Re: QCRenderer and colorspace parameterizing

[Raphael Sebbe @ Google]

Well back in the Tiger days, this was the only way to get a QuickTime  
to render the same colors as in QuickTime Player through CIContexts. I  
don't know whether this is still needed in Leopard, I will check that.  
I'd be happy to use default values everywhere if possible.

Thanks for the info,

Raphael

On 04 Dec 2007, at 22:15, Pierre-Olivier Latour wrote:

You are forcing the CIContext to process images in GenericRGB  
colorspace instead of the default LinearRGB colorspace, which is not  
recommended and is likely to give incorrect results. You should  
leave kCIContextWorkingColorSpace to its default unless you have a  
very good reason for it.

CIContexts used by QC always use the LinearRGB as the processing  
colorspace.

On Dec 4, 2007, at 1:08 PM, Raphael Sebbe @ Google wrote:

Hi,

I have a few different pipelines rendering images, some QC-based,  
some OpenGL/CI-based, some Quartz/CI-based. All have colorspaces  
associated.

The QC-based renderings has a slightly different color output. I  
think this is because my CI-based contexts have this setup, which  
sems not possible to create through QCRenderer:

CGColorSpaceRef colorSpace =  
CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                         
(id)colorSpace,kCIContextOutputColorSpace,
                                         
(id)colorSpace,kCIContextWorkingColorSpace,
                                         nil];
		_hiresImageContext = [CIContext  
contextWithCGContext:_hiresGraphicsContext options:options];


The rendering are the same if options is set to nil in the CI-based  
contexts. QCRenderer is created with this code:

CGColorSpaceRef colorSpace =  
CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
	id path = [[NSBundle mainBundle] pathForResource:@"HYTheater"  
ofType:@"qtz" inDirectory:nil];
        id composition = [QCComposition compositionWithFile:path];
	_qcTheater = [[QCRenderer alloc] initWithCGLContext: 
[_openGLContext CGLContextObj] pixelFormat:[_openGLPixelFormat  
CGLPixelFormatObj] colorSpace:colorSpace composition:composition];

Any advice to setup the QCRenderer to render the same as CIContexts ?

Thanks,

Raphael
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Technologist - Apple, Inc.




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