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Merge byte swap and unmultiplying loops in ctx.getImageData()

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This commit is contained in:
Anthony Ramine 2018-09-13 16:12:47 +02:00
parent 983a914da3
commit b5c469d52e
2 changed files with 6 additions and 10 deletions
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10
components/script/dom/canvasrenderingcontext2d.rs
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@ -1115,12 +1115,12 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
self.send_canvas_2d_msg(Canvas2dMsg::GetImageData(dest_rect, canvas_size, sender));
let mut data = receiver.recv().unwrap();
// Un-premultiply alpha
// Byte swap and unmultiply alpha.
for chunk in data.chunks_mut(4) {
let alpha = chunk[3] as usize;
chunk[0] = UNPREMULTIPLY_TABLE[256 * alpha + chunk[0] as usize];
chunk[1] = UNPREMULTIPLY_TABLE[256 * alpha + chunk[1] as usize];
chunk[2] = UNPREMULTIPLY_TABLE[256 * alpha + chunk[2] as usize];
let (b, g, r, a) = (chunk[0], chunk[1], chunk[2], chunk[3]);
chunk[0] = UNPREMULTIPLY_TABLE[256 * (a as usize) + r as usize];
chunk[1] = UNPREMULTIPLY_TABLE[256 * (a as usize) + g as usize];
chunk[2] = UNPREMULTIPLY_TABLE[256 * (a as usize) + b as usize];
}
ImageData::new(&self.global(), sw, sh, Some(data.to_vec()))