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// UIImage+Alpha.h
// Created by Trevor Harmon on 9/20/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
// Helper methods for adding an alpha layer to an image
@interface UIImage (Alpha)
- (BOOL)hasAlpha;
- (UIImage *)imageWithAlpha;
- (UIImage *)transparentBorderImage:(NSUInteger)borderSize;
@end
// UIImage+Alpha.m
// Created by Trevor Harmon on 9/20/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
#import "UIImage+Alpha.h"
// Private helper methods
@interface UIImage ()
- (CGImageRef)newBorderMask:(NSUInteger)borderSize size:(CGSize)size;
@end
@implementation UIImage (Alpha)
// Returns true if the image has an alpha layer
- (BOOL)hasAlpha {
CGImageAlphaInfo alpha = CGImageGetAlphaInfo(self.CGImage);
return (alpha == kCGImageAlphaFirst ||
alpha == kCGImageAlphaLast ||
alpha == kCGImageAlphaPremultipliedFirst ||
alpha == kCGImageAlphaPremultipliedLast);
}
// Returns a copy of the given image, adding an alpha channel if it doesn't already have one
- (UIImage *)imageWithAlpha {
if ([self hasAlpha]) {
return self;
}
CGImageRef imageRef = self.CGImage;
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
// The bitsPerComponent and bitmapInfo values are hard-coded to prevent an "unsupported parameter combination" error
CGContextRef offscreenContext = CGBitmapContextCreate(NULL,
width,
height,
8,
0,
CGImageGetColorSpace(imageRef),
kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
// Draw the image into the context and retrieve the new image, which will now have an alpha layer
CGContextDrawImage(offscreenContext, CGRectMake(0, 0, width, height), imageRef);
CGImageRef imageRefWithAlpha = CGBitmapContextCreateImage(offscreenContext);
UIImage *imageWithAlpha = [UIImage imageWithCGImage:imageRefWithAlpha];
// Clean up
CGContextRelease(offscreenContext);
CGImageRelease(imageRefWithAlpha);
return imageWithAlpha;
}
// Returns a copy of the image with a transparent border of the given size added around its edges.
// If the image has no alpha layer, one will be added to it.
- (UIImage *)transparentBorderImage:(NSUInteger)borderSize {
// If the image does not have an alpha layer, add one
UIImage *image = [self imageWithAlpha];
CGRect newRect = CGRectMake(0, 0, image.size.width + borderSize * 2, image.size.height + borderSize * 2);
// Build a context that's the same dimensions as the new size
CGContextRef bitmap = CGBitmapContextCreate(NULL,
newRect.size.width,
newRect.size.height,
CGImageGetBitsPerComponent(self.CGImage),
0,
CGImageGetColorSpace(self.CGImage),
CGImageGetBitmapInfo(self.CGImage));
// Draw the image in the center of the context, leaving a gap around the edges
CGRect imageLocation = CGRectMake(borderSize, borderSize, image.size.width, image.size.height);
CGContextDrawImage(bitmap, imageLocation, self.CGImage);
CGImageRef borderImageRef = CGBitmapContextCreateImage(bitmap);
// Create a mask to make the border transparent, and combine it with the image
CGImageRef maskImageRef = [self newBorderMask:borderSize size:newRect.size];
CGImageRef transparentBorderImageRef = CGImageCreateWithMask(borderImageRef, maskImageRef);
UIImage *transparentBorderImage = [UIImage imageWithCGImage:transparentBorderImageRef];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(borderImageRef);
CGImageRelease(maskImageRef);
CGImageRelease(transparentBorderImageRef);
return transparentBorderImage;
}
#pragma mark -
#pragma mark Private helper methods
// Creates a mask that makes the outer edges transparent and everything else opaque
// The size must include the entire mask (opaque part + transparent border)
// The caller is responsible for releasing the returned reference by calling CGImageRelease
- (CGImageRef)newBorderMask:(NSUInteger)borderSize size:(CGSize)size {
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
// Build a context that's the same dimensions as the new size
CGContextRef maskContext = CGBitmapContextCreate(NULL,
size.width,
size.height,
8, // 8-bit grayscale
0,
colorSpace,
kCGBitmapByteOrderDefault | kCGImageAlphaNone);
// Start with a mask that's entirely transparent
CGContextSetFillColorWithColor(maskContext, [UIColor blackColor].CGColor);
CGContextFillRect(maskContext, CGRectMake(0, 0, size.width, size.height));
// Make the inner part (within the border) opaque
CGContextSetFillColorWithColor(maskContext, [UIColor whiteColor].CGColor);
CGContextFillRect(maskContext, CGRectMake(borderSize, borderSize, size.width - borderSize * 2, size.height - borderSize * 2));
// Get an image of the context
CGImageRef maskImageRef = CGBitmapContextCreateImage(maskContext);
// Clean up
CGContextRelease(maskContext);
CGColorSpaceRelease(colorSpace);
return maskImageRef;
}
@end
// UIImage+Resize.h
// Created by Trevor Harmon on 8/5/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
// Extends the UIImage class to support resizing/cropping
@interface UIImage (Resize)
- (UIImage *)croppedImage:(CGRect)bounds;
- (UIImage *)thumbnailImage:(NSInteger)thumbnailSize
transparentBorder:(NSUInteger)borderSize
cornerRadius:(NSUInteger)cornerRadius
interpolationQuality:(CGInterpolationQuality)quality;
- (UIImage *)resizedImage:(CGSize)newSize
interpolationQuality:(CGInterpolationQuality)quality;
- (UIImage *)resizedImageWithContentMode:(UIViewContentMode)contentMode
bounds:(CGSize)bounds
interpolationQuality:(CGInterpolationQuality)quality;
@end
// 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"
// Private helper methods
@interface UIImage ()
- (UIImage *)resizedImage:(CGSize)newSize
transform:(CGAffineTransform)transform
drawTransposed:(BOOL)transpose
interpolationQuality:(CGInterpolationQuality)quality;
- (CGAffineTransform)transformForOrientation:(CGSize)newSize;
@end
@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 {
CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], bounds);
UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];
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;
}
return [self resizedImage:newSize
transform:[self transformForOrientation:newSize]
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: %d", 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 {
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
CGImageRef imageRef = self.CGImage;
// Build a context that's the same dimensions as the new size
CGContextRef bitmap = CGBitmapContextCreate(NULL,
newRect.size.width,
newRect.size.height,
CGImageGetBitsPerComponent(imageRef),
0,
CGImageGetColorSpace(imageRef),
CGImageGetBitmapInfo(imageRef));
// 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];
// 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;
}
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;
}
return transform;
}
@end
// UIImage+RoundedCorner.h
// Created by Trevor Harmon on 9/20/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
// Extends the UIImage class to support making rounded corners
@interface UIImage (RoundedCorner)
- (UIImage *)roundedCornerImage:(NSInteger)cornerSize borderSize:(NSInteger)borderSize;
@end
// UIImage+RoundedCorner.m
// Created by Trevor Harmon on 9/20/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
#import "UIImage+RoundedCorner.h"
#import "UIImage+Alpha.h"
// Private helper methods
@interface UIImage ()
- (void)addRoundedRectToPath:(CGRect)rect context:(CGContextRef)context ovalWidth:(CGFloat)ovalWidth ovalHeight:(CGFloat)ovalHeight;
@end
@implementation UIImage (RoundedCorner)
// Creates a copy of this image with rounded corners
// If borderSize is non-zero, a transparent border of the given size will also be added
// Original author: Björn Sållarp. Used with permission. See: http://blog.sallarp.com/iphone-uiimage-round-corners/
- (UIImage *)roundedCornerImage:(NSInteger)cornerSize borderSize:(NSInteger)borderSize {
// If the image does not have an alpha layer, add one
UIImage *image = [self imageWithAlpha];
// Build a context that's the same dimensions as the new size
CGContextRef context = CGBitmapContextCreate(NULL,
image.size.width,
image.size.height,
CGImageGetBitsPerComponent(image.CGImage),
0,
CGImageGetColorSpace(image.CGImage),
CGImageGetBitmapInfo(image.CGImage));
// Create a clipping path with rounded corners
CGContextBeginPath(context);
[self addRoundedRectToPath:CGRectMake(borderSize, borderSize, image.size.width - borderSize * 2, image.size.height - borderSize * 2)
context:context
ovalWidth:cornerSize
ovalHeight:cornerSize];
CGContextClosePath(context);
CGContextClip(context);
// Draw the image to the context; the clipping path will make anything outside the rounded rect transparent
CGContextDrawImage(context, CGRectMake(0, 0, image.size.width, image.size.height), image.CGImage);
// Create a CGImage from the context
CGImageRef clippedImage = CGBitmapContextCreateImage(context);
CGContextRelease(context);
// Create a UIImage from the CGImage
UIImage *roundedImage = [UIImage imageWithCGImage:clippedImage];
CGImageRelease(clippedImage);
return roundedImage;
}
#pragma mark -
#pragma mark Private helper methods
// Adds a rectangular path to the given context and rounds its corners by the given extents
// Original author: Björn Sållarp. Used with permission. See: http://blog.sallarp.com/iphone-uiimage-round-corners/
- (void)addRoundedRectToPath:(CGRect)rect context:(CGContextRef)context ovalWidth:(CGFloat)ovalWidth ovalHeight:(CGFloat)ovalHeight {
if (ovalWidth == 0 || ovalHeight == 0) {
CGContextAddRect(context, rect);
return;
}
CGContextSaveGState(context);
CGContextTranslateCTM(context, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGContextScaleCTM(context, ovalWidth, ovalHeight);
CGFloat fw = CGRectGetWidth(rect) / ovalWidth;
CGFloat fh = CGRectGetHeight(rect) / ovalHeight;
CGContextMoveToPoint(context, fw, fh/2);
CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1);
CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1);
CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1);
CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1);
CGContextClosePath(context);
CGContextRestoreGState(context);
}
@end
@rromanchuk

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commented Jul 9, 2012

is this still working for ios5.1, do you have a usage example?

- (UIImage *)thumbnailImage:(NSInteger)thumbnailSize
          transparentBorder:(NSUInteger)borderSize
               cornerRadius:(NSUInteger)cornerRadius
       interpolationQuality:(CGInterpolationQuality)quality; 
@benilovj

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Owner Author

commented Jul 11, 2012

Hi Ryan, this works under 5.1 as far as i know, although I'm only using the 'resizedImage' method.

@rromanchuk

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commented Jul 11, 2012

looks like it is, thx

@jmcastel

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commented Aug 29, 2014

hello, awesome, could you make the swift version ?

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