I have a UIImage that is UIImageOrientationUp (portrait) that I would like to rotate counter-clockwise by 90 degrees (to landscape). I don't want to use a CGAffineTransform. I want the pixels of the UIImage to actually shift position. I am using a block of code (shown below) originally intended to resize a UIImage to do this. I set a target size as the current size of the UIImage but I get an error:
(Error): CGBitmapContextCreate: invalid data bytes/row: should be at least 1708 for 8 integer bits/component, 3 components, kCGImageAlphaPremultipliedLast.
(I don't get an error whenever I provide a SMALLER size as the target size BTW). How can I ROTATE my UIImage 90 degrees CCW using just core graphics functions while preserving the current size?
-(UIImage*)reverseImageByScalingToSize:(CGSize)targetSize:(UIImage*)anImage
{
UIImage* sourceImage = anImage;
CGFloat targetWidth = targetSize.height;
CGFloat targetHeight = targetSize.width;
CGImageRef imageRef = [sourceImage CGImage];
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);
if (bitmapInfo == kCGImageAlphaNone) {
bitmapInfo = kCGImageAlphaNoneSkipLast;
}
CGContextRef bitmap;
if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);
} else {
bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);
}
if (sourceImage.imageOrientation == UIImageOrientationRight) {
CGContextRotateCTM (bitmap, radians(90));
CGContextTranslateCTM (bitmap, 0, -targetHeight);
} else if (sourceImage.imageOrientation == UIImageOrientationLeft) {
CGContextRotateCTM (bitmap, radians(-90));
CGContextTranslateCTM (bitmap, -targetWidth, 0);
} else if (sourceImage.imageOrientation == UIImageOrientationDown) {
// NOTHING
} else if (sourceImage.imageOrientation == UIImageOrientationUp) {
CGContextRotateCTM (bitmap, radians(90));
CGContextTranslateCTM (bitmap, 0, -targetHeight);
}
CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth, targetHeight), imageRef);
CGImageRef ref = CGBitmapContextCreateImage(bitmap);
UIImage* newImage = [UIImage imageWithCGImage:ref];
CGContextRelease(bitmap);
CGImageRelease(ref);
return newImage;
}
This question is related to
ios
objective-c
uiimage
uikit
core-graphics
I believe the easiest way (and thread safe too) is to do:
//assume that the image is loaded in landscape mode from disk
UIImage * landscapeImage = [UIImage imageNamed:imgname];
UIImage * portraitImage = [[UIImage alloc] initWithCGImage: landscapeImage.CGImage
scale: 1.0
orientation: UIImageOrientationRight];
Note: As Brainware said this only modifies the orientation data of the image - the pixel data is untouched. For some applications, this may not be enough.
Or in Swift:
guard
let landscapeImage = UIImage(named: "imgname"),
let landscapeCGImage = landscapeImage.cgImage
else { return }
let portraitImage = UIImage(cgImage: landscapeCGImage, scale: landscapeImage.scale, orientation: .right)
I like the simple elegance of Peter Sarnowski's answer, but it can cause problems when you can't rely on EXIF metadata and the like. In situations where you need to rotate the actual image data I would recommend something like this:
- (UIImage *)rotateImage:(UIImage *) img
{
CGSize imgSize = [img size];
UIGraphicsBeginImageContext(imgSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRotateCTM(context, M_PI_2);
CGContextTranslateCTM(context, 0, -640);
[img drawInRect:CGRectMake(0, 0, imgSize.height, imgSize.width)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
The above code takes an image whose orientation is Landscape (can't remember if it's Landscape Left or Landscape Right) and rotates it into Portrait. It is an example which can be modified for your needs.
The key arguments you would have to play with are CGContextRotateCTM(context, M_PI_2) where you decide how much you want to rotate by, but then you have to make sure the picture still draws on the screen using CGContextTranslateCTM(context, 0, -640). This last part is quite important to make sure you see the image and not a blank screen.
For more info check out the source.
If you want to add a photo rotate button that'll keep rotating the photo in 90 degree increments, here you go. (finalImage is a UIImage that's already been created elsewhere.)
- (void)rotatePhoto {
UIImage *rotatedImage;
if (finalImage.imageOrientation == UIImageOrientationRight)
rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
scale: 1.0
orientation: UIImageOrientationDown];
else if (finalImage.imageOrientation == UIImageOrientationDown)
rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
scale: 1.0
orientation: UIImageOrientationLeft];
else if (finalImage.imageOrientation == UIImageOrientationLeft)
rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
scale: 1.0
orientation: UIImageOrientationUp];
else
rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
scale: 1.0
orientation: UIImageOrientationRight];
finalImage = rotatedImage;
}
A thread safe rotation function is the following (it works much better):
-(UIImage*)imageByRotatingImage:(UIImage*)initImage fromImageOrientation:(UIImageOrientation)orientation
{
CGImageRef imgRef = initImage.CGImage;
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
CGFloat boundHeight;
UIImageOrientation orient = orientation;
switch(orient) {
case UIImageOrientationUp: //EXIF = 1
return initImage;
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"];
}
// Create the bitmap context
CGContextRef context = NULL;
void * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow = (bounds.size.width * 4);
bitmapByteCount = (bitmapBytesPerRow * bounds.size.height);
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
return nil;
}
// Create the bitmap context. We want pre-multiplied ARGB, 8-bits
// per component. Regardless of what the source image format is
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.
CGColorSpaceRef colorspace = CGImageGetColorSpace(imgRef);
context = CGBitmapContextCreate (bitmapData,bounds.size.width,bounds.size.height,8,bitmapBytesPerRow,
colorspace, kCGBitmapAlphaInfoMask & kCGImageAlphaPremultipliedLast);
if (context == NULL)
// error creating context
return nil;
CGContextScaleCTM(context, -1.0, -1.0);
CGContextTranslateCTM(context, -bounds.size.width, -bounds.size.height);
CGContextConcatCTM(context, transform);
// Draw the image to the bitmap context. Once we draw, the memory
// allocated for the context for rendering will then contain the
// raw image data in the specified color space.
CGContextDrawImage(context, CGRectMake(0,0,width, height), imgRef);
CGImageRef imgRef2 = CGBitmapContextCreateImage(context);
CGContextRelease(context);
free(bitmapData);
UIImage * image = [UIImage imageWithCGImage:imgRef2 scale:initImage.scale orientation:UIImageOrientationUp];
CGImageRelease(imgRef2);
return image;
}
I try this code, it works, and took from http://www.catamount.com/blog/1015/uiimage-extensions-for-cutting-scaling-and-rotating-uiimages/
+ (UIImage *)rotateImage:(UIImage*)src byRadian:(CGFloat)radian
{
// calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0, src.size.width, src.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(radian);
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
// // Rotate the image context
CGContextRotateCTM(bitmap, radian);
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-src.size.width / 2, -src.size.height / 2, src.size.width, src.size.height), [src CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Swift 3 UIImage extension:
func fixOrientation() -> UIImage {
// No-op if the orientation is already correct
if ( self.imageOrientation == .up ) {
return self;
}
// We need to calculate the proper transformation to make the image upright.
// We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
var transform: CGAffineTransform = .identity
if ( self.imageOrientation == .down || self.imageOrientation == .downMirrored ) {
transform = transform.translatedBy(x: self.size.width, y: self.size.height)
transform = transform.rotated(by: .pi)
}
if ( self.imageOrientation == .left || self.imageOrientation == .leftMirrored ) {
transform = transform.translatedBy(x: self.size.width, y: 0)
transform = transform.rotated(by: .pi/2)
}
if ( self.imageOrientation == .right || self.imageOrientation == .rightMirrored ) {
transform = transform.translatedBy(x: 0, y: self.size.height);
transform = transform.rotated(by: -.pi/2);
}
if ( self.imageOrientation == .upMirrored || self.imageOrientation == .downMirrored ) {
transform = transform.translatedBy(x: self.size.width, y: 0)
transform = transform.scaledBy(x: -1, y: 1)
}
if ( self.imageOrientation == .leftMirrored || self.imageOrientation == .rightMirrored ) {
transform = transform.translatedBy(x: self.size.height, y: 0);
transform = transform.scaledBy(x: -1, y: 1);
}
// Now we draw the underlying CGImage into a new context, applying the transform
// calculated above.
let ctx: CGContext = CGContext(data: nil, width: Int(self.size.width), height: Int(self.size.height),
bitsPerComponent: self.cgImage!.bitsPerComponent, bytesPerRow: 0,
space: self.cgImage!.colorSpace!,
bitmapInfo: self.cgImage!.bitmapInfo.rawValue)!;
ctx.concatenate(transform)
if ( self.imageOrientation == .left ||
self.imageOrientation == .leftMirrored ||
self.imageOrientation == .right ||
self.imageOrientation == .rightMirrored ) {
ctx.draw(self.cgImage!, in: CGRect(x: 0.0,y: 0.0,width: self.size.height,height: self.size.width))
} else {
ctx.draw(self.cgImage!, in: CGRect(x: 0.0,y: 0.0,width: self.size.width,height: self.size.height))
}
// And now we just create a new UIImage from the drawing context and return it
return UIImage(cgImage: ctx.makeImage()!)
}
resize-a-uiimage-the-right-way explains some of the issues many code samples for doing this have, and has some code snippets to help deal with UIImages - the private helper method in UIImage+resize.m accepts a transform to allow rotation, so you'd just need to expose that as a public interface.
// 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;
}
This is the license from that file:
// Created by Trevor Harmon on 8/5/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.
Swift 4.2 version of RawMean's answer:
extension UIImage {
func rotated(byDegrees degree: Double) -> UIImage {
let radians = CGFloat(degree * .pi) / 180.0 as CGFloat
let rotatedSize = self.size
let scale = UIScreen.main.scale
UIGraphicsBeginImageContextWithOptions(rotatedSize, false, scale)
let bitmap = UIGraphicsGetCurrentContext()
bitmap?.translateBy(x: rotatedSize.width / 2, y: rotatedSize.height / 2)
bitmap?.rotate(by: radians)
bitmap?.scaleBy(x: 1.0, y: -1.0)
bitmap?.draw(
self.cgImage!,
in: CGRect.init(x: -self.size.width / 2, y: -self.size.height / 2 , width: self.size.width, height: self.size.height))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext() // this is needed
return newImage!
}
}
For Swift: Here is a simple extension to UIImage:
//ImageRotation.swift
import UIKit
extension UIImage {
public func imageRotatedByDegrees(degrees: CGFloat, flip: Bool) -> UIImage {
let radiansToDegrees: (CGFloat) -> CGFloat = {
return $0 * (180.0 / CGFloat(M_PI))
}
let degreesToRadians: (CGFloat) -> CGFloat = {
return $0 / 180.0 * CGFloat(M_PI)
}
// calculate the size of the rotated view's containing box for our drawing space
let rotatedViewBox = UIView(frame: CGRect(origin: CGPointZero, size: size))
let t = CGAffineTransformMakeRotation(degreesToRadians(degrees));
rotatedViewBox.transform = t
let rotatedSize = rotatedViewBox.frame.size
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize)
let bitmap = UIGraphicsGetCurrentContext()
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width / 2.0, rotatedSize.height / 2.0);
// // Rotate the image context
CGContextRotateCTM(bitmap, degreesToRadians(degrees));
// Now, draw the rotated/scaled image into the context
var yFlip: CGFloat
if(flip){
yFlip = CGFloat(-1.0)
} else {
yFlip = CGFloat(1.0)
}
CGContextScaleCTM(bitmap, yFlip, -1.0)
CGContextDrawImage(bitmap, CGRectMake(-size.width / 2, -size.height / 2, size.width, size.height), CGImage)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
}
(Source)
Use it with:
rotatedPhoto = rotatedPhoto?.imageRotatedByDegrees(90, flip: false)
The former will rotate an image and flip it if flip is set to true.
"tint uiimage grayscale" appears to be the appropriate Google-Fu for this one
straight away I get:
https://discussions.apple.com/message/8104516?messageID=8104516�
https://discussions.apple.com/thread/2751445?start=0&tstart=0
Here is a Swift extension to UIImage that rotates the image by any arbitrary angle. Use it like this: let rotatedImage = image.rotated(byDegrees: degree).
I used the Objective-C code in one of the other answers and removed a few lines that we incorrect (rotated box stuff) and turned it into an extension for UIImage.
extension UIImage {
func rotate(byDegrees degree: Double) -> UIImage {
let radians = CGFloat(degree*M_PI)/180.0 as CGFloat
let rotatedSize = self.size
let scale = UIScreen.mainScreen().scale
UIGraphicsBeginImageContextWithOptions(rotatedSize, false, scale)
let bitmap = UIGraphicsGetCurrentContext()
CGContextTranslateCTM(bitmap, rotatedSize.width / 2, rotatedSize.height / 2);
CGContextRotateCTM(bitmap, radians);
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2 , self.size.width, self.size.height), self.CGImage );
let newImage = UIGraphicsGetImageFromCurrentImageContext()
return newImage
}
}
I had trouble with ll of the above, including the approved answer. I converted Hardy's category back into a method since all i wanted was to rotate an image. Here's the code and usage:
- (UIImage *)imageRotatedByDegrees:(UIImage*)oldImage deg:(CGFloat)degrees{
// calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,oldImage.size.width, oldImage.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(degrees * M_PI / 180);
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
// // Rotate the image context
CGContextRotateCTM(bitmap, (degrees * M_PI / 180));
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-oldImage.size.width / 2, -oldImage.size.height / 2, oldImage.size.width, oldImage.size.height), [oldImage CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
And the usage:
UIImage *image2 = [self imageRotatedByDegrees:image deg:90];
Thanks Hardy!
Simple. Just change the image orientation flag.
UIImage *oldImage = [UIImage imageNamed:@"whatever.jpg"];
UIImageOrientation newOrientation;
switch (oldImage.imageOrientation) {
case UIImageOrientationUp:
newOrientation = UIImageOrientationLandscapeLeft;
break;
case UIImageOrientationLandscapeLeft:
newOrientation = UIImageOrientationDown;
break;
case UIImageOrientationDown:
newOrientation = UIImageOrientationLandscapeRight;
break;
case UIImageOrientationLandscapeRight:
newOrientation = UIImageOrientationUp;
break;
// you can also handle mirrored orientations similarly ...
}
UIImage *rotatedImage = [UIImage imageWithCGImage:oldImage.CGImage scale:1.0f orientation:newOrientation];
Minor change to the other answers that are based on Hardy Macia's code. There is no need to create a whole UIView object simply to calculate the bounding rectangle of the rotated image. Just apply a rotate transform to the image rectangle using CGRectApplyAffineTransform.
static CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;}
static CGFloat RadiansToDegrees(CGFloat radians) {return radians * 180/M_PI;}
- (CGSize)rotatedImageSize:(CGFloat)degrees
{
CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
CGRect originalImageRect = CGRectMake(0, 0, self.size.width, self.size.height);
CGRect rotatedImageRect = CGRectApplyAffineTransform(originalImageRect, t);
CGSize rotatedSize = rotatedImageRect.size;
return rotatedSize;
}
- (UIImage*)imageRotatedByDegrees:(CGFloat)degrees
{
// calculate the size of the rotated view's containing box for our drawing space
CGSize rotatedSize = [self rotatedImageSize:degrees];
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
// // Rotate the image context
CGContextRotateCTM(bitmap, DegreesToRadians(degrees));
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
As strange as this seems, the following code solved the problem for me:
+ (UIImage*)unrotateImage:(UIImage*)image {
CGSize size = image.size;
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0,0,size.width ,size.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Check out the simple and awesome code of Hardy Macia at: cutting-scaling-and-rotating-uiimages
Just call
UIImage *rotatedImage = [originalImage imageRotatedByDegrees:90.0];
Thanks Hardy Macia!
Header:
Since the link may die, here's the complete code
//
// UIImage-Extensions.h
//
// Created by Hardy Macia on 7/1/09.
// Copyright 2009 Catamount Software. All rights reserved.
//
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface UIImage (CS_Extensions)
- (UIImage *)imageAtRect:(CGRect)rect;
- (UIImage *)imageByScalingProportionallyToMinimumSize:(CGSize)targetSize;
- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize;
- (UIImage *)imageByScalingToSize:(CGSize)targetSize;
- (UIImage *)imageRotatedByRadians:(CGFloat)radians;
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees;
@end;
//
// UIImage-Extensions.m
//
// Created by Hardy Macia on 7/1/09.
// Copyright 2009 Catamount Software. All rights reserved.
//
#import "UIImage-Extensions.h"
CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};
CGFloat RadiansToDegrees(CGFloat radians) {return radians * 180/M_PI;};
@implementation UIImage (CS_Extensions)
-(UIImage *)imageAtRect:(CGRect)rect
{
CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], rect);
UIImage* subImage = [UIImage imageWithCGImage: imageRef];
CGImageRelease(imageRef);
return subImage;
}
- (UIImage *)imageByScalingProportionallyToMinimumSize:(CGSize)targetSize {
UIImage *sourceImage = self;
UIImage *newImage = nil;
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
CGFloat targetWidth = targetSize.width;
CGFloat targetHeight = targetSize.height;
CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
CGFloat widthFactor = targetWidth / width;
CGFloat heightFactor = targetHeight / height;
if (widthFactor > heightFactor)
scaleFactor = widthFactor;
else
scaleFactor = heightFactor;
scaledWidth = width * scaleFactor;
scaledHeight = height * scaleFactor;
// center the image
if (widthFactor > heightFactor) {
thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
} else if (widthFactor < heightFactor) {
thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
}
}
// this is actually the interesting part:
UIGraphicsBeginImageContext(targetSize);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumbnailPoint;
thumbnailRect.size.width = scaledWidth;
thumbnailRect.size.height = scaledHeight;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
if(newImage == nil) NSLog(@"could not scale image");
return newImage ;
}
- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize {
UIImage *sourceImage = self;
UIImage *newImage = nil;
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
CGFloat targetWidth = targetSize.width;
CGFloat targetHeight = targetSize.height;
CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
CGFloat widthFactor = targetWidth / width;
CGFloat heightFactor = targetHeight / height;
if (widthFactor < heightFactor)
scaleFactor = widthFactor;
else
scaleFactor = heightFactor;
scaledWidth = width * scaleFactor;
scaledHeight = height * scaleFactor;
// center the image
if (widthFactor < heightFactor) {
thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
} else if (widthFactor > heightFactor) {
thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
}
}
// this is actually the interesting part:
UIGraphicsBeginImageContext(targetSize);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumbnailPoint;
thumbnailRect.size.width = scaledWidth;
thumbnailRect.size.height = scaledHeight;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
if(newImage == nil) NSLog(@"could not scale image");
return newImage ;
}
- (UIImage *)imageByScalingToSize:(CGSize)targetSize {
UIImage *sourceImage = self;
UIImage *newImage = nil;
// CGSize imageSize = sourceImage.size;
// CGFloat width = imageSize.width;
// CGFloat height = imageSize.height;
CGFloat targetWidth = targetSize.width;
CGFloat targetHeight = targetSize.height;
// CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
// this is actually the interesting part:
UIGraphicsBeginImageContext(targetSize);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumbnailPoint;
thumbnailRect.size.width = scaledWidth;
thumbnailRect.size.height = scaledHeight;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
if(newImage == nil) NSLog(@"could not scale image");
return newImage ;
}
- (UIImage *)imageRotatedByRadians:(CGFloat)radians
{
return [self imageRotatedByDegrees:RadiansToDegrees(radians)];
}
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees
{
// calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
[rotatedViewBox release];
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
// // Rotate the image context
CGContextRotateCTM(bitmap, DegreesToRadians(degrees));
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
@end;
Rotate Image by 90 degree (clockwise/anti-clockwise direction)
Function call -
UIImage *rotatedImage = [self rotateImage:originalImage clockwise:YES];
Implementation:
- (UIImage*)rotateImage:(UIImage*)sourceImage clockwise:(BOOL)clockwise
{
CGSize size = sourceImage.size;
UIGraphicsBeginImageContext(CGSizeMake(size.height, size.width));
[[UIImage imageWithCGImage:[sourceImage CGImage]
scale:1.0
orientation:clockwise ? UIImageOrientationRight : UIImageOrientationLeft]
drawInRect:CGRectMake(0,0,size.height ,size.width)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
There is a extremely efficient UIImage category named NYXImagesKit. It uses vDSP, CoreImage and vImage to be as fast as possible. It has a UIImage+Rotating category that saved my day :)
Source: Stackoverflow.com