iOS-Drawing on an image with CGContextRef

Question

I'm trying to draw on an image using CGContextRef with the following piece of code:

UIGraphicsBeginImageContextWithOptions(size, false, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
// After getting the context i pass it to a C++ backend by an appropriate wrapper and do some drawing operations.

Then I try to get the image from context with the following piece of code:

CGImageRef image = [UIGraphicsGetImageFromCurrentImageContext() CGImage];

But this returns an image with size (0,0).

I tried to get the image with:

CGImageRef image = CGBitmapContextCreateImage(context);

This returns a blank image with the original size multiplied by 3 for both width and height.

Any suggestions?