在iOS Cocoa中叠加非透明像素

问题描述

iOS SDK上有没有办法用彩色像素覆盖图像中的非透明像素？

Is there any way on the iOS SDK to overlay the non-transparent pixels in an image with colored pixels?

非常感谢两位回答。

我实现的最终解决方案使用了在子类UIView的drawRect方法中接受的答案中提到的代码，我使用了以下内容覆盖颜色的代码：

The final solution I implemented used the code mentioned in the accepted answer within the drawRect method of a subclassed UIView, I used the following code to overlay the color:

CGContextSetFillColor(context, CGColorGetComponents([UIColor colorWithRed:0.5 green:0.5 blue:0 alpha:1].CGColor));

CGContextFillRect(context, area);

推荐答案

我想你可能正在寻找混合模式 kCGBlendModeSourceAtop 即可。首先，将UIImage绘制到您的视图中。然后使用

I think you are probably looking for the blend mode kCGBlendModeSourceAtop. First, draw the UIImage into your view. Then obtain the current graphics context with

CGContext currentCtx = UIGraphicsGetCurrentContext();

然后保存上下文状态，并设置混合模式：

Then save the context state, and set the blend mode:

CGContextSaveGState(currentCtx);
CGContextSetBlendMode(currentCtx, kCGBlendModeSourceAtop);

然后你可以在UIImage的不透明像素上绘制任何想要覆盖的内容。之后，只需重置上下文状态：

Then you can draw whatever you want to be overlaid over the opaque pixels of the UIImage. Afterward, just reset the context state:

CGContextRestoreGState(currentCtx);

希望这有帮助！

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