在保存为PNG之前将新创建的iOS图像旋转90度

Question

我已经阅读了许多与此相关的答案,但我仍然无法让它发挥作用.

我有一个用户可以在其中签名的视图.以下是它的外观:http://d.pr/i/McuE

我可以成功检索此图像并将其保存到文件系统,但我需要在保存前将其旋转90度,以便签名从左到右读取.

// Grab the image
UIGraphicsBeginImageContext(self.signArea.bounds.size);
[self.signArea drawRect: self.signArea.bounds];
UIImage *signatureImage = UIGraphicsGetImageFromCurrentImageContext();

//-- ? -- Rotate the image (this doesn't work) -- ? --
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRotateCTM(context, M_PI_2);

UIGraphicsEndImageContext();

//Save the image as a PNG in Documents folder
[UIImagePNGRepresentation(signatureImage) writeToFile:[[PPHelpers documentsPath] stringByAppendingPathComponent:@"signature-temp.png"] atomically:YES];

如何在保存之前旋转图像？

在此先感谢您的帮助.我使用iOS 7 SDK在Xcode 5上.

Answer 1

我终于使用这篇文章中的一个答案来解决这个问题:如何将UIImage旋转90度？

我用这个方法:

- (UIImage *)imageRotatedByDegrees:(UIImage*)oldImage deg:(CGFloat)degrees{
  //Calculate the size of the rotated view's containing box for our drawing space
  UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,oldImage.size.width, oldImage.size.height)];
  CGAffineTransform t = CGAffineTransformMakeRotation(degrees * M_PI / 180);
  rotatedViewBox.transform = t;
  CGSize rotatedSize = rotatedViewBox.frame.size;

  //Create the bitmap context
  UIGraphicsBeginImageContext(rotatedSize);
  CGContextRef bitmap = UIGraphicsGetCurrentContext();

  //Move the origin to the middle of the image so we will rotate and scale around the center.
  CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

  //Rotate the image context
  CGContextRotateCTM(bitmap, (degrees * M_PI / 180));

  //Now, draw the rotated/scaled image into the context
  CGContextScaleCTM(bitmap, 1.0, -1.0);
  CGContextDrawImage(bitmap, CGRectMake(-oldImage.size.width / 2, -oldImage.size.height / 2, oldImage.size.width, oldImage.size.height), [oldImage CGImage]);

  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return newImage;
}

然后这样叫:

//Rotate it
UIImage *rotatedImage = [self imageRotatedByDegrees:signatureImage deg:90];

感谢大家.