iPhone下旋转UIImage

来源：苹果开发中文网 www.cocoadev.cn

+(UIImage *)rotateImage:(UIImage *)aImage

{

CGImageRef imgRef = aImage.CGImage;

CGFloat width = CGImageGetWidth(imgRef);

CGFloat height = CGImageGetHeight(imgRef);

CGAffineTransform transform = CGAffineTransformIdentity;

CGRect bounds = CGRectMake(0, 0, width, height);

CGFloat scaleRatio = 1;

CGFloat boundHeight;

UIImageOrientation orient = aImage.imageOrientation;

switch(orient)

{

case UIImageOrientationUp: //EXIF = 1

transform = CGAffineTransformIdentity;

break;

case UIImageOrientationUpMirrored: //EXIF = 2

transform = CGAffineTransformMakeTranslation(width, 0.0);

transform = CGAffineTransformScale(transform, -1.0, 1.0);

break;

case UIImageOrientationDown: //EXIF = 3

transform = CGAffineTransformMakeTranslation(width, height);

transform = CGAffineTransformRotate(transform, M_PI);

break;

case UIImageOrientationDownMirrored: //EXIF = 4

transform = CGAffineTransformMakeTranslation(0.0, 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(height, 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, 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(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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