Escribí una función de generación de gradiente como una categoría en SKTexture. Funciona bien en pantallas de 1x, pero la retina hace que la textura sea demasiado grande, doble ancho y doble altura, es decir, escala incorrecta. He estado tratando de hacerlo bien cambiando entre píxeles y puntos, pero no puedo hacerlo bien. ¿Puede alguien ayudarme por favor?

+(SKTexture*)gradientWithSize:(const CGSize)SIZE colors:(NSArray*)colors {
    // Hopefully this function would be platform independent one day.

    // Correct way to find scale?
    DLog(@"backingScaleFactor: %f", [[NSScreen mainScreen] backingScaleFactor]);
    const CGFloat SCALE = [[NSScreen mainScreen] backingScaleFactor];
    //const size_t WIDTH_PIXELS = SIZE.width * SCALE;
    //const size_t HEIGHT_PIXELS = SIZE.height * SCALE;
    CGContextRef cgcontextref = MyCreateBitmapContext(SIZE.width, SIZE.height, SCALE);
    NSAssert(cgcontextref != NULL, @"Failed creating context!");
    //  CGBitmapContextCreate(
    //                                                    NULL, // let the OS handle the memory
    //                                                    WIDTH_PIXELS,
    //                                                    HEIGHT_PIXELS,

    CAGradientLayer* gradient = CAGradientLayer.layer;
    //gradient.contentsScale = SCALE;
    gradient.frame = CGRectMake(0, 0, SIZE.width, SIZE.height);

    NSMutableArray* convertedcolors = [NSMutableArray array];
    for (SKColor* skcolor in colors) {
        [convertedcolors addObject:(id)skcolor.CGColor];
    }
    gradient.colors = convertedcolors;
    [gradient renderInContext:cgcontextref];

    CGImageRef imageref = CGBitmapContextCreateImage(cgcontextref);
    DLog(@"imageref pixel size: %zu %zu", CGImageGetWidth(imageref), CGImageGetHeight(imageref));

    SKTexture* texture1 = [SKTexture textureWithCGImage:imageref];
    DLog(@"size of gradient texture: %@", NSStringFromSize(texture1.size));

    CGImageRelease(imageref);

    CGContextRelease(cgcontextref);

    return texture1;
}
CGContextRef MyCreateBitmapContext(const size_t POINTS_W, const size_t POINTS_H, const CGFloat SCALE) {
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    void *          bitmapData;
    //int             bitmapByteCount;
    size_t             bitmapBytesPerRow;

    const size_t PIXELS_W = POINTS_W * SCALE;
    const size_t PIXELS_H = POINTS_H * SCALE;

    bitmapBytesPerRow   = (PIXELS_W * 4);// 1
    //bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

    colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);// 2
    bitmapData = NULL;

#define kBitmapInfo     kCGImageAlphaPremultipliedLast
    //#define kBitmapInfo       kCGImageAlphaPremultipliedFirst
    //#define kBitmapInfo       kCGImageAlphaNoneSkipFirst
    // According to http://stackoverflow.com/a/18921840/129202 it should be safe to just cast
    CGBitmapInfo bitmapinfo = (CGBitmapInfo)kBitmapInfo; //kCGImageAlphaNoneSkipFirst; //0; //kCGBitmapAlphaInfoMask; //kCGImageAlphaNone; //kCGImageAlphaNoneSkipFirst;
    context = CGBitmapContextCreate (bitmapData,// 4
                                     PIXELS_W,
                                     PIXELS_H,
                                     8,      // bits per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     bitmapinfo
                                     );
    if (context == NULL) {
        free (bitmapData);// 5
        fprintf (stderr, "Context not created!");
        return NULL;
    }
    CGColorSpaceRelease( colorSpace );// 6

    // TEST!!
//  CGContextClipToRect(context, CGRectMake(0, 0, POINTS_W, POINTS_H));
    CGContextClipToRect(context, CGRectMake(0, 0, PIXELS_W, PIXELS_H));
    CGContextScaleCTM(context, SCALE, SCALE);

    return context;// 7
}

Así que, para resumir, espero llamar+(SKTexture*)gradientWithSize:(const CGSize)SIZE colors:(NSArray*)colors utilizando puntos para TAMAÑO.