UIImage+Resize.m

//
//  UIImage+Resize.m
//
//  Created by Olivier Halligon on 12/08/09.
//  Copyright 2009 AliSoftware. All rights reserved.
//

#import "UIImage+Resize.h"

@implementation UIImage (ResizeCategory)

-(UIImage*)resizedImageToSize:(CGSize)dstSize
{
	CGImageRef imgRef = self.CGImage;
	// the below values are regardless of orientation : for UIImages from Camera, width>height (landscape)
	CGSize  srcSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); // not equivalent to self.size (which is dependant on the imageOrientation)!
	
    /* Don't resize if we already meet the required destination size. */
    if (CGSizeEqualToSize(srcSize, dstSize)) {
        return self;
    }
    
	CGFloat scaleRatio = dstSize.width / srcSize.width;
	UIImageOrientation orient = self.imageOrientation;
	CGAffineTransform transform = CGAffineTransformIdentity;
	switch(orient) {
			
		case UIImageOrientationUp: //EXIF = 1
			transform = CGAffineTransformIdentity;
			break;
			
		case UIImageOrientationUpMirrored: //EXIF = 2
			transform = CGAffineTransformMakeTranslation(srcSize.width, 0.0);
			transform = CGAffineTransformScale(transform, -1.0, 1.0);
			break;
			
		case UIImageOrientationDown: //EXIF = 3
			transform = CGAffineTransformMakeTranslation(srcSize.width, srcSize.height);
			transform = CGAffineTransformRotate(transform, M_PI);
			break;
			
		case UIImageOrientationDownMirrored: //EXIF = 4
			transform = CGAffineTransformMakeTranslation(0.0, srcSize.height);
			transform = CGAffineTransformScale(transform, 1.0, -1.0);
			break;
			
		case UIImageOrientationLeftMirrored: //EXIF = 5
			dstSize = CGSizeMake(dstSize.height, dstSize.width);
			transform = CGAffineTransformMakeTranslation(srcSize.height, srcSize.width);
			transform = CGAffineTransformScale(transform, -1.0, 1.0);
			transform = CGAffineTransformRotate(transform, 3.0 * M_PI_2);
			break;  
			
		case UIImageOrientationLeft: //EXIF = 6  
			dstSize = CGSizeMake(dstSize.height, dstSize.width);
			transform = CGAffineTransformMakeTranslation(0.0, srcSize.width);
			transform = CGAffineTransformRotate(transform, 3.0 * M_PI_2);
			break;  
			
		case UIImageOrientationRightMirrored: //EXIF = 7  
			dstSize = CGSizeMake(dstSize.height, dstSize.width);
			transform = CGAffineTransformMakeScale(-1.0, 1.0);
			transform = CGAffineTransformRotate(transform, M_PI_2);
			break;  
			
		case UIImageOrientationRight: //EXIF = 8  
			dstSize = CGSizeMake(dstSize.height, dstSize.width);
			transform = CGAffineTransformMakeTranslation(srcSize.height, 0.0);
			transform = CGAffineTransformRotate(transform, M_PI_2);
			break;  
			
		default:  
			[NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];  
			
	}  
	
	/////////////////////////////////////////////////////////////////////////////
	// The actual resize: draw the image on a new context, applying a transform matrix
	UIGraphicsBeginImageContextWithOptions(dstSize, NO, self.scale);
	
	CGContextRef context = UIGraphicsGetCurrentContext();
    
       if (!context) {
           return nil;
       }
	
	if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
		CGContextScaleCTM(context, -scaleRatio, scaleRatio);
		CGContextTranslateCTM(context, -srcSize.height, 0);
	} else {  
		CGContextScaleCTM(context, scaleRatio, -scaleRatio);
		CGContextTranslateCTM(context, 0, -srcSize.height);
	}
	
	CGContextConcatCTM(context, transform);
	
	// we use srcSize (and not dstSize) as the size to specify is in user space (and we use the CTM to apply a scaleRatio)
	CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, srcSize.width, srcSize.height), imgRef);
	UIImage* resizedImage = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();
	
	return resizedImage;
}



/////////////////////////////////////////////////////////////////////////////



-(UIImage*)resizedImageToFitInSize:(CGSize)boundingSize scaleIfSmaller:(BOOL)scale
{
	// get the image size (independant of imageOrientation)
	CGImageRef imgRef = self.CGImage;
	CGSize srcSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); // not equivalent to self.size (which depends on the imageOrientation)!

	// adjust boundingSize to make it independant on imageOrientation too for farther computations
	UIImageOrientation orient = self.imageOrientation;  
	switch (orient) {
		case UIImageOrientationLeft:
		case UIImageOrientationRight:
		case UIImageOrientationLeftMirrored:
		case UIImageOrientationRightMirrored:
			boundingSize = CGSizeMake(boundingSize.height, boundingSize.width);
			break;
        default:
            // NOP
            break;
	}

	// Compute the target CGRect in order to keep aspect-ratio
	CGSize dstSize;
	
	if ( !scale && (srcSize.width < boundingSize.width) && (srcSize.height < boundingSize.height) ) {
		//NSLog(@"Image is smaller, and we asked not to scale it in this case (scaleIfSmaller:NO)");
		dstSize = srcSize; // no resize (we could directly return 'self' here, but we draw the image anyway to take image orientation into account)
	} else {		
		CGFloat wRatio = boundingSize.width / srcSize.width;
		CGFloat hRatio = boundingSize.height / srcSize.height;
		
		if (wRatio < hRatio) {
			//NSLog(@"Width imposed, Height scaled ; ratio = %f",wRatio);
			dstSize = CGSizeMake(boundingSize.width, floorf(srcSize.height * wRatio));
		} else {
			//NSLog(@"Height imposed, Width scaled ; ratio = %f",hRatio);
			dstSize = CGSizeMake(floorf(srcSize.width * hRatio), boundingSize.height);
		}
	}
		
	return [self resizedImageToSize:dstSize];
}

@end