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Re: Color values from a CGImage

Thanks for the response, I'll elaborate a bit on what I'm trying to do:

I have to images that I run through a CIFilter (CIDifferenceBlendMode), the result of this filter goes through another filter (CIAreaAverage), which returns a single pixel image that represents the average color value of the difference blend. If the result is a black pixel, the images were the same. Anything other then black means there was a difference. I want to measure the RGB values of the result of th average filter so I can assess how much difference there was, so I'm looking for a way to represent the RGB values in numbers.

MB

On 1 mrt 2008, at 00:45, Scott Thompson wrote:


On Feb 29, 2008, at 4:30 PM, Marcel Borsten wrote:

Hi all,

Is there an easy way to get the color values (RGB or RGBA) out of a pixel from a CGImage?

In general, no, because a CGImage doesn't contain pixels. :-)

To do what you are trying to do, however, you need to create a CGBItmapContext in the color space of your choice and draw the image into that context.  You can then read the value of the bitmap context's pixels from the memory that you supply when you create it.

Scott



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