如何改变具有透明区域的UIIMAGE的色调？

我目前正在使用以下代码进行色调更改：

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到UIImage的透明区域吗？

附上两张图片供参考：

提前致谢？

产量

Answer 1

在添加颜色之前应用图像中的蒙版。

 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(); 

Answer 2

我使用Core Image来完成你想要实现的目标。 注意：这是在Swift中，但你应该得到要点。

  var hueFilter = CIFilter(name: "CIHueAdjust", withInputParameters: ["inputAngle" : M_2_PI]) let imageRef = UIImage(named: "Maggie").CGImage let coreImage = CIImage(CGImage: imageRef) hueFilter.setValue(coreImage, forKey: kCIInputImageKey) maggieView.image = UIImage(CIImage: hueFilter.outputImage) 

一个注意事项：inputAngle根据此 SOpost以弧度完成。

Answer 3

这段代码对我有用。

 - (UIImage*)imageWithImage:(UIImageView*)source colorValue:(CGFloat)hue { CGSize imageSize = [source.image size]; CGRect imageExtent = CGRectMake(0,0,imageSize.width,imageSize.height); // Create a context containing the image. UIGraphicsBeginImageContext(imageSize); CGContextRef context = UIGraphicsGetCurrentContext(); [source.image drawAtPoint:CGPointMake(0, 0)]; // Setup a clip region using the image CGContextSaveGState(context); CGContextClipToMask(context, source.bounds, source.image.CGImage); self.imageColor = [UIColor colorWithHue:hue saturation:1.0 brightness:1 alpha:1.0]; [self.imageColor set]; CGContextFillRect(context, source.bounds); // Draw the hue on top of the image. CGContextSetBlendMode(context, kCGBlendModeHue); [self.imageColor set]; UIBezierPath *imagePath = [UIBezierPath bezierPathWithRect:imageExtent]; [imagePath fill]; CGContextRestoreGState(context); // remove clip region // Retrieve the new image. UIImage *result = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return result; }