UIGraphicsGetImageFromCurrentImageContext给出质量差/低分辨率图像，我如何得到更好？ [英] UIGraphicsGetImageFromCurrentImageContext gives poor quality / low resolution image, how do I get better?

问题描述

好的，所以我正在拍摄的照片，我用我的相机在iPhone上拍摄的屏幕截图。我把相机照片放到UIImageView，并抓住它的屏幕截图使用这种代码（这是从 http://www.skylarcantu.com/blog/2009/10/16/saving-a-view-as-an-image/ ） ...

Ok so I am taking a screen shot of a photo I took with my camera on the iPhone. I put the camera photo into UIImageView and grab a screenshot of it using this sort of code (this is from http://www.skylarcantu.com/blog/2009/10/16/saving-a-view-as-an-image/)...

 - (void)takeScreenshot {

    UIWindow *theScreen = [[UIApplication sharedApplication].windows objectAtIndex:0];     
    UIGraphicsBeginImageContext(theScreen.frame.size);  
    [[theScreen layer] renderInContext:UIGraphicsGetCurrentContext()];   
    UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();              
    [self doSomethingWith:screenshot]; 
}

我按照我想要的方式工作，但截图的图像质量比我用相机拍摄的图像差。有办法克服这个吗？我想这是因为这需要一个截图，捕获的iPhone屏幕的分辨率，而不是相机的分辨率 - 也许？

I have it working as I want but the image quality of the screenshot is much worse than the image I take with my camera. Is there a way to overcome this? I guess it is because this takes a screenshot which captures the resolution of the iPhone screen rather than the resolution of the camera - maybe?!

任何建议是伟大的： ）

Any suggestions would be great :-)

推荐答案

你是完全正确的。屏幕分辨率（320 x 480）远远小于摄像头（3G上为1200 x 1600，3GS上为1536 x 2048），因此您的UIImageView必须为320x480，并且会自动降低图片大小。这似乎很复杂，虽然 - 你已经有照片作为一个UIImage在较高的分辨率 - 你试图覆盖的东西在上面或什么？

You're exactly right. The resolution of the screen (320 x 480) is much less than the camera (1200 x 1600 on 3G, 1536 x 2048 on the 3GS) so your UIImageView must be 320x480, and it automatically downsamples your image to fit. This seems convoluted, though -- you already have the photo as a UIImage at the higher resolution -- are you trying to overlay things onto it or something?

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