如何在iOS中将正方形图像蒙版成带有圆角的图像?

问题描述

如何将方形图像蒙版成带有圆角的图像?

How can you mask a square image into an image with round corners?

推荐答案

您可以使用CoreGraphics使用以下代码段为圆形矩形创建路径:

You can use CoreGraphics to create a path for a round rectangle with this code snippet:

static void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth, float ovalHeight)
{
    float fw, fh;
    if (ovalWidth == 0 || ovalHeight == 0) {
        CGContextAddRect(context, rect);
        return;
    }
    CGContextSaveGState(context);
    CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
    CGContextScaleCTM (context, ovalWidth, ovalHeight);
    fw = CGRectGetWidth (rect) / ovalWidth;
    fh = CGRectGetHeight (rect) / ovalHeight;
    CGContextMoveToPoint(context, fw, fh/2);
    CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1);
    CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1);
    CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1);
    CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1);
    CGContextClosePath(context);
    CGContextRestoreGState(context);
}

然后调用CGContextClip(context);将其剪切到矩形路径.现在，完成的所有绘制(包括绘制图像)都将被裁剪为圆形矩形.

And then call CGContextClip(context); to clip it to the rectangle path. Now any drawing done, including drawing an image, will be clipped to the round rectangle shape.

作为示例，假设图像"是UIImage，并且位于drawRect:方法中:

As an example, assuming "image" is a UIImage, and this is in a drawRect: method:

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
addRoundedRectToPath(context, self.frame, 10, 10);
CGContextClip(context);
[image drawInRect:self.frame];
CGContextRestoreGState(context);

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