UIImage图像旋转

 

 

【https://gist.github.com/1531596】

@interface UIImage (fixOrientation)

 

- (UIImage *)fixOrientation;

 

@end

 

@implementation UIImage (fixOrientation)

 

- (UIImage *)fixOrientation {

 

     // No-op if the orientation is already correct

     if (self.imageOrientation == UIImageOrientationUp) return self;

 

     // We need to calculate the proper transformation to make the image upright.

     // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.

     CGAffineTransform transform = CGAffineTransformIdentity;

 

     switch (self.imageOrientation) {

         case UIImageOrientationDown:

         case UIImageOrientationDownMirrored:

             transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);

             transform = CGAffineTransformRotate(transform, M_PI);

             break;

 

         case UIImageOrientationLeft:

         case UIImageOrientationLeftMirrored:

             transform = CGAffineTransformTranslate(transform, self.size.width, 0);

             transform = CGAffineTransformRotate(transform, M_PI_2);

             break;

 

         case UIImageOrientationRight:

         case UIImageOrientationRightMirrored:

             transform = CGAffineTransformTranslate(transform, 0, self.size.height);

             transform = CGAffineTransformRotate(transform, -M_PI_2);

             break;

     }

 

     switch (self.imageOrientation) {

         case UIImageOrientationUpMirrored:

         case UIImageOrientationDownMirrored:

             transform = CGAffineTransformTranslate(transform, self.size.width, 0);

             transform = CGAffineTransformScale(transform, -1, 1);

             break;

 

         case UIImageOrientationLeftMirrored:

         case UIImageOrientationRightMirrored:

             transform = CGAffineTransformTranslate(transform, self.size.height, 0);

             transform = CGAffineTransformScale(transform, -1, 1);

             break;

     }

 

     // Now we draw the underlying CGImage into a new context, applying the transform

     // calculated above.

     CGContextRef ctx = CGBitmapContextCreate(NULL, self.size.width, self.size.height,

                                              CGImageGetBitsPerComponent(self.CGImage), 0,

                                              CGImageGetColorSpace(self.CGImage),

                                              CGImageGetBitmapInfo(self.CGImage));

     CGContextConcatCTM(ctx, transform);

     switch (self.imageOrientation) {

         case UIImageOrientationLeft:

         case UIImageOrientationLeftMirrored:

         case UIImageOrientationRight:

         case UIImageOrientationRightMirrored:

             // Grr...

             CGContextDrawImage(ctx, CGRectMake(0,0,self.size.height,self.size.width), self.CGImage);

             break;

 

         default:

             CGContextDrawImage(ctx, CGRectMake(0,0,self.size.width,self.size.height), self.CGImage);

             break;

     }

 

     // And now we just create a new UIImage from the drawing context

     CGImageRef cgimg = CGBitmapContextCreateImage(ctx);

     UIImage *img = [UIImage imageWithCGImage:cgimg];

     CGContextRelease(ctx);

     CGImageRelease(cgimg);

     return img;

}

 

@end