如何在iPhone SDK中将正方形图像蒙上圆角图像？ [英] How to mask a square image into an image with round corners in the iPhone SDK?

问题描述

你如何将一个正方形图像掩盖成一个带有圆角的图像？你可以使用CoreGraphics创建一个路径对于这个代码片段的圆形矩形：

  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，任何完成的绘图（包括绘制图像）都将被裁剪成圆形的矩形形状。

例如，假设image是UIImage，并且这是一个drawRect：方法：

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

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

解决方案

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);
}

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.

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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