ios 图片方向纠正

- (UIImage *)fixOrientation:(UIImage *)srcImg {
if (srcImg.imageOrientation == UIImageOrientationUp) return srcImg;
CGAffineTransform transform = CGAffineTransformIdentity;
switch (srcImg.imageOrientation) {
case UIImageOrientationDown:
case UIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, srcImg.size.width, srcImg.size.height);
transform = CGAffineTransformRotate(transform, M_PI);
break;

case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
transform = CGAffineTransformTranslate(transform, srcImg.size.width, 0);
transform = CGAffineTransformRotate(transform, M_PI_2);
break;

case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, 0, srcImg.size.height);
transform = CGAffineTransformRotate(transform, -M_PI_2);
break;
case UIImageOrientationUp:
case UIImageOrientationUpMirrored:
break;
}

switch (srcImg.imageOrientation) {
case UIImageOrientationUpMirrored:
case UIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, srcImg.size.width, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;

case UIImageOrientationLeftMirrored:
case UIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, srcImg.size.height, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
case UIImageOrientationUp:
case UIImageOrientationDown:
case UIImageOrientationLeft:
case UIImageOrientationRight:
break;
}

CGContextRef ctx = CGBitmapContextCreate(NULL, srcImg.size.width, srcImg.size.height,
CGImageGetBitsPerComponent(srcImg.CGImage), 0,
CGImageGetColorSpace(srcImg.CGImage),
CGImageGetBitmapInfo(srcImg.CGImage));
CGContextConcatCTM(ctx, transform);
switch (srcImg.imageOrientation) {
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
CGContextDrawImage(ctx, CGRectMake(0,0,srcImg.size.height,srcImg.size.width), srcImg.CGImage);
break;

default:
CGContextDrawImage(ctx, CGRectMake(0,0,srcImg.size.width,srcImg.size.height), srcImg.CGImage);
break;
}

CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
UIImage *img = [UIImage imageWithCGImage:cgimg];
CGContextRelease(ctx);
CGImageRelease(cgimg);
return img;
}