如何擦除UIImage的一部分 [英] How erase part of UIImage

问题描述

有没有方法可以删除该图像的黑色背景

Is there a way to erase the black background for that image

我在这个主题上找到了这个示例代码，但我没有了解它是如何工作的

I've found this sample code found on this topic but i don't understand how it works

- (void)clipImage {
  UIImage *img = imgView.image;
  CGSize s = img.size;
  UIGraphicsBeginImageContext(s);
  CGContextRef g = UIGraphicsGetCurrentContext();
  CGContextAddPath(g,erasePath);
  CGContextAddRect(g,CGRectMake(0,0,s.width,s.height));
  CGContextEOClip(g);
  [img drawAtPoint:CGPointZero];
  imageView.image = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
}

也许我的方式错了。

Maybe I'm in the wrong way.

问候，

kl94

Regards,
kl94

推荐答案

代码正在使用石英（iPhone的图形引擎）剪辑图像。一些细节：

The code is using quartz (iPhone's graphics engine) to clip the image. some details:

UIGraphicsBeginImageContext(s);
CGContextRef g = UIGraphicsGetCurrentContext();

首先需要某种目标来绘制。在图形中，通常称为上下文。在上面，你告诉系统需要给定大小的（位图）图像上下文然后你得到它的引用。

You first need some sort of "target" to draw to. In graphics, that's usually called a context. Above, you tell the system a (bitmap) image context with given size is needed and then you get a reference to it.

CGContextAddPath(g,erasePath);
CGContextAddRect(g,CGRectMake(0,0,s.width,s.height));
CGContextEOClip(g);

在这里，您提供上下文的路径，然后剪切上下文。这就是说只在这些地区画画。

Here, you provide a path to the context, and then clip the context. That's to say "only draw in these regions."

[img drawAtPoint:CGPointZero];

您可以在新的上下文中绘制图像。只会绘制剪切区域，因此其余区域将被有效删除。

You draw the image in the new context. Only the clipped region will be drawn, so the rest is effectively erased.

imageView.image = UIGraphicsGetImageFromCurrentImageContext();

现在，您只需要让系统返回上下文中绘制的图像（目标）你在上面设置

Now here, you just ask the system to give you back the image drawn in the context (target) you set up above

注意：这是一个粗略的描述，你可能想看看每个函数的参考以获得更多细节。

Note: this is a rough description, you might wanna look at the reference for each function to get more details.

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