iPhone以编程方式裁剪方形图像以显示为圆形 [英] iPhone programmatically crop a square image to appear as circle

问题描述

我正在尝试使用iPhone上相机胶卷中的图像为自定义样式UIButton创建图像。该按钮具有圆形背景，实际上显示为圆形。现在我需要一个图像进入按钮的中间，该图像也显示为圆形。

I'm trying to create an image for a custom style UIButton using an image from the camera roll on iPhone. The button has a circular background and effectively appears as a circle. Now I need an image to go in the middle of the button that also appears round.

如何将方形UII图像切割成圆形区域以外的透明度？

How do I cut a square UIImage to appear round with transparency outside of the round area?

如果屏蔽涉及到，我需要预先渲染一个面具，还是可以通过编程方式创建一个（例如：圆圈）？

If masking is involved, do I need to pre-render a mask or can I create one programmatically(ex: a circle)?

谢谢！

推荐答案

是的，您可以使用 CoreGraphics 动态绘制遮罩。
然后你可以创建蒙面图像。

Yes you can use CoreGraphics to draw the mask dynamically. Then you can create the masked image.

蒙版示例：

- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage
{
  CGImageRef maskRef = maskImage.CGImage;
  CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                      CGImageGetHeight(maskRef),
                                      CGImageGetBitsPerComponent(maskRef),
                                      CGImageGetBitsPerPixel(maskRef),
                                      CGImageGetBytesPerRow(maskRef),
                                      CGImageGetDataProvider(maskRef), NULL, false);

  CGImageRef maskedImageRef = CGImageCreateWithMask([image CGImage], mask);
  UIImage *maskedImage = [UIImage imageWithCGImage:maskedImageRef];
  CGImageRelease(maskedImageRef);
  CGImageRelease(mask);
  return maskedImage;
}

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