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UIImage+Resize.m
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UIImage+Resize.m
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// UIImage+Resize.m
// Created by Trevor Harmon on 8/5/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
#import "UIImage+Resize.h"
#import "UIImage+RoundedCorner.h"
#import "UIImage+Alpha.h"
@implementation UIImage (Resize)
// Returns a copy of this image that is cropped to the given bounds.
// The bounds will be adjusted using CGRectIntegral.
// This method ignores the image's imageOrientation setting.
- (UIImage *)croppedImage:(CGRect)bounds {
CGFloat scale = MAX(self.scale, 1.0f);
CGRect scaledBounds = CGRectMake(bounds.origin.x * scale, bounds.origin.y * scale, bounds.size.width * scale, bounds.size.height * scale);
CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], scaledBounds);
UIImage *croppedImage = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:UIImageOrientationUp];
CGImageRelease(imageRef);
return croppedImage;
}
// Returns a copy of this image that is squared to the thumbnail size.
// If transparentBorder is non-zero, a transparent border of the given size will be added around the edges of the thumbnail. (Adding a transparent border of at least one pixel in size has the side-effect of antialiasing the edges of the image when rotating it using Core Animation.)
- (UIImage *)thumbnailImage:(NSInteger)thumbnailSize
transparentBorder:(NSUInteger)borderSize
cornerRadius:(NSUInteger)cornerRadius
interpolationQuality:(CGInterpolationQuality)quality {
UIImage *resizedImage = [self resizedImageWithContentMode:UIViewContentModeScaleAspectFill
bounds:CGSizeMake(thumbnailSize, thumbnailSize)
interpolationQuality:quality];
// Crop out any part of the image that's larger than the thumbnail size
// The cropped rect must be centered on the resized image
// Round the origin points so that the size isn't altered when CGRectIntegral is later invoked
CGRect cropRect = CGRectMake(round((resizedImage.size.width - thumbnailSize) / 2),
round((resizedImage.size.height - thumbnailSize) / 2),
thumbnailSize,
thumbnailSize);
UIImage *croppedImage = [resizedImage croppedImage:cropRect];
UIImage *transparentBorderImage = borderSize ? [croppedImage transparentBorderImage:borderSize] : croppedImage;
return [transparentBorderImage roundedCornerImage:cornerRadius borderSize:borderSize];
}
// Returns a rescaled copy of the image, taking into account its orientation
// The image will be scaled disproportionately if necessary to fit the bounds specified by the parameter
- (UIImage *)resizedImage:(CGSize)newSize interpolationQuality:(CGInterpolationQuality)quality {
BOOL drawTransposed;
switch ( self.imageOrientation )
{
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
drawTransposed = YES;
break;
default:
drawTransposed = NO;
}
CGAffineTransform transform = [self transformForOrientation:newSize];
return [self resizedImage:newSize transform:transform drawTransposed:drawTransposed interpolationQuality:quality];
}
// Resizes the image according to the given content mode, taking into account the image's orientation
- (UIImage *)resizedImageWithContentMode:(UIViewContentMode)contentMode
bounds:(CGSize)bounds
interpolationQuality:(CGInterpolationQuality)quality {
CGFloat horizontalRatio = bounds.width / self.size.width;
CGFloat verticalRatio = bounds.height / self.size.height;
CGFloat ratio;
switch (contentMode) {
case UIViewContentModeScaleAspectFill:
ratio = MAX(horizontalRatio, verticalRatio);
break;
case UIViewContentModeScaleAspectFit:
ratio = MIN(horizontalRatio, verticalRatio);
break;
default:
[NSException raise:NSInvalidArgumentException format:@"Unsupported content mode: %ld", (long)contentMode];
}
CGSize newSize = CGSizeMake(self.size.width * ratio, self.size.height * ratio);
return [self resizedImage:newSize interpolationQuality:quality];
}
#pragma mark -
#pragma mark Private helper methods
// Returns a copy of the image that has been transformed using the given affine transform and scaled to the new size
// The new image's orientation will be UIImageOrientationUp, regardless of the current image's orientation
// If the new size is not integral, it will be rounded up
- (UIImage *)resizedImage:(CGSize)newSize
transform:(CGAffineTransform)transform
drawTransposed:(BOOL)transpose
interpolationQuality:(CGInterpolationQuality)quality {
CGFloat scale = MAX(1.0f, self.scale);
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width*scale, newSize.height*scale));
CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
CGImageRef imageRef = self.CGImage;
// Fix for a colorspace / transparency issue that affects some types of
// images. See here: http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/comment-page-2/#comment-39951
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmap = CGBitmapContextCreate(
NULL,
newRect.size.width,
newRect.size.height,
8, /* bits per channel */
(newRect.size.width * 4), /* 4 channels per pixel * numPixels/row */
colorSpace,
kCGImageAlphaPremultipliedLast
);
CGColorSpaceRelease(colorSpace);
// Rotate and/or flip the image if required by its orientation
CGContextConcatCTM(bitmap, transform);
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(bitmap, quality);
// Draw into the context; this scales the image
CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef scale:self.scale orientation:UIImageOrientationUp];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);
return newImage;
}
// Returns an affine transform that takes into account the image orientation when drawing a scaled image
- (CGAffineTransform)transformForOrientation:(CGSize)newSize {
CGAffineTransform transform = CGAffineTransformIdentity;
switch (self.imageOrientation) {
case UIImageOrientationDown: // EXIF = 3
case UIImageOrientationDownMirrored: // EXIF = 4
transform = CGAffineTransformTranslate(transform, newSize.width, newSize.height);
transform = CGAffineTransformRotate(transform, M_PI);
break;
case UIImageOrientationLeft: // EXIF = 6
case UIImageOrientationLeftMirrored: // EXIF = 5
transform = CGAffineTransformTranslate(transform, newSize.width, 0);
transform = CGAffineTransformRotate(transform, M_PI_2);
break;
case UIImageOrientationRight: // EXIF = 8
case UIImageOrientationRightMirrored: // EXIF = 7
transform = CGAffineTransformTranslate(transform, 0, newSize.height);
transform = CGAffineTransformRotate(transform, -M_PI_2);
break;
default:
break;
}
switch (self.imageOrientation) {
case UIImageOrientationUpMirrored: // EXIF = 2
case UIImageOrientationDownMirrored: // EXIF = 4
transform = CGAffineTransformTranslate(transform, newSize.width, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
case UIImageOrientationLeftMirrored: // EXIF = 5
case UIImageOrientationRightMirrored: // EXIF = 7
transform = CGAffineTransformTranslate(transform, newSize.height, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
default:
break;
}
return transform;
}
@end