http://developer.apple.com/mac/library/qa/qa2007/qa1509.html
やはり、CGBitmapContextGetDataで、CoreGraphics のコンテキストの、ビットマップイメージへのポインタを、得るみたいですね。(^^;;
void ManipulateImagePixelData(CGImageRef inImage) { // Create the bitmap context CGContextRef cgctx = CreateARGBBitmapContext(inImage); if (cgctx == NULL) { // error creating context return; } // Get image width, height. We'll use the entire image. size_t w = CGImageGetWidth(inImage); size_t h = CGImageGetHeight(inImage); CGRect rect = {{0,0},{w,h}}; // Draw the image to the bitmap context. Once we draw, the memory // allocated for the context for rendering will then contain the // raw image data in the specified color space. CGContextDrawImage(cgctx, rect, inImage); // Now we can get a pointer to the image data associated with the bitmap // context. void *data = CGBitmapContextGetData (cgctx); if (data != NULL) { // **** You have a pointer to the image data **** // **** Do stuff with the data here **** } // When finished, release the context CGContextRelease(cgctx); // Free image data memory for the context if (data) { free(data); } }