NSImage retina detection category

NSImage+Retina.h

//
//  NSImage+Retina.h
//
//  Created by Levi Nunnink on 3/11/14.
//

#import <Cocoa/Cocoa.h>

@interface NSImage (Retina)

- (BOOL)hasRetina;
- (float)backingScaleForRepresentation:(NSBitmapImageRep*)rep;
- (NSBitmapImageRep*)representationForBackingScale:(float)backingScale;
- (NSBitmapImageRep*)retinaRep;
- (NSBitmapImageRep*)standardRep;
- (NSImage*)retinaImage;
- (NSImage*)standardImage;

@end

NSImage+Retina.m

//
//  NSImage+Retina.m
//
//  Created by Levi Nunnink on 3/11/14.
//

#import "NSImage+Retina.h"

@implementation NSImage (Retina)

- (BOOL)hasRetina
{
    return [self representationForBackingScale:2.0] != nil;
}

- (float)backingScaleForRepresentation:(NSBitmapImageRep*)rep
{
    return rep.pixelsWide / rep.size.width;
}

- (NSBitmapImageRep*)representationForBackingScale:(float)backingScale
{
    NSInteger backingScaleRounded = roundf(backingScale * 100);
    for(NSBitmapImageRep *rep in [self representations]){
        NSInteger repBackingScaleRounded = roundf((rep.pixelsWide / rep.size.width) * 100);
        if (backingScaleRounded == repBackingScaleRounded) {
            return rep;
        }
    }
    return nil;
}

- (NSBitmapImageRep*)retinaRep
{
    return [self representationForBackingScale:2.0];
}

- (NSBitmapImageRep*)standardRep
{
    return [self representationForBackingScale:1.0];
}

- (NSImage*)retinaImage
{
    NSBitmapImageRep *rep = [self representationForBackingScale:2.0];
    
    if (rep) {
        NSImage *img = [[NSImage alloc] initWithSize:rep.size];
        [img addRepresentation:rep];
        return img;
    }
    
    return nil;
}

- (NSImage*)standardImage
{
    NSBitmapImageRep *rep = [self representationForBackingScale:1.0];
    
    if (rep) {
        NSImage *img = [[NSImage alloc] initWithSize:rep.size];
        [img addRepresentation:rep];
        return img;
    }
    
    return nil;
}

@end