使用alpha值混合UIImage

Question

如何通過僅更改一個圖像的alfa來混合兩個圖像，以便上面的圖像稍微透明，並且上圖將在背景圖上繪製時顯示。

Answer 1

你可以做到這一點通過ImageView的alpha屬性

imageView.alpha = 0.0f; 

詳細代碼：

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(); 

看到更多細節的here