I have a UIImageView and I am applying a rotation transform using CGAffineTransformMakeRotation. This does not only rotate the image but scales it as well.
What is the correct way to rotate a UIImageView and retain the size/scale of the image?
I tried setting
self.image.contentMode = UIViewContentModeCenter;
self.image.autoresizingMask = UIViewAutoresizingNone;
and it doesn't seem to help.
try the below method
-(UIImage*)rotateImage:(UIImage*)img forAngle:(CGFloat)radian {
UIView *rotatedViewBox = [[UIView alloc]initWithFrame:CGRectMake(0, 0, img.size.width, img.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(radian);
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, rotatedSize.width, rotatedSize.height);
CGContextRotateCTM(context, radian);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(-img.size.width, -img.size.height, img.size.width, img.size.height), img.CGImage);
UIImage *returnImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return returnImg;
}
Related
I need to take a UIImage and to add a semi-transparent layer in order to produce a new UIImage. I think I'm getting close but something is still wrong. Here's my code:
- (UIImage*) addLayerTo:(UIImage*)source
{
CGSize size = [source size];
UIGraphicsBeginImageContext(size);
CGRect rect = CGRectMake(0, 0, size.width, size.height);
[source drawInRect:rect blendMode:kCGBlendModeNormal alpha:0.18];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 0.2, 0.5, 0.1, 0.18);
CGContextFillRect(context, rect);
UIImage *testImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return testImg;
}
You forgot to draw the current image you want to blend with source image in current context.
- (UIImage*) addLayerTo:(UIImage*)source
{
CGSize size = [source size];
UIGraphicsBeginImageContext(size, NO, [UIScreen mainScreen].scale); // Use this image context initialiser instead
CGRect rect = CGRectMake(0, 0, size.width, size.height);
[self drawInRect: rect] // Draw the current image in context
[source drawInRect:rect blendMode:kCGBlendModeNormal alpha:0.18]; // Blend with other image
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 0.2, 0.5, 0.1, 0.18);
CGContextFillRect(context, rect);
UIImage *testImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return testImg;
}
- (UIImage*) addLayerTo:(UIImage*)source
{
CGSize size = [source size];
// create context with UIScrean scale
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
// get new context
CGContextRef ctx1 = UIGraphicsGetCurrentContext();
// draw view
CGContextDrawImage(ctx1, CGRectMake(0.0f, 0.0f, size.width, size.height), source.CGImage);
// set fill color
UIColor *fillColor = [UIColor purpleColor];
// fill with it
CGContextSetFillColorWithColor(ctx1, fillColor.CGColor);
CGContextFillRect(ctx1, CGRectMake(0, 0, size.width, size.height));
// create new image
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
// end context
UIGraphicsEndImageContext();
return outputImage;
}
Hi in my iOS application I want to rotate the UIImage data in 90 Degrees.
I used the below code for 180 degree rotation - and it works fine.
- (UIImage*)upsideDownBunny:(UIImage *)img {
CGSize imgSize = [img size];
UIGraphicsBeginImageContext(imgSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRotateCTM(context, M_PI);
CGContextTranslateCTM(context, -imgSize.width, -imgSize.height);
[img drawInRect:CGRectMake(0, 0, imgSize.width, imgSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
But when I try to rotate in 90 degree it is not working - please correct me
- (UIImage *)upsideDownBunny:(UIImage *)img {
CGSize imgSize = [img size];
UIGraphicsBeginImageContext(imgSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRotateCTM(context, M_PI_2);
CGContextTranslateCTM(context, -imgSize.width, -imgSize.height);
[img drawInRect:CGRectMake(0, 0, imgSize.width, imgSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Try this...
UIImage * LandscapeImage = [UIImage imageNamed: imgname];
UIImage * PortraitImage = [[UIImage alloc] initWithCGImage: LandscapeImage.CGImage
scale: 1.0
orientation: UIImageOrientationLeft];
hope this helps you!
Try this
- (UIImage *)upsideDownBunny:(UIImage *)image {
// Rotate in degrees
CGFloat degrees = M_PI_2;
// Calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0, 0, image.size.width, image.size.height)];
CGAffineTransform transform = CGAffineTransformMakeRotation(degrees);
rotatedViewBox.transform = transform;
CGSize rotatedSize = rotatedViewBox.frame.size;
// Create image context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef context = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image.
CGContextTranslateCTM(context, rotatedSize.width * 0.5f, rotatedSize.height * 0.5f);
// Rotate the image context
CGContextRotateCTM(context, degrees);
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(-image.size.width * 0.5f, -image.size.height * 0.5f, image.size.width, image.size.height), [image CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
The problem is your context is being rotated around (0,0) which is the top left corner and after 90 degrees rotate it will go out of bounds. So you need to move the origin of the context to middle.
In the code below I'm adding a small image to a large image. I need to be able to apply a transform to the small image. Right now something weird is going on, for example if I pass in a transform of CGAffineTransformMakeRotation(M_PI_2), the newImage is not rotated in place but rather drawn somewhere off screen. How can I fix this?
+ (UIImage*)addToImage:(UIImage *)baseImage newImage:(UIImage*)newImage atPoint:(CGPoint)point transform:(CGAffineTransform)transform {
UIGraphicsBeginImageContextWithOptions(baseImage.size, NO, 1);
CGContextRef context = UIGraphicsGetCurrentContext();
[baseImage drawInRect:CGRectMake(0, 0, baseImage.size.width, baseImage.size.height)];
CGRect newRect = CGRectMake(point.x,
point.y,
newImage.size.width,
newImage.size.height);
CGContextConcatCTM(context, transform);
[newImage drawInRect:newRect];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
Note that I only want to apply the transform to newImage, not baseImage.
Seems like you just forgot to translate the origin of the context before and after the rotation. Here, try this:
- (UIImage*)addToImage:(UIImage *)baseImage newImage:(UIImage*)newImage atPoint:(CGPoint)point transform:(CGAffineTransform)transform {
UIGraphicsBeginImageContextWithOptions(baseImage.size, NO, [[UIScreen mainScreen] scale]);
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect baseRect = CGRectMake(0, 0, baseImage.size.width, baseImage.size.height);
[baseImage drawInRect:baseRect];
CGRect newRect = CGRectMake(point.x, point.y, newImage.size.width, newImage.size.height);
CGContextTranslateCTM(context, point.x, point.y);
CGContextConcatCTM(context, transform);
CGContextTranslateCTM(context, -point.x, -point.y);
[newImage drawInRect:newRect];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
EDIT:
If you want to rotate the image around its center, add the halves of the image's sides to the corresponding translation values:
float xTranslation = point.x+newRect.size.width/2;
float yTranslation = point.y+newRect.size.height/2;
CGContextTranslateCTM(context, xTranslation, yTranslation);
CGContextConcatCTM(context, transform);
CGContextTranslateCTM(context, -xTranslation, -yTranslation);
How to draw smaller image than size of context without using CGAffineTransform?
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
// center image
CGContextTranslateCTM(context, placement.origin.x, placement.origin.y);
[imageView.layer renderInContext:context];
The problem is that if imageView.image.size is bigger than size it will be drawn centered, but cut at borders (bigger image than drawing area). I want the image to fit, so would like to decrease size of imageView.image.size. Is there any way to achieve this using renderInContext?
Via [imageView.layer renderInContext:context]; you can't change the size (or i didn't find a way). The only option to do so, is to create now image with drawImage (on requested size), allocate new UIImageView and draw its layer.
UIImage *resizedImage = [self createNewImageFrom:currentImage withSize:size];
UIImageView *imageView = [[UIImageView alloc] initWithImage:resizedImage];
// ...
[imageView.layer renderInContext:context];
- (UIImage*)createNewImageFrom:(UIImage*)image withSize:(CGSize)size {
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0.0f, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height), image.CGImage);
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}
Why do you want to do this without transforming the context? It's the exact right tool for the job!
The simplest way here would be to call CGContextScaleCTM to apply a scale factor to the context. That scale factor will effect all drawing to the context, including the call to -renderIntoContext:.
this is version for scaled size, just replace scale with size.width and size.height for any target size.
for UIView:
-(UIImage*)convertViewToImage:(UIView*)v withScale:(float)scale{
//create bitmap context with scaled size
CGSize s = v.bounds.size;
s.width *= scale;
s.height *= scale;
UIGraphicsBeginImageContextWithOptions(s, NO, [UIScreen mainScreen].scale);
//scale CTM to render and resotre CTM
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextScaleCTM(context, scale, scale);
[v.layer renderInContext: context];
CGContextRestoreGState(context);
UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
for UIScrollView
-(UIImage*)convertScrollContentToImage:(UIScrollView*)sv withScale:(float)scale{
//create bitmap context with scaled size
CGSize s = sv.contentSize;
s.width *= scale;
s.height *= scale;
UIGraphicsBeginImageContextWithOptions(s, NO, [UIScreen mainScreen].scale);
{
//set scroll.frame.size to contentSize, and contentOffset to 0
CGPoint savedContentOffset = sv.contentOffset;
CGRect savedFrame = sv.frame;
sv.contentOffset = CGPointZero;
sv.frame = CGRectMake(0, 0, sv.contentSize.width, sv.contentSize.height);
//scale CTM to render and resotre CTM
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextScaleCTM(context, scale, scale);
[sv.layer renderInContext: context];
CGContextRestoreGState(context);
//set scroll.frame.size and ContentOffset back
sv.contentOffset = savedContentOffset;
sv.frame = savedFrame;
}
UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
I want to rotate a UIImageView with the press of a button. I am using this code:
#import "UIImage-Extensions.h"
UIImage *rotatedImage = [SplashItGroupPicker.image imageRotatedByDegrees:360/arrayCount];
SplashItGroupPicker.image = rotatedImage;
and in "UIImage-Extensions.h" i have:
#interface UIImage (CS_Extensions)
- (UIImage *)imageRotatedByRadians:(CGFloat)radians;
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees;
and in the .m:
- (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;
// 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;
}
...the rotation works fine, but when the image is rotated, the image also gets smaller and I can't understand why. Any ideas?
Here's a guess, is this only happening on Retina screens? Whenever saving a UIImage from a graphics context, you need to make sure the scale is correct. This is how I have done it:
CGFloat scale = [[UIScreen mainScreen] scale];
CGSize size = CGSizeMake(rotatedViewBox.frame.size.width * scale, rotatedViewBox.frame.size.height * scale);
UIGraphicsBeginImageContext( size );
/* Do your image manipulations here */
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// overwrite the image with one that has the correct scale set
newImage = [UIImage imageWithCGImage:newImage.CGImage scale:scale orientation:newImage.imageOrientation];
Using Kekoa's snippet (thanks a ton), I was able to get a working rotateImage function that works on retina devices based on Apples rotateImage code:
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees {
CGFloat radians = DegreesToRadians(degrees);
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0, self.size.width, self.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(radians);
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, [[UIScreen mainScreen] scale]);
CGContextRef 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 );
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
There is no need to UIGraphicsGetImageFromCurrentImageContext. its a way to get screenshot of desired portion of mainscreen. so the result image quality affected. the only way to get Rotated Image is...
first rotate your image view by(if you want to show rotated view)
[mainImgV setTransform:CGAffineTransformRotate(mainImgV.transform, M_PI)];
it will rotate your imageview.
now you will take this rotated image by these lines.(you can call these lines without rotate imgaeview also.)
CGImageRef cgRef = mainImgV.image.CGImage;
newImage = [[UIImage alloc] initWithCGImage:cgRef scale:1.0 orientation:UIImageOrientationDown];
there is no need to save or take screenshot or compromise bad quality image. just enjoy coding.