NSImage rotation using block code blurry on non-retina - macos

Question

I am using the following function to rotate an NSImage. It uses block code in order to render properly on retina. The problem now is that it renders blurry on non-retina screens.
I tried checking for a retina display [NSWindow backingScaleFactor] and then using a non-block method on non-retina displays, but the is a case in which it doesn't work - if the user has a retina Mac but is displaying to an external non-retina display, the check backingScaleFactor reports a retina screen. I then found this document on Apple's developer site:
APIs for Supporting High Resolution
https://developer.apple.com/library/mac/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/APIs/APIs.html
But it's frankly inscrutable. How can the following function be modified to not blur on non-retina displays?
- (NSImage *)imageRotatedByDegrees:(CGFloat)degrees {
// calculate the bounds for the rotated image
NSRect imageBounds = {NSZeroPoint, [self size]};
NSBezierPath *boundsPath = [NSBezierPath bezierPathWithRect:imageBounds];
NSAffineTransform *transform = [NSAffineTransform transform];
[transform rotateByDegrees:degrees];
[boundsPath transformUsingAffineTransform:transform];
NSRect rotatedBounds = {NSZeroPoint, [boundsPath bounds].size};
// center the image within the rotated bounds
imageBounds.origin.x = NSMidX(rotatedBounds) - (NSWidth (imageBounds) / 2);
imageBounds.origin.y = NSMidY(rotatedBounds) - (NSHeight (imageBounds) / 2);
NSImage *rotatedImage = [NSImage imageWithSize:rotatedBounds.size flipped:NO drawingHandler:^BOOL (NSRect dstRect) {
// set up the rotation transform
NSAffineTransform *transform=[NSAffineTransform transform];
[transform translateXBy:+(NSWidth(rotatedBounds) / 2) yBy:+(NSHeight(rotatedBounds) / 2)];
[transform rotateByDegrees:degrees];
[transform translateXBy:-(NSWidth(rotatedBounds) / 2) yBy:-(NSHeight(rotatedBounds) / 2)];
// draw the original image, rotated, into the new image
[transform concat];
[self drawInRect:imageBounds fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
return YES;
}];
return rotatedImage;
}
Thanks

Answer 1

Try this
(NSImage*)rotateImagedByDegrees:(CGFloat)degrees Image:(NSImage *)sourceImage
{
NSImage *image = sourceImage;
if (degrees == 0)
{
return image;
}
else
{
NSRect imageBounds = {NSZeroPoint, [sourceImage size]};
NSSize rotatedSize = NSMakeSize(sourceImage.size.height, sourceImage.size.width) ;
NSImage* rotatedImage = [[NSImage alloc] initWithSize:rotatedSize] ;
NSBezierPath* boundsPath = [NSBezierPath bezierPathWithRect:imageBounds];
NSAffineTransform* transform = [NSAffineTransform transform];
[transform rotateByDegrees:-1.0 * degrees];
[boundsPath transformUsingAffineTransform:transform];
NSRect rotatedBounds = {NSZeroPoint, [boundsPath bounds].size};
imageBounds.origin.x = NSMidX(rotatedBounds) - (NSWidth(imageBounds) / 2);
imageBounds.origin.y = NSMidY(rotatedBounds) - (NSHeight(imageBounds) / 2);
rotatedImage = [NSImage imageWithSize:rotatedBounds.size flipped:NO drawingHandler:NO];
NSAffineTransform* transform1 = [NSAffineTransform transform];
[transform1 translateXBy:+(NSWidth(rotatedBounds) / 2) yBy:+(NSHeight(rotatedBounds) / 2)];
[transform1 rotateByDegrees:-1.0 * degrees];
[transform1 translateXBy:-(NSWidth(rotatedBounds) / 2) yBy:-(NSHeight(rotatedBounds) / 2)];
[rotatedImage lockFocus] ;
[transform1 concat] ;
[sourceImage drawInRect:imageBounds
fromRect:NSMakeRect(0.0, 0.0, [sourceImage size].width, [sourceImage size].height)
operation:NSCompositeSourceOver fraction:1.0];
[rotatedImage unlockFocus] ;
return rotatedImage;
}
}