Gradient Alpha Mask in iOS
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
NSArray *colors = [NSArray arrayWithObjects:
(id)[[UIColor colorWithWhite:0 alpha:0] CGColor],
(id)[[UIColor colorWithWhite:0 alpha:1] CGColor],
nil];
[gradientLayer setColors:colors];
[gradientLayer setStartPoint:CGPointMake(0.0f, 1.0f)];
[gradientLayer setEndPoint:CGPointMake(0.0f, 0.6f)];
gradientLayer.frame = uiimageview.bounds;
gradientLayer.layer.mask = gradientLayer;
Gradient View
UIImageView *uiimageview = (UIImageView *)[self viewWithTag:100];
if ([[uiimageview.layer sublayers] count] < 1) {
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
NSArray *colors = [NSArray arrayWithObjects:
(id)[[UIColor colorWithWhite:0 alpha:0.9] CGColor],
(id)[[UIColor colorWithWhite:0 alpha:0.1] CGColor],
nil];
[gradientLayer setColors:colors];
[gradientLayer setStartPoint:CGPointMake(0.0f, 1.0f)];
[gradientLayer setEndPoint:CGPointMake(0.0f, 0.2f)];
gradientLayer.frame = uiimageview.bounds;
[uiimageview.layer insertSublayer:gradientLayer atIndex:0];
}