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Bug 389366 - "Canvas's .getImageData is returning premultiplied alpha pixels" [p=philip@zaynar.demon.co.uk (Philip Taylor) r=vlad a1.9=damons aM9=beltzner]

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This commit is contained in:
reed@reedloden.com 2007-10-26 12:45:20 -07:00
parent 92e2badb9b
commit c03c5d7b82
1 changed files with 12 additions and 0 deletions
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12
content/canvas/src/nsCanvasRenderingContext2D.cpp
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@ -2465,6 +2465,13 @@ nsCanvasRenderingContext2D::GetImageData()
PRUint8 g = *row++;
PRUint8 b = *row++;
#endif
// Convert to non-premultiplied color
if (a != 0) {
r = (r * 255) / a;
g = (g * 255) / a;
b = (b * 255) / a;
}
*dest++ = INT_TO_JSVAL(r);
*dest++ = INT_TO_JSVAL(g);
*dest++ = INT_TO_JSVAL(b);
@ -2588,6 +2595,11 @@ nsCanvasRenderingContext2D::PutImageData()
else if (JSVAL_IS_DOUBLE(va)) ia = (PRUint8) (*JSVAL_TO_DOUBLE(va));
else return NS_ERROR_DOM_SYNTAX_ERR;
// Convert to premultiplied color (losslessly if the input came from getImageData)
ir = (ir*ia + 254) / 255;
ig = (ig*ia + 254) / 255;
ib = (ib*ia + 254) / 255;
#ifdef IS_LITTLE_ENDIAN
*imgPtr++ = ib;
*imgPtr++ = ig;