I searched everywhere but didn't find the solution. I have image 1. How can I programatically tint them with gradient to get images 2 and 3? Here are those images:
Tints that I applied to them via Photoshop are simple 2-color linear gradients.
And my question is: how can I achieve this effect programatically?
Solution: jrtc27 gave me almost working example. I fixed it (for ARC) and made it reusable (using UIImage's category). Here is it:
- (UIImage *)tintedWithLinearGradientColors:(NSArray *)colorsArr {
CGFloat scale = self.scale;
UIGraphicsBeginImageContext(CGSizeMake(self.size.width * scale, self.size.height * scale));
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0, self.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetBlendMode(context, kCGBlendModeNormal);
CGRect rect = CGRectMake(0, 0, self.size.width * scale, self.size.height * scale);
CGContextDrawImage(context, rect, self.CGImage);
// Create gradient
UIColor *colorOne = [colorsArr objectAtIndex:1]; // top color
UIColor *colorTwo = [colorsArr objectAtIndex:0]; // bottom color
NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, (id)colorTwo.CGColor, nil];
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColors(space, (__bridge CFArrayRef)colors, NULL);
// Apply gradient
CGContextClipToMask(context, rect, self.CGImage);
CGContextDrawLinearGradient(context, gradient, CGPointMake(0,0), CGPointMake(0,self.size.height * scale), 0);
UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return gradientImage;
}
EDIT: Here is a version which supports non-retina and retina displays
The method can be used as a category for UIImage
+ (UIImage *)imageWithGradient:(UIImage *)img startColor:(UIColor *)color1 endColor:(UIColor *)color2 {
UIGraphicsBeginImageContextWithOptions(img.size, NO, img.scale);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0, img.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetBlendMode(context, kCGBlendModeNormal);
CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
//CGContextDrawImage(context, rect, img.CGImage);
// Create gradient
NSArray *colors = [NSArray arrayWithObjects:(id)color2.CGColor, (id)color1.CGColor, nil];
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColors(space, (__bridge CFArrayRef)colors, NULL);
// Apply gradient
CGContextClipToMask(context, rect, img.CGImage);
CGContextDrawLinearGradient(context, gradient, CGPointMake(0,0), CGPointMake(0, img.size.height), 0);
UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGGradientRelease(gradient);
CGColorSpaceRelease(space);
return gradientImage;
}
Edit: added change by sobri