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x/image/webp: WebP decode contrast issue #40173

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AliFlux opened this issue Jul 12, 2020 · 12 comments
Open

x/image/webp: WebP decode contrast issue #40173

AliFlux opened this issue Jul 12, 2020 · 12 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Unreleased

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@AliFlux
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AliFlux commented Jul 12, 2020

What version of Go are you using (go version)?

go version go1.13.7 windows/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
set GO111MODULE=off
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Alpha\AppData\Local\go-build
set GOENV=C:\Users\Alpha\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Alpha\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=c:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=c:\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\Alpha\AppData\Local\Temp\go-build034800510=/tmp/go-build -gno-record-gcc-switches

What did you do?

I opened up a webp using go, and saved it back to png, The output was different from the source. Other golang webp decoding packages parsed it correctly.

package main

import (
	"image"
	"image/png"
	"os"

	// you can swap between these two libs, chai2010 is okay
	"golang.org/x/image/webp"
	//"github.com/chai2010/webp"
)

func main() {

	tileStream, _ := os.Open("full.webp")
	tile, _ := webp.Decode(tileStream)
	defer tileStream.Close()

	outputStream, _ := os.Create("full.png")
	png.Encode(outputStream, tile)

	defer outputStream.Close()
}

What did you expect to see?

b(1)

This is the source image, notice the details and the clarity.

What did you see instead?

full

This is the converted, the details are dimmed, the contrast is lower. Other webp decoding libs maintain the contrast.
@gopherbot gopherbot added this to the Unreleased milestone Jul 12, 2020
@agnivade
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/cc @nigeltao

@agnivade agnivade added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jul 12, 2020
@dwbuiten
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dwbuiten commented Jul 22, 2020 •
edited

I'm almost certain this is due to x/image's VP8 decoder (which WebP lossy is internally) not handling the full/limited range flag:

https://github.com/golang/image/blob/69cc3646b96e61de0b417f4815b86c36e65783ee/vp8/decode.go#L332-L336

I'm also not sure if image.YCbCr can even handle full range vs limited range YCbCr content. It certainly can't handle any colorspace but BT.601 (which is fine for WebP, which is always BT.601, but won't hold true for newer formats.)

@AliFlux
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AliFlux commented Aug 3, 2020

Is there any temporary hack that can fix this? I'm using python webp library to write the images.

@bep bep mentioned this issue Aug 31, 2021
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@savtrip
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savtrip commented May 15, 2022

Out of curiosity, did anyone find a work around for this? Should we just use another webp library?

@AliFlux
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AliFlux commented May 15, 2022 •
edited

Yeah, I ended up using chai2010 webp library.

@savtrip
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savtrip commented May 15, 2022 •
edited

@AliFlux thanks ali, appreciate the reply, I’ll try out the library.

By the way, the link you gave is broken, I still found the library though.

@savtrip
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savtrip commented May 23, 2022

Hey guys,

I really wanted to highlight that the problem is much worse when there is an image with a white background, for example, the image below:

Original:

google-search-results-how-to-market-my-business

After:

google-search-results-how-to-market-my-business_hubd5e904f9390325c44b8d7a5d156ca03_33118_1200x0_resize_q75_h2_box_2

I added this because I think it shows the problem more pronounced than the original image submitted by @AliFlux.

And also, a big thank you for all the open source work, I really appreciate it and use most of it in my day to day work. Your work obviously has a massive impact on lives around the world.

@savtrip
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savtrip commented Jun 5, 2022

@nigeltao @agnivade if I investigate myself and create a pull request will it be looked at?

@nigeltao
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nigeltao commented Jun 6, 2022

It will be looked at (if you expliciltly add me to the PR) but:

  1. If it involves modifying the standard library's image or image/color packages (and their YCbCr representations), then there's a higher bar for accepting the pull request.
  2. If it involves general concepts of color correction at the API level (e.g. if it requires the caller passing in a color space somehow) then such API should ideally also work with any future color correction API in the standard library and x/image. Once again, there'd therefore be a higher bar. See x/image/draw: color space-correct interpolation #11420 for a discussion.

@savtrip
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savtrip commented Jun 6, 2022

Awesome, thanks @nigeltao, I appreciate it, I wanted to make sure I didn't spend a bunch of timing creating a solution that has no chance.

@TrentMoyar
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@savtrip are you still working on this issue, because if you aren't I'd be interested in taking over.

@savtrip
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savtrip commented Oct 11, 2022 via email

@seankhliao seankhliao changed the title x/image: WebP decode contrast issue x/image/webp: WebP decode contrast issue Jan 30, 2023
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