使用alpha值混合UIImage

Question

如何通过仅更改一个图像的alfa来混合两个图像，以便上面的图像稍微透明，并且上图将在背景图上绘制时显示。

Answer 1

你可以做到这一点通过ImageView的alpha属性

imageView.alpha = 0.0f; 

详细代码：

UIImage *bottomImage = [UIImage imageNamed:@"bottomImage.png"]; 
    UIImage *topImage = [UIImage imageNamed:@"topImage.png"]; 

    CGSize newSize = CGSizeMake(width, height); 
    UIGraphicsBeginImageContext(newSize); 

    // Use existing opacity as is 
    [bottomImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)]; 
    // Apply supplied opacity 
    [topImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeNormal alpha:0.8]; 

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 

    UIGraphicsEndImageContext(); 

看到更多细节的here