我正在使用用户使用UIBezierPath选择其中一部分的图像.如何删除/清除/清除不是该选择的一部分的所有内容？
解决方法
有一条路很容易.只需将路径设置为剪切路径：
- (UIImage *)maskImage:(UIImage *)originalImage toPath:(UIBezierPath *)path {
UIGraphicsBeginImageContextWithOptions(originalImage.size,NO,0);
[path addClip];
[originalImage drawAtPoint:CGPointZero];
UIImage *maskedImage = UIGraphicsGetimageFromCurrentimageContext();
UIGraphicsEndImageContext();
return maskedImage;
}
如果要使用多个路径的并集,则更难,因为Quartz没有任何直接计算两个路径的并集的函数.一种方法是将每个路径逐个填入蒙版,然后通过掩码绘制图像：
- (UIImage *)maskedImage
{
CGRect rect = CGRectZero;
rect.size = self.originalImage.size;
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0); {
[[UIColor blackColor] setFill];
UIRectFill(rect);
[[UIColor whiteColor] setFill];
for (UIBezierPath *path in self.paths)
[path fill];
}
UIImage *mask = UIGraphicsGetimageFromCurrentimageContext();
UIGraphicsEndImageContext();
UIGraphicsBeginImageContextWithOptions(rect.size,0.0); {
CGContextClipToMask(UIGraphicsGetCurrentContext(),rect,mask.CGImage);
[self.originalImage drawAtPoint:CGPointZero];
}
UIImage *maskedImage = UIGraphicsGetimageFromCurrentimageContext();
UIGraphicsEndImageContext();
return maskedImage;
}