fix(cli): demultiply tiny skia pixels #14416
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Package Changes Through d3d498dThere are 2 changes which include tauri-cli with patch, @tauri-apps/cli with patch Planned Package VersionsThe following package releases are the planned based on the context of changes in this pull request.
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| // Switch to use `Pixmap::take_demultiplied` in the future when it's published | ||
| // https://github.com/linebender/tiny-skia/blob/624257c0feb394bf6c4d0d688f8ea8030aae320f/src/pixmap.rs#L266 | ||
| let img_buffer = ImageBuffer::from_par_fn(size, size, |x, y| { | ||
| let pixel = pixmap.pixel(x, y).unwrap().demultiply(); | ||
| Rgba([pixel.red(), pixel.green(), pixel.blue(), pixel.alpha()]) | ||
| }); | ||
| DynamicImage::ImageRgba8(img_buffer) |
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So skia by default has all pixels multiplied (whatever that means) so we demultiply all pixels to then be able to multiple the alpha channel specifically later in the same resize function that also multiplies the png alpha channel?
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It seems like that tiny-skia does this, the documentation isn't clear here to be honest, but from the code and how they return &[PremultipliedColorU8], it looks like it (Skia marks this in SkPixmap, SkImageInfo, so it's a different story https://api.skia.org/SkAlphaType_8h.html#ad2e3e94ae1ad3b28c96802b77514ab45)
multiplied (whatever that means)
It's used for calculating filtering internally easier, but when we want the final value, we need to undo that
to then be able to multiple the alpha channel specifically later in the same resize function that also multiplies the png alpha channel
This can be optimized but I honestly don't care enough to do that 😂
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Fix #14351 (comment)
Demultiply tiny skia
Pixmappixel alphas before converting toimage::ImageBuffer