Core Image should not clamp any values: the kernel patch creates a
CIImage which is a "recipe" on how one of more input images must be
transformed. Thus the range of output values does not matter at this
point (can be negative or over 1.).
The clamping would occur only at the time or rendering of the image,
if you render it in a context whose pixel format does not support out
of range pixel value, as it is the case in QC (for instance, RGBA8).
Only the destination pixels are affected though: in the case of
successive kernel patches, intermediary values would not be clamped.
If you want to change the destination pixel format to avoid all
clamping, you can embed your composition in a custom cocoa app and
create a QCRenderer with an openGL context you created on your own.
Make sure in that case that in your composition, the CIImage is drawn
on a billboard patch with "Direct CI Rendering" checked.
Kevin
On Feb 8, 2007, at 6:28 AM, Oliver Donald wrote:
Hi,
Sorry if this is the wrong list, but I can't see one for Apple's
CoreImage kernel language...
I've written a CIKernel in QC that does some physics calculations and
I'm storing the simulation's physical attributes in the different
colour
components. However, some of these values may need to go negative -
what
happens to the output image if some of the pixels contain negative
values in the ARGB components, or the component values go above
1.0? Are
the component values clipped only when the image is rendered, or does
the clipping happen on write?
Thanks,
oli
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