How to implement alpha gradient on a image?

Question

I want to implement alpha gradient on an image. From 0.5 alfa on top of the image to 0.0 on bottom. Any advice, tutorial, link is welcome.

Answer 1

You can try CAGradientLayer.

UIView *view = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 100)] autorelease];
 CAGradientLayer *gradient = [CAGradientLayer layer];
 gradient.frame = view.bounds;
 gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor blackColor] CGColor], (id)[[UIColor whiteColor] CGColor], nil];
 [view.layer insertSublayer:gradient atIndex:0];

Another option

Try the answer suggested by @Caleb in this previous SO question

You can go for Graphics Contexts. All drawing happens in a graphics context. If you want to create an image that has a radial gradient, or a linear gradient, or anything else, you'll need to:

• Create a graphics context for your image with
  UIGraphicsBeginImageContextWithOptions.
• Do whatever drawing you want to appear in the image.
• Call UIGraphicsGetImageFromCurrentImageContext to get the image from the context.
  This gives you a UIImage, so no need to convert from a CGImage.
• Call UIGraphicsEndImageContext to clean up the context.

You can also have a look at Radial gradient on UImage