问题
I want to rotate an UIImage (not UIImageView) in custom degree I followed this post but it didn't work for me.
Anyone can help? Thanks.
UPDATE: The code below does some of the job, but I lose some of the image after rotating it:
What should I change to get it right? (btw the yellow color in the screenshots is my UIImageView bg)
- (UIImage *) rotate: (UIImage *) image
{
double angle = 20;
CGSize s = {image.size.width, image.size.height};
UIGraphicsBeginImageContext(s);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(ctx, 0,image.size.height);
CGContextScaleCTM(ctx, 1.0, -1.0);
CGContextRotateCTM(ctx, 2*M_PI*angle/360);
CGContextDrawImage(ctx,CGRectMake(0,0,image.size.width, image.size.height),image.CGImage);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
回答1:
This method return you image on your angle of rotate
#pragma mark -
#pragma mark Rotate Image
- (UIImage *)scaleAndRotateImage:(UIImage *)image {
CGImageRef imgRef = image.CGImage;
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
CGFloat boundHeight;
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); //use angle/360 *MPI
UIGraphicsBeginImageContext(bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextConcatCTM(context, transform);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imgRef);
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return imageCopy;
}
回答2:
- (UIImage *)rotate:(UIImage *)image radians:(float)rads
{
float newSide = MAX([image size].width, [image size].height);
CGSize size = CGSizeMake(newSide, newSide);
UIGraphicsBeginImageContext(size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(ctx, newSide/2, newSide/2);
CGContextRotateCTM(ctx, rads);
CGContextDrawImage(UIGraphicsGetCurrentContext(),CGRectMake(-[image size].width/2,-[image size].height/2,size.width, size.height),image.CGImage);
//CGContextTranslateCTM(ctx, [image size].width/2, [image size].height/2);
UIImage *i = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return i;
}
this function rotates any image on its center, but the image becomes a square so I would suggest referencing the image center when drawing it after this function.
回答3:
You need to address two things to make this work.
- You are rotating about the bottom corner of the image instead of the centre
- The bounding rectangle of the resulting image needs to be larger now the image is rotated for it to fit in.
To solve the rotation about the centre, first perform a translate to the centre, then rotate, then translate back.
CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformTranslate(transform, boundingRect.size.width/2, boundingRect.size.height/2);
transform = CGAffineTransformRotate(transform, angle);
transform = CGAffineTransformScale(transform, 1.0, -1.0);
CGContextConcatCTM(context, transform);
// Draw the image into the context
CGContextDrawImage(context, CGRectMake(-imageView.image.size.width/2, -imageView.image.size.height/2, imageView.image.size.width, imageView.image.size.height), imageView.image.CGImage);
// Get an image from the context
rotatedImage = [UIImage imageWithCGImage: CGBitmapContextCreateImage(context)];
To calculate the size of the bounding rectangle you'd need to fit the new rotated image into use this:
- (CGRect) getBoundingRectAfterRotation: (CGRect) rectangle byAngle: (CGFloat) angleOfRotation {
// Calculate the width and height of the bounding rectangle using basic trig
CGFloat newWidth = rectangle.size.width * fabs(cosf(angleOfRotation)) + rectangle.size.height * fabs(sinf(angleOfRotation));
CGFloat newHeight = rectangle.size.height * fabs(cosf(angleOfRotation)) + rectangle.size.width * fabs(sinf(angleOfRotation));
// Calculate the position of the origin
CGFloat newX = rectangle.origin.x + ((rectangle.size.width - newWidth) / 2);
CGFloat newY = rectangle.origin.y + ((rectangle.size.height - newHeight) / 2);
// Return the rectangle
return CGRectMake(newX, newY, newWidth, newHeight);
}
You can find these techniques in my previous posts and answers here:
Creating a UIImage from a rotated UIImageView
and here:
Saving 2 UIImages
Hope this helps,
Dave
回答4:
for rotate image.. you can use this IBAction ... for each and every button click, the image will be rotate by 90 degree...
-(IBAction)rotateImageClick:(id)sender{
UIImage *image2=[[UIImage alloc]init];
image2 = [self imageRotatedByDegrees:self.roateImageView.image deg:(90)]; //Angle by 90 degree
self.roateImageView.image = image2;
imgData= UIImageJPEGRepresentation(image2,0.9f);
}
for rotating image u only have to pass UIimage and rotating degrees for the following method
- (UIImage *)imageRotatedByDegrees:(UIImage*)oldImage deg:(CGFloat)degrees
//------------------------------------------------------------------------
#pragma mark - imageRotatedByDegrees Method
- (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;
}
I think this link will be help.......! Rotate Original Image by clicking button in Objective C
http://adrianmobileapplication.blogspot.com/2015/03/rotate-original-image-by-clicking.html
回答5:
You have to do some thing like this
YourContainer.transform = CGAffineTransformMakeRotation( 270.0/180*M_PI );
I think rest of the thing you can figured out..
来源：https://stackoverflow.com/questions/5102474/rotate-uiimage-custom-degree