NSTextAttachment绑定NSAttributedString后图片垂直翻转问题求助

这个问题我之前也碰到过！根源在于macOS里NSImage和文本布局的坐标系不匹配：NSImage的原点在左下角，而NSTextAttachment渲染时用的是类似UIKit的坐标系（原点在左上角），直接绑定图片就会出现垂直翻转的情况。

给你几个实用的解决办法：

方法一：调整NSTextAttachment的bounds偏移 #

最简单的方式，不需要修改图片本身，直接通过调整bounds的y值来修正位置：

NSTextAttachment *attachment = [[NSTextAttachment alloc] init]; 
NSImage *image = [NSImage imageNamed:@"emotion"];
// 将图片向上偏移自身高度，抵消坐标系差异
attachment.bounds = CGRectMake(0, -image.size.height, image.size.width, image.size.height);
attachment.image = image; 
NSAttributedString *attributedString = [NSAttributedString attributedStringWithAttachment: attachment]; 
[[_feedbackContent textStorage] appendAttributedString:attributedString];

方法二：创建翻转后的NSImage实例 #

如果需要保留原始图片，或者要复用翻转后的图片，可以手动绘制一个翻转版本：

NSImage *originalImage = [NSImage imageNamed:@"emotion"];
NSImage *flippedImage = [[NSImage alloc] initWithSize:originalImage.size];

[flippedImage lockFocus];
// 创建翻转变换
NSAffineTransform *flipTransform = [NSAffineTransform transform];
[flipTransform scaleXBy:1.0 yBy:-1.0];
[flipTransform translateXBy:0.0 yBy:-originalImage.size.height];
[flipTransform concat];

// 绘制原始图片到新图片中
[originalImage drawAtPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositingOperationCopy fraction:1.0];
[flippedImage unlockFocus];

// 绑定到NSTextAttachment
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
attachment.image = flippedImage;
NSAttributedString *attributedString = [NSAttributedString attributedStringWithAttachment:attachment];
[[_feedbackContent textStorage] appendAttributedString:attributedString];

方法三：利用NSImage的快捷翻转方法 #

NSImage自带flippedImage方法可以直接获取垂直翻转后的图片，不过部分场景下可能需要配合bounds微调，保险起见还是推荐前两种方法：

NSTextAttachment *attachment = [[NSTextAttachment alloc] init]; 
NSImage *image = [[NSImage imageNamed:@"emotion"] flippedImage];
attachment.image = image; 
NSAttributedString *attributedString = [NSAttributedString attributedStringWithAttachment: attachment]; 
[[_feedbackContent textStorage] appendAttributedString:attributedString];

选哪种看你的需求，方法一最快捷，方法二更灵活可控~

内容的提问来源于stack exchange，提问作者jimwan