount+1 times."
loopCount -= 1
}
animGIF = gif.GIF{
Image: frames,
Delay: delays,
LoopCount: loopCount,
}
}
// Go through images and dither (and write if not an animated GIF)
for i, inputPath := range inputImages {
img, err := getInputImage(inputPath, c)
if err != nil {
return fmt.Errorf("error loading '%s': %w", inputPath, err)
}
if isAnimGIF {
if i == 0 {
// Use the config of the first image for the animated GIF
var config image.Config
frames[0], config = d.DitherPalettedConfig(img)
frames[0] = postProcImage(frames[0]).(*image.Paletted)
if len(recolorPalette) == 0 {
animGIF.Config = config
} else {
// Same config as the Ditherer would give, but with the recolor palette
animGIF.Config = image.Config{
ColorModel: color.Palette(recolorPalette),
Width: frames[0].Bounds().Dx(),
Height: frames[0].Bounds().Dy(),
}
}
continue
}
// Later frames
if upscale == 1 && !img.Bounds().Eq(frames[0].Bounds()) {
// Upscale check is needed because otherwise frames[0] will be upscaled and not match
return fmt.Errorf(
"image '%s' isn't the same size as '%s', all sizes must match to create an animated GIF",
inputPath, inputImages[0],
)
}
frames[i] = d.DitherPaletted(img)
frames[i] = postProcImage(frames[i]).(*image.Paletted)
// Do bounds check now, if it didn't happen before because of upscaling
if upscale != 1 && !frames[i].Bounds().Eq(frames[0].Bounds()) {
return fmt.Errorf(
"image '%s' isn't the same size as '%s', all sizes must match to create an animated GIF",
inputPath, inputImages[0],
)
}
continue
}
// Not an animated GIF
// Write out the image now
// (partially copied below, outside the loop)
var file io.WriteCloser
var path string
if outPath == "-" {
file = os.Stdout
path = "stdout"
} else {
if outIsDir {
// Inside output directory
// Same name as input file but potentially different extension
path = filepath.Join(
outPath,
strings.TrimSuffix(filepath.Base(inputPath), filepath.Ext(inputPath))+"."+outFormat,
)
} else {
// Output file path
path = outPath
}
file, err = os.OpenFile(path, outFileFlags, 0644)
if err != nil {
return fmt.Errorf("'%s': %w", path, err)
}
}
if outFormat == "png" {
img = postProcImage(d.Dither(img))
err = (&png.Encoder{CompressionLevel: compLevel}).Encode(file, img)
if err != nil {
defer file.Close() // Keep (possibly stdout) open to write error messages then close
return fmt.Errorf("error writing PNG to '%s': %w", path, err)
}
file.Close()
} else {
// Output static GIF
// Adapted from:
// https://github.com/makeworld-the-better-one/dither/blob/v2.0.0/examples/gif_image.go
if !postProcNeeded {
// No post
// GIF encoder calls the ditherer
err = gif.Encode(
file, img,
&gif.Options{
NumColors: len(palette),
Quantizer: d,
Drawer: d,
},
)
} else {
// Dither and post-process first, and use recolor palette if needed
// The gif package will not change the image if it's *image.Paletted
// So even though Drawer is not set to the ditherer it'll be fine,
// and the default FloydSteinberg Drawer won't be used
img = postProcImage(d.DitherPaletted(img))
var quantizer draw.Quantizer
if len(recolorPalette) == 0 {
quantizer = d
} else {
quantizer = &fakeQuantizer{recolorPalette}
}
err = gif.Encode(
file, img,
&gif.Options{
NumColors: len(recolorPalette),
Quantizer: quantizer,
},
)
}
if err != nil {
defer file.Close()
return fmt.Errorf("error writing GIF to '%s': %w", path, err)
}
file.Close()
}
}
// Either all images have been written and everything is done, or the animated GIF
// needs to be saved.
if !isAnimGIF {
return nil
}
// Partially copied from above
var file io.WriteCloser
var path string
var err error
if outPath == "-" {
file = os.Stdout
path = "stdout"
} else {
// Output file path
path = outPath
file, err = os.OpenFile(path, outFileFlags, 0644)
if err != nil {
return fmt.Errorf("'%s': %w", path, err)
}
}
err = gif.EncodeAll(file, &animGIF)
if err != nil {
defer file.Close()
return fmt.Errorf("error writing GIF to '%s': %w", path, err)
}
file.Close()
return nil
}

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subcommands.go
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package main
import (
"encoding/json"
"errors"
"fmt"
"image/color"
"image/png"
"io/ioutil"
"math/rand"
"os"
"path/filepath"
"runtime"
"strconv"
"strings"
"time"
"github.com/disintegration/imaging"
"github.com/makeworld-the-better-one/dither/v2"
"github.com/urfave/cli/v2"
)
const (
unsupportedFormat string = "'%s' is an unsupported format, only 'png' or 'gif' are accepted"
)
var (
// palette stores the palette colors. It's set after pre-processing.
// Guaranteed to only hold color.RGBA.
palette []color.Color
// recolorPalette stores the recolor palette colors. It's set after pre-processing.
// Guaranteed to only hold color.RGBA.
recolorPalette []color.Color
grayscale bool
// Range -100,100
saturation float64
brightness float64
contrast float64
autoOrientation imaging.DecodeOption
inputImages []string
outFormat string // "png" or "gif"
outIsDir bool
compLevel png.CompressionLevel
outFileFlags int // For os.OpenFile
width int
height int
// upscale will always be 1 or above
upscale int
ditherer *dither.Ditherer
// range [-1, 1]
strength float32
// Is post-processing needed?
postProcNeeded bool
)
// preProcess is automatically called by the app before anything else.
// It's run in the global context.
func preProcess(c *cli.Context) error {
runtime.GOMAXPROCS(int(c.Uint("threads")))
var err error
palette, err = parseColors("palette", c)
if err != nil {
return err
}
if len(palette) < 2 {
return errors.New("the palette must have at least two colors")
}
if c.String("recolor") != "" {
recolorPalette, err = parseColors("recolor", c)
if err != nil {
return err
}
if len(recolorPalette) != len(palette) {
return errors.New("recolor palette must have the same number of colors as the initial palette")
}
}
// Check if palette is grayscale and make image grayscale
// Or if the user forces it
grayscale = true
if !c.Bool("grayscale") {
// Grayscale isn't specified by the user
// So check to see if palette is grayscale
for _, c := range palette {
r, g, b, _ := c.RGBA()
if r != g || g != b {
grayscale = false
}
}
}
saturation, err = parsePercentArg(c.String("saturation"), false)
if err != nil {
return fmt.Errorf("saturation: %w", err)
}
if saturation <= -100 {
grayscale = true
saturation = 0
}
brightness, err = parsePercentArg(c.String("brightness"), false)
if err != nil {
return fmt.Errorf("brightness: %w", err)
}
contrast, err = parsePercentArg(c.String("contrast"), false)
if err != nil {
return fmt.Errorf("contrast: %w", err)
}
autoOrientation = imaging.AutoOrientation(!c.Bool("no-exif-rotation"))
inputImages = make([]string, 0)
for _, path := range c.StringSlice("in") {
if strings.Contains(path, "*") {
// Parse as glob
paths, err := filepath.Glob(path)
if err != nil {
return fmt.Errorf("bad glob pattern '%s': %w", path, err)
}
inputImages = append(inputImages, paths...)
} else {
inputImages = append(inputImages, path)
}
}
formatVal := c.String("format")
if formatVal != "png" && formatVal != "gif" {
return fmt.Errorf(unsupportedFormat, formatVal)
}
// Figure out output format
outVal := c.String("out")
if outVal == "-" {
// Outputting to stdout, so just use whatever the flag is
outFormat = formatVal
} else {
// Outputting to dir or file
outFI, err := os.Stat(outVal)
if err == nil && outFI.IsDir() {
// Exists and is a directory
// Just use what the flag is
outFormat = formatVal
outIsDir = true
} else {
// Outputting to file, that already exists
// Or something that doesn't exist - assumed to be a file
if !c.IsSet("format") {
// Format wasn't set, so ignore default value of "png"
// Try to figure out format from output filename
ext := strings.TrimPrefix(filepath.Ext(outVal), ".")
if ext == "png" || ext == "gif" {
// Acceptable extension
outFormat = ext
} else if ext == "" {
// No extension, use default format
outFormat = "png"
} else {
// Unsupported extension and no format flag override
return fmt.Errorf(unsupportedFormat, ext)
}
} else {
// Format flag was set, so ignore what the file looks like
outFormat = formatVal
}
}
}
// Multiple input images are only valid if the output is GIF,
// or if the output points to a directory.
if len(inputImages) > 1 && (outFormat != "gif" && !outIsDir) {
return fmt.Errorf("multiple input images are only allowed if the output format is GIF, or an existing directory")
}
if outFormat == "gif" && len(palette) > 256 {
return errors.New("the GIF format only supports 256 colors or less in the palette")
}
// Set PNG compression type
switch c.String("compression") {
case "default":
compLevel = png.DefaultCompression
case "no":
compLevel = png.NoCompression
case "speed":
compLevel = png.BestSpeed
case "size":
compLevel = png.BestCompression
default:
return fmt.Errorf("invalid compression type '%s'", c.String("compression"))
}
if c.Bool("no-overwrite") {
outFileFlags = os.O_WRONLY | os.O_CREATE | os.O_EXCL
} else {
outFileFlags = os.O_WRONLY | os.O_CREATE | os.O_TRUNC
}
// Set here for convenience
width = int(c.Uint("width"))
height = int(c.Uint("height"))
upscale = int(c.Uint("upscale"))
if upscale == 0 {
// Invalid
upscale = 1
}
ditherer = dither.NewDitherer(palette)
tmp, err := parsePercentArg(c.String("strength"), true)
if err != nil {
return fmt.Errorf("strength: %w", err)
}
strength = float32(tmp)
if strength == 0 {
// Ignore
strength = 1
}
if len(recolorPalette) != 0 || upscale > 1 {
postProcNeeded = true
}
return nil
}
func random(c *cli.Context) error {
args := parseArgs(c.Args().Slice(), " ,")
// Manually parse out --seed, -s flag
// The manual parsing is done to allow for numbers that start with a negative
// which would otherwise be interpreted as flags
seedIsSet := false
var seed int64
if len(args) >= 1 {
if args[0] == "--seed" || args[0] == "-s" {
if len(args) >= 2 {
// Parse and set seed value
var err error
seed, err = strconv.ParseInt(args[1], 10, 64)
if err != nil {
return fmt.Errorf("couldn't parse seed value: %w", err)
}
seedIsSet = true
args = args[2:]
} else {
// Seed flag but no value after it
return errors.New("no value after seed flag")
}
} else if args[0] == "--help" || args[0] == "-h" {
// Display the help
return cli.ShowCommandHelp(c, "random")
}
}
if len(args) != 2 && len(args) != 6 {
return errors.New("random needs 2 or 6 arguments")
}
floatArgs := make([]float32, len(args))
for i, arg := range args {
f64, err := parsePercentArg(arg, true)
if err != nil {
return err
}
floatArgs[i] = float32(f64)
}
if seedIsSet {
rand.Seed(seed)
} else {
// Seed with something that won't repeat next use
rand.Seed(time.Now().UnixNano())
}
if len(floatArgs) == 2 {
if grayscale || saturation <= -100 {
ditherer.Mapper = dither.RandomNoiseGrayscale(floatArgs[0], floatArgs[1])
} else {
// Use the two arguments for all channels
ditherer.Mapper = dither.RandomNoiseRGB(floatArgs[0], floatArgs[1], floatArgs[0], floatArgs[1], floatArgs[0], floatArgs[1])
}
} else {
ditherer.Mapper = dither.RandomNoiseRGB(floatArgs[0], floatArgs[1], floatArgs[2], floatArgs[3], floatArgs[4], floatArgs[5])
}
if seedIsSet {
// Make deterministic
ditherer.SingleThreaded = true
}
err := processImages(ditherer, c)
if err != nil {
return err
}
return nil
}
func bayer(c *cli.Context) error {
args := parseArgs(c.Args().Slice(), " ,x")
if len(args) != 2 {
return errors.New("bayer needs 2 arguments exactly")
}
uintArgs := make([]uint, 2)
for i, arg := range args {
u64, err := strconv.ParseUint(arg, 10, 0)
if err != nil {
return err
}
uintArgs[i] = uint(u64)
}
// Validate args to prevent dither.Bayer from panicking
x, y := uintArgs[0], uintArgs[1]
if x == 0 || y == 0 {
return errors.New("neither dimension can be 0")
}
if x == 1 && y == 1 {
return errors.New("a 1x1 matrix will not dither the image")
}
if ((x&(x-1)) != 0 || (y&(y-1)) != 0) && // Power of two?
!((x == 3 && y == 3) || (x == 5 && y == 3) || (x == 3 && y == 5)) { // Exceptions
// Not a power of two, and not an exception
return errors.New("both dimensions must be powers of two")
}
ditherer.Mapper = dither.Bayer(x, y, strength)
err := processImages(ditherer, c)
if err != nil {
return err
}
return nil
}
var odmName = map[string]dither.OrderedDitherMatrix{
"clustereddot4x4": dither.ClusteredDot4x4,
"clustereddotdiagonal8x8": dither.ClusteredDotDiagonal8x8,
"vertical5x3": dither.Vertical5x3,
"horizontal3x5": dither.Horizontal3x5,
"clustereddotdiagonal6x6": dither.ClusteredDotDiagonal6x6,
"clustereddotdiagonal8x8_2": dither.ClusteredDotDiagonal8x8_2,
"clustereddotdiagonal16x16": dither.ClusteredDotDiagonal16x16,
"clustereddot6x6": dither.ClusteredDot6x6,
"clustereddotspiral5x5": dither.ClusteredDotSpiral5x5,
"clustereddothorizontalline": dither.ClusteredDotHorizontalLine,
"clustereddotverticalline": dither.ClusteredDotVerticalLine,
"clustereddot8x8": dither.ClusteredDot8x8,
"clustereddot6x6_2": dither.ClusteredDot6x6_2,
"clustereddot6x6_3": dither.ClusteredDot6x6_3,
"clustereddotdiagonal8x8_3": dither.ClusteredDotDiagonal8x8_3,
}
func odm(c *cli.Context) error {
args := c.Args().Slice()
if len(args) != 1 {
return errors.New("odm only accepts one argument")
}
var matrix dither.OrderedDitherMatrix
matrix, ok := odmName[strings.ReplaceAll(strings.ToLower(args[0]), "-", "_")]
if !ok {
// Either inline JSON, path to file, or an error
err := json.Unmarshal([]byte(args[0]), &matrix)
if err != nil {
bytes, err := ioutil.ReadFile(args[0])
if err != nil {
return errors.New("couldn't process argument as matrix name, inline JSON, or path to accessible JSON file")
}
err = json.Unmarshal(bytes, &matrix)
if err != nil {
return errors.New("couldn't process argument as matrix name, inline JSON, or path to accessible JSON file")
}
}
// Validate matrix
if matrix.Max == 0 {
return errors.New("the max value of the matrix cannot be 0")
}
if len(matrix.Matrix) == 0 {
return errors.New("matrix is empty")
}
// Is it rectangular?
width := len(matrix.Matrix[0])
if width == 0 {
return errors.New("matrix has empty row")
}
for _, row := range matrix.Matrix {
if len(row) != width {
return errors.New("matrix is not rectangular, all rows must be the same length")
}
}
}
ditherer.Mapper = dither.PixelMapperFromMatrix(matrix, strength)
err := processImages(ditherer, c)
if err != nil {
return err
}
return nil
}
var edmName = map[string]dither.ErrorDiffusionMatrix{
"simple2d": dither.Simple2D,
"floydsteinberg": dither.FloydSteinberg,
"falsefloydsteinberg": dither.FalseFloydSteinberg,
"jarvisjudiceninke": dither.JarvisJudiceNinke,
"atkinson": dither.Atkinson,
"stucki": dither.Stucki,
"burkes": dither.Burkes,
"sierra": dither.Sierra,
"sierra3": dither.Sierra3,
"tworowsierra": dither.TwoRowSierra,
"sierralite": dither.SierraLite,
"sierra2_4a": dither.Sierra2_4A,
"stevenpigeon": dither.StevenPigeon,
}
func edm(c *cli.Context) error {
args := c.Args().Slice()
if len(args) != 1 {
return errors.New("edm only accepts one argument")
}
var matrix dither.ErrorDiffusionMatrix
matrix, ok := edmName[strings.ReplaceAll(strings.ToLower(args[0]), "-", "_")]
if !ok {
// Either inline JSON, path to file, or an error
err := json.Unmarshal([]byte(args[0]), &matrix)
if err != nil {
bytes, err := ioutil.ReadFile(args[0])
if err != nil {
return errors.New("couldn't process argument as matrix name, inline JSON, or path to accessible JSON file")
}
err = json.Unmarshal(bytes, &matrix)
if err != nil {
return errors.New("couldn't process argument as matrix name, inline JSON, or path to accessible JSON file")
}
}
// Validate matrix
if len(matrix) == 0 {
return errors.New("matrix is empty")
}
// Is it rectangular?
width := len(matrix[0])
if width == 0 {
return errors.New("matrix has empty row")
}
for _, row := range matrix {
if len(row) != width {
return errors.New("matrix is not rectangular, all rows must be the same length")
}
}
}
ditherer.Matrix = dither.ErrorDiffusionStrength(matrix, strength)
if c.Bool("serpentine") {
ditherer.Serpentine = true
}
err := processImages(ditherer, c)
if err != nil {
return err
}
return nil
}
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