在保存为PNG之前将新创建的iOS图像旋转90度 [英] Rotate Newly Created iOS Image 90 Degrees Prior to Saving as PNG

问题描述

我已经阅读了很多与此相关的答案，但我仍然无法让它工作。

I have read numerous answers related to this, but I still can't get it to work.

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

I have a view where a user can sign their name. Here's how it looks: 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，但我需要在保存之前将其旋转90度，以便签名从左到右读取。

I can successfully retrieve this image and save it to the file system, but I need to rotate it 90 degrees before saving so the signature reads from left-to-right.

// 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？

How can I rotate the image prior to saving?

提前感谢您的帮助。我使用iOS 7 SDK在Xcode 5上。

Thanks in advance for your help. I'm on Xcode 5 using the iOS 7 SDK.

推荐答案

我终于使用其中一个答案来解决这个问题了发布：如何将UIImage旋转90度？

I finally got this to work using one of the answers on this post: How to Rotate a UIImage 90 degrees?

我用过这种方法：

- (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;
}

然后将其称为：

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

谢谢大家。

这篇关于在保存为PNG之前将新创建的iOS图像旋转90度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！