Anti-aliasing UIimage looks blurred or jagged - iphone

Question

i want to draw 12 images in a circle representing the watch numbers, i have read all topics on stackoverflow regarding images with transparent border but it's not working in my case
-(UIImage *)addImageNumber_:(UIImage *)img {
int w = img.size.width;
int h = img.size.height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1);
CGContextSetShouldAntialias(context,YES);
CGContextSetAllowsAntialiasing( context ,YES );
CGAffineTransform transform;
for (int x=0; x<=11; x++) {
UIImage *timg1 = [UIImage imageNamed:#"2.png"];
CGRect imageRect = CGRectMake(0, 0, timg1.size.width+2, timg1.size.height+2);
UIGraphicsBeginImageContext(imageRect.size);
[timg1 drawInRect:CGRectMake(1,1,timg1.size.width,timg1.size.height)];
timg1 = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
transform = CGAffineTransformIdentity;
CGContextDrawImage(context, CGRectMake((w-26)/2, 0, 26, 30), timg1.CGImage);
transform = CGAffineTransformConcat(transform, CGAffineTransformMakeTranslation(-w/2, -w/2));
transform = CGAffineTransformConcat(transform, CGAffineTransformMakeRotation(radians(30)));
transform = CGAffineTransformConcat(transform, CGAffineTransformMakeTranslation(w/2, w/2));
CGContextConcatCTM(context, transform);
}
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked];
}
UIViewEdgeAntialiasing = YES;
UIImage *img = [UIImage imageNamed:#"test.png"];
UIImage *img2 = [self addImageNumber_:img ];
R1.image = img2;
[self.view addSubview:R1];
test img is the background of the watch , 2.png is a transparent png with transparent borders
numbers at 12'o clock and 6'o clock looks ok because they are not rotated the rest are jaggy

Answer 1

Never say UIGraphicsBeginImageContext(imageRect.size). Say UIGraphicsBeginImageContextWithOptions(imageRect.size, NO, 0). That way, on a double-resolution screen, you'll get a double-resolution graphics context.
You could even try a resolution value of 4 to increase the resolution even further.
Of course, the fact that you're starting with a pre-drawn image of a "2" might limit your resolution; you can't make a silk purse out of a sow's ear. You could be a lot better off drawing the "2" from scratch as a string.

Answer 2

try
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);

Answer 3

Swift 3:
context!.interpolationQuality = .high