iPad上的低质量捕获视图上下文 [英] Low quality of capture view context on iPad

问题描述

我需要捕获特定的UIView，但结果是低质量如何解决这个问题并提高质量？

I need capture specific UIView , but the result is in low quality how can fix this and increase the quality ?

UIGraphicsBeginImageContext(captureView.bounds.size);
    [captureView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
    UIImageWriteToSavedPhotosAlbum(screenshot, nil, nil, nil);
    UIGraphicsEndImageContext();

推荐答案

我想你需要捕获一个UIView / UIWindow in视网膜分辨率（960x640或2048x1536）使用UIGraphicsBeginImageContextWithOptions并设置其缩放参数0.0f使其以原始分辨率捕获（适用于iPhone 4及更高版本或iPad 3的视网膜）。

I guess you need a capture a UIView/UIWindow in retina resolution (960x640 or 2048x1536) Using UIGraphicsBeginImageContextWithOptions and set its scale parameter 0.0f makes it capture in native resolution (retina for iPhone 4 and later or iPad 3).

代码以原始分辨率捕获你的UIView

This code capture your UIView in native resolution

CGRect rect = [captureView bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[captureView.layer renderInContext:context];   
UIImage *capturedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

这个全屏相同（关键窗口）

This one does the same for full screen (key window)

UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];
CGRect rect = [keyWindow bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[keyWindow.layer renderInContext:context];   
UIImage *capturedScreen = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

这可以在应用程序的文档文件夹中以99％的质量保存Upgmage格式

This saves the UIImage in jpg format with 95% quality in the app's document folder

NSString  *imagePath = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/capturedImage.jpg"]];    
[UIImageJPEGRepresentation(capturedImage, 0.95) writeToFile:imagePath atomically:YES];

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