如何倾斜 UIImage 的下部答案

【问题标题】：How do I skew the lower section of a UIImage如何倾斜 UIImage 的下部
【发布时间】：2011-11-29 17:33:55
【问题描述】：

我想像这样倾斜 UIImage 的下部：

最好的方法是什么？

【问题讨论】：

我收到的一个建议是将图像分成两部分，倾斜其中一个，然后重新组合。

【解决方案1】：

这是我想出的解决方案。它将图像一分为二，然后剪切底部的一个：

CGFloat foldHeightInPercent = 0.9f;
CGFloat totalHeight = 39;
CGRect topImageRect = CGRectMake(0, 0, 50, totalHeight * foldHeightInPercent);

//top image
CGFloat scale = [[UIScreen mainScreen] scale];
CGRect topCropRect = CGRectMake(0, 0, image.size.width * scale, image.size.height * foldHeightInPercent * scale);
CGImageRef topImageRef = CGImageCreateWithImageInRect(image.CGImage, topCropRect);
UIImageView *topImageView = [[UIImageView alloc] initWithFrame:topImageRect];
[topImageView setImage:[UIImage imageWithCGImage:topImageRef]];
CGImageRelease(topImageRef);    
[self.view addSubview:topImageView];

//bottom image
CGRect bottomImageRect = CGRectMake(1, totalHeight * foldHeightInPercent, 50, totalHeight * (1.0f - foldHeightInPercent));
CGFloat yPos = image.size.height * foldHeightInPercent * scale;
CGRect bottomCropRect = CGRectMake(0, yPos, image.size.width * scale, image.size.height * (1.0f - foldHeightInPercent) * scale);
CGImageRef bottomImageRef = CGImageCreateWithImageInRect(image.CGImage, bottomCropRect);
UIImageView *bottomImageView = [[UIImageView alloc] initWithFrame:bottomImageRect];
[bottomImageView setImage:[UIImage imageWithCGImage:bottomImageRef]];
CGImageRelease(bottomImageRef);  

CGFloat skewAngle = 20.0f;
CGFloat skew = tan(skewAngle * M_PI / 180.f);
CGAffineTransform t = CGAffineTransformMake(1.0, 0.0, skew, 1.0, 0.0, 0.0);
bottomImageView.transform = t;
[self.view addSubview:bottomImageView];

【讨论】：