ios - 如何更改具有透明区域的UIIMAGE的色调？

Question

我目前正在使用以下代码来更改色调:

  CGSize imageSize = [imageView.image size];
  CGRect imageExtent = CGRectMake(0,0,imageSize.width,imageSize.height);

  // Create a context containing the image.
  UIGraphicsBeginImageContext(imageSize);
  CGContextRef context = UIGraphicsGetCurrentContext();
  [imageView.image drawAtPoint:CGPointMake(0, 0)];

  // Draw the hue on top of the image.
  CGContextSetBlendMode(context, kCGBlendModeHue);
  [color set];

  UIBezierPath *imagePath = [UIBezierPath bezierPathWithRect:imageExtent];
  [imagePath fill];

  // Retrieve the new image.
  UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
  imageView.image= result;

  UIGraphicsEndImageContext();

这段代码工作正常，唯一的问题是它还设置了透明部分的颜色。我可以避免将色调应用于 UIImage 的透明区域吗？

附上两张图片供引用:

提前致谢？

输出

Answer 1

在添加颜色之前从图像应用 mask 。

CGSize imageSize = [imageView.image size];
CGRect imageExtent = CGRectMake(0,0,imageSize.width,imageSize.height);

// Create a context containing the image.
UIGraphicsBeginImageContext(imageSize);
CGContextRef context = UIGraphicsGetCurrentContext();
[imageView.image drawAtPoint:CGPointMake(0, 0)];

// Setup a clip region using the image
CGContextSaveGState(context);
CGContextClipToMask(context, imageExtent, imageView.image.CGImage);

[color set];
CGContextFillRect(context, imageExtent);

// Draw the hue on top of the image.
CGContextSetBlendMode(context, kCGBlendModeHue);
[color set];

UIBezierPath *imagePath = [UIBezierPath bezierPathWithRect:imageExtent];
[imagePath fill];

CGContextRestoreGState(context); // remove clip region

// Retrieve the new image.
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
imageView.image= result;

UIGraphicsEndImageContext();