Change the Colors of a UIImage Using a UIColor

Lots of googling led me here. Then it was pretty easy to mash this into that. When you combine this with the UIButton images provided by Apple, you can do cool stuff.

- (UIImage *) changeColorForImage:(UIImage *)image toColor:(UIColor*)color {

UIGraphicsBeginImageContext(image.size);

CGRect contextRect;

contextRect.origin.x = 0.0f;

contextRect.origin.y = 0.0f;

contextRect.size = [image size];

// Retrieve source image and begin image context

CGSize itemImageSize = [image size];

CGPoint itemImagePosition; 

itemImagePosition.x = ceilf((contextRect.size.width - itemImageSize.width) / 2);

itemImagePosition.y = ceilf((contextRect.size.height - itemImageSize.height) );

UIGraphicsBeginImageContext(contextRect.size);

CGContextRef c = UIGraphicsGetCurrentContext();

// Setup shadow

// Setup transparency layer and clip to mask

CGContextBeginTransparencyLayer(c, NULL);

CGContextScaleCTM(c, 1.0, -1.0);

CGContextClipToMask(c, CGRectMake(itemImagePosition.x, -itemImagePosition.y, itemImageSize.width, -itemImageSize.height), [image CGImage]);

// Fill and end the transparency layer

const float* colors = CGColorGetComponents( color.CGColor );

CGContextSetRGBFillColor(c, colors[0], colors[1], colors[2], .75);

contextRect.size.height = -contextRect.size.height;

contextRect.size.height -= 15;

CGContextFillRect(c, contextRect);

CGContextEndTransparencyLayer(c);

UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return img;

}

Now that I know this simple code, I can even create idiotic methods like:

- (UIColor*) oppositeColor:(UIColor*)color {

const float* colors = CGColorGetComponents(color.CGColor);

return [UIColor colorWithRed:1-colors[0] green:1-colors[1] blue:1-colors[2] alpha:1];

}