I wrote a gradient generating function as a category on SKTexture. It works well on 1x screens but retina renders the texture too big, double width and double height ie wrong scale. I have been trying to get it right by changing between pixels and points, but can't get it right. Can someone help me please?
+(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
}
So, to some sum it up, I expect to call +(SKTexture*)gradientWithSize:(const CGSize)SIZE colors:(NSArray*)colors
using points for SIZE.