Grayscale Selections

Sven Langkamp sven.langkamp at
Tue Jun 28 01:47:04 CEST 2011

On Sun, Jun 26, 2011 at 6:58 PM, Sven Langkamp <sven.langkamp at>wrote:

> On Sun, Jun 26, 2011 at 7:27 AM, Dmitry Kazakov <dimula73 at>wrote:
>> I have now tried the alpha()==grayChannel() by overwriting opacityU8 as
>>> quint8 KoGrayColorSpace::opacityU8(const quint8* U8_pixel) const
>>> {
>>>     return *U8_pixel;
>>> }
>>> Interesting is that gradients works correctly, but paint doesn't respect
>>> the transparent areas of the brush.
>> Does it happen when you paint on the selection? Or when you paint on a
>> regular layer with selection activated? If first, I guess, we need to take a
>> look into the compositioning of an rgb color space into this special color
>> space.
> Regular painting works. It's definitely the rgb on grayscale without alpha.
> That doesn't take the alpha channel into account.

The problem is that we convert the to destination colorspace when bitBlt and
by that the alpha channel gets lost. Any suggestions how that could be
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