Core graphics drawing stretches when orientation changes - objective-c

Question

I am making an app that allows you to draw, and it is working well in portrait mode. However, when I rotate the screen, the drawn image becomes distorted (squashed and stretched). What would I need to do to make it retain the image's dimensions even though the UIImageView has changed its dimensions?
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.view]; // first point touched
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view]; // second point touched (to be connected to first point)
// initialize the UIImageView that will be drawn on
UIGraphicsBeginImageContext(self.view.frame.size);
//UIGraphicsBeginImageContextWithOptions(self.view.frame.size, NO, 0.0); // use this instead of previous line to make smoother drawings
if (!erasing) // choose tempDrawImage if not erasing
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
else // choose mainImage if erasing
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
// draw a line with CGContextAddLineToPoint from lastPoint to currentPoint
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
if (!erasing) { // color selected
// set brush size, opacity, and stroke color
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
// draw the path
CGContextStrokePath(UIGraphicsGetCurrentContext());
// draw on the tempDrawImage UIImageView
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tempDrawImage setAlpha:opacity];
}
else { // eraser selected
// set brush size
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeClear);
// draw the path
CGContextStrokePath(UIGraphicsGetCurrentContext());
// draw on the tempDrawImage UIImageView
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
//[self.mainImage setAlpha:1.0];
}
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
// if screen was not swiped (i.e. the screen was only tapped), draw a single point
if(!mouseSwiped) {
UIGraphicsBeginImageContext(self.view.frame.size);
//UIGraphicsBeginImageContextWithOptions(self.view.frame.size, NO, 0.0); // use this instead of previous line to make smoother drawings
if (!erasing) {
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, opacity);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
}
else {
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeClear);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
}
UIGraphicsEndImageContext();
}
///////BRUSH STROKE IS DONE; BEGIN UIIMAGEVIEW MERGE//////
if (!erasing) {
// initialize mainImage (for merge)
UIGraphicsBeginImageContext(self.mainImage.frame.size);
// merge tempDrawImage with mainImage
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height) blendMode:kCGBlendModeNormal alpha:opacity];
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
// clear tempDrawImage
self.tempDrawImage.image = nil;
}
UIGraphicsEndImageContext();
}