UIImage iPhone Rotate 37.8 degrees - iphone

Question

After I load an image from the device, I need to rotate it 37.8 degrees then display it on a View.
Is there an function in Objective-C that can do the image rotation?
Ian

Answer 1

To rotate the view:
imageView.transform = CGAffineTransformMakeRotation(37.8°);
To rotate the image,
Calculate the width and height will be occupied by the image after rotation.
Create a CGContext by UIGraphicsBeginImageContext.
CGContextRotateCTM(UIGraphicsGetCurrentContext(), 37.8°);
[yourImage drawAtPoint:...];
UIGraphicsGetImageFromCurrentImageContext(); and use this image instead.
Release the context.

Answer 2

Yes, see my answer to this question: Question about rotating a slider
To convert degrees to radians (for the positionInRadians arg) use this function:
CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};

Answer 3

To rotate the image, try this:
-(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);
}
This method allows you to rotate an image an arbitrary amount:
- (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;
}
See this link for more information.