How to convert the color space of a KisPaintDevice?

[Dmitry Kazakov]

On Sun, Apr 24, 2011 at 1:53 AM, JL VT <pentalis at gmail.com> wrote:

> After reading a post in the Krita forums asking for Impasto, I took a look
> at the Phong Bumpmap filter with the intent to fix it.
>
> The filter generates a QImage called "bumpmap", this contains the result of
> the process() method.
>
> Currently, the filter simply uses this QImage:
>     device->convertFromQImage(bumpmap, "", applyRect.topLeft().x(),
> applyRect.topLeft().y());
>
> This will only work if "device" is an RGB 8 color space (or maybe in other
> cases I'm not aware of).
>
> I've been _trying_ to fix this behavior by storing the information
> contained in the QImage in an intermediary RGB 8 KisPaintDevice, and then
> turning this to the colorspace of the target KisPaintDevice...
>
> ...but my attempts have not succeeded, this is an example of what I did to
> replace the former line of code:
>     KisPaintDeviceSP quickHack = new
> KisPaintDevice(KoColorSpaceRegistry::instance()->rgb8());
>     quickHack->convertFromQImage(bumpmap, "");
>     KisPainter painter(device);
>     painter.bitBlt(applyRect.topLeft(), quickHack, applyRect);
>
> In theory, this should work. I _thought_ that painter.bitBlt would convert
> the RGB 8 information into whatever colorspace device is using. But...
> this didn't work.
> With this new code, I only get the expected output from the filter if my
> image uses an RGB 8 colorspace. With RGB 16 I get garbage, and with other
> colorspaces I get a crash (I think the crash is a bug from the UI that I
> need to fix, so I'm just testing with RGB 16 for now). So everything is like
> before, no improvement.
>
> Any idea of what I'm doing wrong?.
> I need a way to turn an RGB 8 bitmap into any other colorspace, I'm sure
> Krita already handles that, but I don't know how to turn that RGB 8 data
> into the other colorspaces.
>
> I am stuck here, so help is greatly appreciated.
>

I didn't understand exactly what you need, but i guess the following is what
you are doing:

KisPaintDeviceSP device = new
KisPaintDevice(KoColorSpaceRegistry::instance()->rgb8());
device->convertFromQImage(bumpmap, "");
device->convertTo(yourDesiredColorSpace);

Btw, the code you wrote above should work as well, but less efficiently. If
it doesn't, it would be good to make a testcase in KisPainterTest.

-- 
Dmitry Kazakov
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