Hey Vade, Sorry for taking so long to get back to you on this.
On Aug 19, 2009, at 12:41 PM, vade wrote:
hello
Id love some clarification on how the colorspace: parameter on the
various methods in QC work.
for lockTextureRepresentationWithColorSpace:forBounds on an
QCPlugInInputImageSource, does the colorspace method decide the
source colorspace of the image, or the destination colorspace? ie:
QC is going to do a conversion from whatever colorspace the image is
marked as into what you request. You should request it in the format
you want and don't do any conversion in your plugin.
a) (source) interpret this image as <some colorspace> and convert it
to RGB since its going to be a texture and used in GL.
b) (destination) interpret this image in its native colorspace and
convert it to <some colorspace> ?
Similarly, for: QCPlugins
outputImageProviderFromTextureWithPixelFormat:pixelsWide:pixelsHigh:name:flipped:releaseCallback:releaseContext:colorSpace:shouldColorMatch
method
does this take a texture, assumed to be in RGB, and set it to be
<some colorspace> or does it take a texture, assumed to be <some
colorspace> and convert it to RGB, or does it take anything, as
anything, and just set a marker to be <some colorspace> to be dealt
with at a later stage?
Here you are creating an image and tagging it with a marker. The
buffer of memory could be any colorspace, so you have to tell QC how
to treat those bytes. Again you should not color correct yourself and
then mark it with the new colorspace, let QC do any necessary
conversions.
While we are on the topic, I would love some clarification:
Is there a default/native color space to QC? I would wager yes, and
that its RGB Linear since QC operates in GL land, and that RGB
linear is (am I correct) the assumed default colorspace of GL, or is
the 'native' colorspace whatever the QCRenderer in question was
initted with?
Color isn't really my area of expertise but I do recall that QC
requires an RGB color model. Within the RGB space QC tries not to
impose any color assumptions until a buffer needs to be passed to
CoreImage or OpenGL which require Linear. An image is like a recipe,
it has a buffer and a list of transformations and color correction can
be one of those transformations. Once it has been asked to draw, it
will apply all the transformations on the stack.
Thanks, id love to hear a 'short story' on a few images of various
colorspaces passing through QC, and how it is converted etc. Might
make a fun exercise.
That would be interesting for me also, I'll ask around here to see if
anyone can provide that.
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