CoreGraphics for retina display

I am using the following code to perform some manipulations on the image that I loaded, but I find that the display becomes blurry when it is on the retina display

- (UIImage*)createImageSection:(UIImage*)image section:(CGRect)section

{
float originalWidth = image.size.width ;
float originalHeight = image.size.height ;
int w = originalWidth * section.size.width;
int h = originalHeight * section.size.height;

CGContextRef ctx = CGBitmapContextCreate(nil, w, h, 8, w * 8,CGImageGetColorSpace([image CGImage]), kCGImageAlphaPremultipliedLast);
CGContextClearRect(ctx, CGRectMake(0, 0, originalWidth * section.size.width, originalHeight * section.size.height)); // w + h before
CGContextTranslateCTM(ctx, (float)-originalWidth * section.origin.x, (float)-originalHeight * section.origin.y);
CGContextDrawImage(ctx, CGRectMake(0, 0, originalWidth, originalHeight), [image CGImage]);
CGImageRef cgImage = CGBitmapContextCreateImage(ctx);
UIImage* resultImage = [[UIImage alloc] initWithCGImage:cgImage];

CGContextRelease(ctx);
CGImageRelease(cgImage);

return resultImage;
}

How do I change this to make it retina compatible.

Thanks in advance for your help

Best, DV