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

问题描述

有没有办法消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 topic 上找到了这个示例代码，但我不明白它是如何工作的

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();
}

也许我走错路了.

Maybe I'm in the wrong way.

问候，
kl94

Regards,
kl94

推荐答案

代码使用quartz(iPhone的图形引擎)来裁剪图像.一些细节:

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

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

您首先需要某种目标"来绘制.在图形中，这通常称为上下文.上面，你告诉系统需要一个给定大小的(位图)图像上下文，然后你得到一个对它的引用.

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，然后剪辑上下文.也就是只在这些区域画图".

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];

您在新的上下文中绘制图像.只有被剪裁的区域会被绘制，所以其余的被有效地擦除.

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，您只需要求系统将在您上面设置的上下文(目标)中绘制的图像返回给您

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，您可能需要查看每个函数的参考以获取更多详细信息.

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

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