iPhone iOS如何通过旋转以编程方式截取屏幕截图？

Question

我知道如何截取 iPhone/iPad 屏幕的常规矩形屏幕截图（代码如下）。但是，我正在寻找一种方法来获取旋转任意度数的屏幕截图

如何使用任意旋转的矩形截取UIView的截图？

    //this is the rotation of the rectangle
        NSNumber* savedRotation = [NSNumber numberWithFloat: 0.35]; //radians, get the real number from a gesture recognizer

        //create a screenshot
        CGSize screenshotSize;

//screenshot size has to be adjusted for the rotation, or multiplied by the square root of 2
        if( UIDeviceOrientationIsLandscape([[UIApplication sharedApplication]statusBarOrientation]))
        {
            screenshotSize  =  CGSizeMake(1024,768);
        }else
        {
            screenshotSize  =  CGSizeMake(768, 1024);

        }

        if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)])
            UIGraphicsBeginImageContextWithOptions(screenshotSize, NO, [UIScreen mainScreen].scale);


        else
            UIGraphicsBeginImageContext(screenshotSize);

        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSaveGState(context);

    //this does the proper rotation, but there's some kind of extra translation required to make it capture what's under the rectangle
        CGContextRotateCTM(context, -savedRotation.floatValue);
        [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];


        UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();

        CGContextRestoreGState(context);

这是上面代码的结果，它似乎部分工作，但需要对 CTM 进行一些额外的翻译才能完美匹配捕获矩形。此外，我需要将上下文的边界更改为更宽（可能是 1024 * sqrt(2) 宽度和高度），以允许任何旋转而不进行裁剪。

Answer 1

以下是根据简单矩形裁剪图像所需的代码。

我不确定您如何跟踪矩形的旋转，但从那里应用此解决方案应该非常简单；

// Create rectangle from middle of current image
CGRect croprect = CGRectMake(image.size.width / 4, image.size.height / 4 ,
(image.size.width / 2), (image.size.height / 2));

// Draw new image in current graphics context
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], croprect);

// Create new cropped UIImage
UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];

CGImageRelease(imageRef);

希望对你有帮助。