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