iPhone 结构位图的函数

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// Courtesy of Apple, Create Bitmap with Alpha/RGB valuesCGContextRef CreateARGBBitmapContext (CGImageRef inImage, CGSize size){    CGContextRef    context = NULL;    CGColorSpaceRef colorSpace;    void *          bitmapData;    int             bitmapByteCount;    int             bitmapBytesPerRow;	    size_t pixelsWide = size.width;    size_t pixelsHigh = size.height;    bitmapBytesPerRow   = (pixelsWide * 4); //ARGB    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);    colorSpace = CGColorSpaceCreateDeviceRGB();		if (colorSpace == NULL)    {        fprintf(stderr, "Error allocating color space\n");        return NULL;    }	    // allocate the bitmap & create context    bitmapData = malloc( bitmapByteCount );    if (bitmapData == NULL)    {        fprintf (stderr, "Memory not allocated!");        CGColorSpaceRelease( colorSpace );        return NULL;    }	    context = CGBitmapContextCreate (bitmapData, pixelsWide, pixelsHigh, 8,									 bitmapBytesPerRow, colorSpace,									 kCGImageAlphaPremultipliedFirst);    if (context == NULL)    {        free (bitmapData);        fprintf (stderr, "Context not created!");    }	    CGColorSpaceRelease( colorSpace );    return context;}// Return a C-based bitmap of the image data inside an imageunsigned char *RequestImagePixelData(UIImage *inImage){	CGImageRef img = [inImage CGImage];	CGSize size = [inImage size];    	CGContextRef cgctx = CreateARGBBitmapContext(img, size);    if (cgctx == NULL) return NULL;	    CGRect rect = {{0,0},{size.width, size.height}};    CGContextDrawImage(cgctx, rect, img);	unsigned char *data = CGBitmapContextGetData (cgctx);	CGContextRelease(cgctx);		return data;}

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使用位图某像素:

[UIColor?

colorWithRed: (float) (bitmap[startByte+1]/255.0f)

green: (float) (bitmap[startByte+2]/255.0f)

blue:? (float) (bitmap[startByte+3]/255.0f)

alpha: (float)(bitmap[startByte]]