[Webkit-unassigned] [Bug 42273] Convolution computation causes bad alpha channel values

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=42273





--- Comment #23 from Nikolas Zimmermann <zimmermann at kde.org>  2010-07-15 01:30:00 PST ---
(In reply to comment #22)
>     unsigned char maxAlpha = 255;
>     if (!preserveAlphaValues)
>         maxAlpha = clampRGBAValue(totals[3]);
> 
> Maybe:
> 
>     unsigned char maxAlpha = preserveAlphaValues ? 255 : clampRGBAValue(totals[3]);
> 
> Not sure this is preferred.

Definately, good suggestion.

(In reply to comment #21)
> >     image->set(pixel + 1, preserveAlphaValues ? src->get(pixel) : alpha);
> >     ++pixel;
> 
> Are you sure it is "pixel + 1"? Isn't it just "pixel"? And "pixel++" even shorter.

I think both versions are wrong, this should be correct (please correct me if I'm wrong):

if (preserveAlphaValues) {
     image->set(pixel, src->get(pixel));
     ++pixel;
} else
    image->set(pixel++, alpha);

I find "image->set(pixel++, src->get(pixel));" hard to read, that's why I was suggesting the change.

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