点击时如何像UIButton一样在UIImage上实现突出显示? [英] How to implement highlighting on UIImage like UIButton does when tapped?

问题描述

我需要在点按时突出显示UIButton在图像上的效果.参见:

I need to replicate the effect that the UIButton does on an image when tapped, the highlighting. See:

原始PNG是带有alpha背景的正方形.当我将其设置为UIButton的图像时，它会自动在图像的非alpha像素上应用效果.

The original PNG is a square with alpha background. When I set it as UIButton's image it automatically apply an effect on the non-alpha pixels of the image.

如何实现这种效果?

推荐答案

您可以在UIImage上使用简单的类别来实现此目标:

You could achieve this with a simple category on UIImage:

@interface UIImage (Tint)

- (UIImage *)tintedImageUsingColor:(UIColor *)tintColor;

@end

@implementation UIImage (Tint)

- (UIImage *)tintedImageUsingColor:(UIColor *)tintColor {
  UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
  CGRect drawRect = CGRectMake(0, 0, self.size.width, self.size.height);
  [self drawInRect:drawRect];
  [tintColor set];
  UIRectFillUsingBlendMode(drawRect, kCGBlendModeSourceAtop);
  UIImage *tintedImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return tintedImage;
}

@end

对于上面显示的效果，您将传递[UIColor colorWithWhite:0.0 alpha:0.3]之类的内容作为tintColor参数(带有alpha值的实验).

For the effect shown above, you'd pass something like [UIColor colorWithWhite:0.0 alpha:0.3] as the tintColor parameter (experiment with the alpha value).

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