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GetImageData should return un-premultiplied alpha values

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This commit is contained in:
David Zbarsky 2015-08-03 20:09:18 -04:00
parent 1b54e9c30c
commit fee8abe5a2
37 changed files with 12 additions and 181 deletions
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13
components/script/dom/canvasrenderingcontext2d.rs
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@ -901,7 +901,18 @@ impl<'a> CanvasRenderingContext2DMethods for &'a CanvasRenderingContext2D {
self.ipc_renderer
.send(CanvasMsg::Canvas2d(Canvas2dMsg::GetImageData(dest_rect, canvas_size, sender)))
.unwrap();
let data = receiver.recv().unwrap();
let mut data = receiver.recv().unwrap();
// Un-premultiply alpha
// TODO: may want a precomputed un-premultiply table to make this fast.
// https://github.com/servo/servo/issues/6969
for chunk in data.chunks_mut(4) {
let alpha = chunk[3] as f32 / 255.;
chunk[0] = (chunk[0] as f32 / alpha) as u8;
chunk[1] = (chunk[1] as f32 / alpha) as u8;
chunk[2] = (chunk[2] as f32 / alpha) as u8;
}
Ok(ImageData::new(self.global.root().r(), sw.abs().to_u32().unwrap(), sh.abs().to_u32().unwrap(), Some(data)))
}