Created
May 12, 2011 08:17
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UIImage scale and rotate based on exif flag
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UIImage *scaleAndRotateImage(UIImage *image) | |
{ | |
int kMaxResolution = 1920; | |
CGImageRef imgRef = image.CGImage; | |
CGFloat width = CGImageGetWidth(imgRef); | |
CGFloat height = CGImageGetHeight(imgRef); | |
CGAffineTransform transform = CGAffineTransformIdentity; | |
CGRect bounds = CGRectMake(0, 0, width, height); | |
if (width > kMaxResolution || height > kMaxResolution) { | |
CGFloat ratio = width/height; | |
if (ratio > 1) { | |
bounds.size.width = kMaxResolution; | |
bounds.size.height = bounds.size.width / ratio; | |
} | |
else { | |
bounds.size.height = kMaxResolution; | |
bounds.size.width = bounds.size.height * ratio; | |
} | |
} | |
CGFloat scaleRatio = bounds.size.width / width; | |
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); | |
CGFloat boundHeight; | |
UIImageOrientation orient = image.imageOrientation; | |
switch(orient) { | |
case UIImageOrientationUp: //EXIF = 1 | |
transform = CGAffineTransformIdentity; | |
break; | |
case UIImageOrientationUpMirrored: //EXIF = 2 | |
transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0); | |
transform = CGAffineTransformScale(transform, -1.0, 1.0); | |
break; | |
case UIImageOrientationDown: //EXIF = 3 | |
transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height); | |
transform = CGAffineTransformRotate(transform, M_PI); | |
break; | |
case UIImageOrientationDownMirrored: //EXIF = 4 | |
transform = CGAffineTransformMakeTranslation(0.0, imageSize.height); | |
transform = CGAffineTransformScale(transform, 1.0, -1.0); | |
break; | |
case UIImageOrientationLeftMirrored: //EXIF = 5 | |
boundHeight = bounds.size.height; | |
bounds.size.height = bounds.size.width; | |
bounds.size.width = boundHeight; | |
transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width); | |
transform = CGAffineTransformScale(transform, -1.0, 1.0); | |
transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0); | |
break; | |
case UIImageOrientationLeft: //EXIF = 6 | |
boundHeight = bounds.size.height; | |
bounds.size.height = bounds.size.width; | |
bounds.size.width = boundHeight; | |
transform = CGAffineTransformMakeTranslation(0.0, imageSize.width); | |
transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0); | |
break; | |
case UIImageOrientationRightMirrored: //EXIF = 7 | |
boundHeight = bounds.size.height; | |
bounds.size.height = bounds.size.width; | |
bounds.size.width = boundHeight; | |
transform = CGAffineTransformMakeScale(-1.0, 1.0); | |
transform = CGAffineTransformRotate(transform, M_PI / 2.0); | |
break; | |
case UIImageOrientationRight: //EXIF = 8 | |
boundHeight = bounds.size.height; | |
bounds.size.height = bounds.size.width; | |
bounds.size.width = boundHeight; | |
transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0); | |
transform = CGAffineTransformRotate(transform, M_PI / 2.0); | |
break; | |
default: | |
[NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"]; | |
} | |
UIGraphicsBeginImageContext(bounds.size); | |
CGContextRef context = UIGraphicsGetCurrentContext(); | |
if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) { | |
CGContextScaleCTM(context, -scaleRatio, scaleRatio); | |
CGContextTranslateCTM(context, -height, 0); | |
} | |
else { | |
CGContextScaleCTM(context, scaleRatio, -scaleRatio); | |
CGContextTranslateCTM(context, 0, -height); | |
} | |
CGContextConcatCTM(context, transform); | |
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef); | |
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext(); | |
UIGraphicsEndImageContext(); | |
return imageCopy; | |
} |
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