[BUG] Webp image color change after resize

[MichaelLogutov]

Description

When loading webp image and saving it in jpg without any transformation all colors preserved correctly. But when scale transformation applied colors became darker.

I've tried it on SkiaSharp 2.88.7 and 3.0.0-preview.2.1

Here the source webp image: test.zip Here the results.

Not scaled: Scaled:

Code

using var bitmap = SKBitmap.Decode(@"c:\Temp\test.webp");

using var bitmap2 = new SKBitmap(new SKImageInfo(bitmap.Info.Width / 2, bitmap.Info.Height / 2));
bitmap.ScalePixels(bitmap2, new SKSamplingOptions(SKFilterMode.Nearest, SKMipmapMode.Nearest));

using (var file = new SKFileWStream(@"c:\Temp\test-output-not-scaled.jpg"))
    bitmap.Encode(file, SKEncodedImageFormat.Jpeg, 100);

using (var file = new SKFileWStream(@"c:\Temp\test-output-scaled.jpg"))
    bitmap2.Encode(file, SKEncodedImageFormat.Jpeg, 100);

Expected Behavior

No response

Actual Behavior

No response

Version of SkiaSharp

3.x (Alpha)

Last Known Good Version of SkiaSharp

2.88.2 (Previous)

IDE / Editor

Other (Please indicate in the description)

Platform / Operating System

Linux, Windows

Platform / Operating System Version

No response

Devices

No response

Relevant Screenshots

No response

Relevant Log Output

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct

[TommiGustafsson-HMP]

I think the problem is that your original picture has a color profile, which is lost at some point. If you open your original picture in Photoshop (Elements) and Convert Color Profile -> Remove Profile, the same thing as reported here will happen.

[MichaelLogutov]

Yeah, I think you right. But I can't see why scaling do this.

[TommiGustafsson-HMP]

There seems to be a question on this on StackOverflow: https://stackoverflow.com/questions/50399279/skiasharp-save-image-with-icc-profile

[MichaelLogutov]

That was it. Thanks! Basically, the fix was using image info from original image, thus using it's color space:

using var bitmap = SKBitmap.Decode(@"c:\Temp\test.webp");

using var bitmap2 = new SKBitmap(bitmap.Info.WithSize(bitmap.Info.Width / 2, bitmap.Info.Height / 2));
bitmap.ScalePixels(bitmap2, new SKSamplingOptions(SKFilterMode.Nearest, SKMipmapMode.Nearest));

using (var file = new SKFileWStream(@"c:\Temp\test-output-not-scaled.jpg"))
    bitmap.Encode(file, SKEncodedImageFormat.Jpeg, 100);

using (var file = new SKFileWStream(@"c:\Temp\test-output-scaled.jpg"))
    bitmap2.Encode(file, SKEncodedImageFormat.Jpeg, 100);