Le 3 mai 08 à 20:06, Josh Burnett a écrit :
In a photography app, I'm chaining a series of CIFilters together to
process the image. I'm able to do the chain just fine, but I'm only
using a few filters at the moment. As I increase the length of this
chain, am I going to run into performance issues? Here's my code:
exposureFilter = [CIFilter filterWithName: @"CIExposureAdjust"
keysAndValues:
@"inputImage", inputImage,
@"inputEV", [NSNumber numberWithFloat: exposureValue],
nil];
outputImage = [exposureFilter valueForKey: @"outputImage"];
[exposureFilter retain];
zoomFilter = [CIFilter filterWithName: @"CILanczosScaleTransform"
keysAndValues:
@"inputImage", outputImage,
@"inputScale", [NSNumber numberWithFloat: mappedZoom],
@"inputAspectRatio", [NSNumber numberWithFloat: 1.0],
nil];
outputImage = [zoomFilter valueForKey: @"outputImage"];
[zoomFilter retain];
Obviously, it's easy to continue to add to this chain. Is this the
most efficient way to string multiple filters together? I can
probably use Quartz Composer to create a single image unit that does
all of the processing. Would that be any more efficient, or would
it be essentially the same result?
Thanks,
Josh
On Mac OS 10.5, there is a class designed to create and store filter
chain (CIFilterGenerator). You may have a look at it.
You also have to know that the filter is not computed when you call
[valueForKey:@"outputImage"] but when you try to access the final
outputImage content (to display it for example). Even if this is not
obvious as you have to create a new image instance for each filter,
Core Image optimize the image processing. So creating a single image
unit would probably not be more efficient.
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