iOS中一行代码实现 UIView 镂空效果

 2、将

UIImage 转换为只有 alpha 通道的 CGContextRef

CGImageRef originalMaskImage = [image CGImage];
float width = CGImageGetWidth(originalMaskImage);
float height = CGImageGetHeight(originalMaskImage);
  
int strideLength = ROUND_UP(width * 1, 4);
unsigned char * alphaData = calloc(strideLength * height, sizeof(unsigned char));
CGContextRef alphaOnlyContext = CGBitmapContextCreate(alphaData,
                           width,
                           height,
                           8,
                           strideLength,
                           NULL,
                           kCGImageAlphaOnly);
  
CGContextDrawImage(alphaOnlyContext, CGRectMake(0, 0, width, height), originalMaskImage);
								 
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