iphone - iPad 上捕获 View 上下文的质量低下

Question

我需要捕获特定的 UIView，但结果质量很差如何解决这个问题并提高质量？

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

Answer 1

我想您需要使用 UIGraphicsBeginImageContextWithOptions 以视网膜分辨率(960x640 或 2048x1536)捕获 UIView/UIWindow 并将其缩放参数设置为 0.0f 以使其以原始分辨率(iPhone 4 及更高版本或 iPad 3 的视网膜)捕获。

此代码以原始分辨率捕获您的 UIView

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

这个对全屏(关键窗口)做同样的事情

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();

这会以 95% 的质量将 UIImage 以 jpg 格式保存在应用程序的文档文件夹中

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