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使用 drawInRect 绘图时丢失清晰度解决方法
source link: http://dijkst.github.io/blog/2013/07/24/shi-yong-drawinrect-hui-tu-shi-diu-shi-qing-xi-du-jie-jue-fang-fa/
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使用 drawInRect 绘图时丢失清晰度解决方法
2013/07/24 18:40 | Comments
有一个小需求，就是需要动态修改一张图片上面的数字，当然不能事先准备那么多数字的图片，所以就需要动态的在一个图片上面画数字。
需求很简单，我首先这么实现：
UIImage *image = [UIImage imageNamed:@"assemble-a"];
UIGraphicsBeginImageContext(image.size);
[image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
画出来的图怎么看都模糊，刚开始没在意，以为就是这样的……
然后给美女设计师看效果，直接回了一句——怎么这么糊……
额，好像确实是越看越糊……
既然是模糊了，极有可能是 scale 没有对。凡事先问 Google，还真有同样的问题的：
drawInRect: losing Quality of Image resolution
解决方法就是用
UIGraphicsBeginImageContextWithOptions(image.size, NO, [[UIScreen mainScreen] scale]);
UIGraphicsBeginImageContext(image.size);
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