iPhone4 iOS 在没有 NavBar 和 TabBar 的情况下截取视图？

Question

我得到了这段代码来截取视图。

UIGraphicsBeginImageContext(scrollView.bounds.size);
[scrollView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSData * data = UIImagePNGRepresentation(image);

但是，即使我将上下文设置为 320x480，滚动视图的部分内容仍然不会显示。滚动视图管理的视图可以完美地适应 320x480 框架，但它的一部分被状态栏、导航栏和 TabBar 覆盖。

我想对视图的部分进行全屏 (320x480) 屏幕截图，状态栏、TabBar 和 NavBar 可见。 有关如何执行此操作的任何指示？

一个额外的问题，可能是相关的：生成的图像使用 x1 比例，并且在视网膜显示器上看起来非常模糊，缩放需要更大的图像并将其缩小。这意味着我需要渲染 640x960 的屏幕截图来重现原始的清晰质量。我该怎么做呢？

谢谢！

Answer 1

我在这个网站上找到了以下内容：http://www.icodeblog.com/2009/07/27/1188/

UIGraphicsBeginImageContext(YourView.frame.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);

您可能还想查看这个（Apple 的如何制作屏幕截图的示例）：http://developer.apple.com/library/ios/#qa/qa1703/_index.html

Answer 2

先进行全屏截图：

// Create a graphics context with the target size
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
CGSize imageSize = [[UIScreen mainScreen] bounds].size;
if (NULL != UIGraphicsBeginImageContextWithOptions)
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);
else
    UIGraphicsBeginImageContext(imageSize);

CGContextRef context = UIGraphicsGetCurrentContext();

// Iterate over every window from back to front
for (UIWindow *window in [[UIApplication sharedApplication] windows]) 
{
    if (![window respondsToSelector:@selector(screen)] || [window screen] == [UIScreen mainScreen])
    {

        // -renderInContext: renders in the coordinate space of the layer,
        // so we must first apply the layer's geometry to the graphics context
        CGContextSaveGState(context);
        // Center the context around the window's anchor point
        CGContextTranslateCTM(context, [window center].x, [window center].y);
        // Apply the window's transform about the anchor point
        CGContextConcatCTM(context, [window transform]);
        // Offset by the portion of the bounds left of and above the anchor point
        CGContextTranslateCTM(context,
                              -[window bounds].size.width * [[window layer] anchorPoint].x,
                              -[window bounds].size.height * [[window layer] anchorPoint].y);

        // Render the layer hierarchy to the current context
        [[window layer] renderInContext:context];

        // Restore the context
        CGContextRestoreGState(context);
    }
}

// Retrieve the screenshot image
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();

然后裁剪到合适的大小

CGImageRef subImageRef = CGImageCreateWithImageInRect(screenshot.CGImage, rect);
CGRect smallBounds = CGRectMake(0, 64, 320, 372); //You should remove the hard coded numbers

UIGraphicsBeginImageContext(smallBounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, smallBounds, subImageRef);
UIImage* cropped = [UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContext();