Question

How does one serialize a CGContext that contains a modified CGMutablePathRef?

I currently save the context into png representation and serialize this, but it is causing issues with retina display.

I would like to avoid serializing a retina version and resizing it at runtime as this would be inefficient.

Answer 1

If you are just stroking or filling a single path, you can wrap it in a UIBezierPath, which conforms to the NSCoding protocol, and then you can serialize the UIBezierPath:

UIBezierPath *uiPath = [UIBezierPath bezierPathWithCGPath:cgPath];
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:uiPath];

Then you can write data to a file or your database or whatever. Later you can convert data back to a UIBezierPath and then a CGPath:

UIBezierPath *uiPath = [NSKeyedUnarchiver unarchiveObjectWithData:data];
CGPathRef cgPath = uiPath.CGPath;

If you are drawing something more complex than a single path, the easiest way to serialize your drawing in a scalable (vector) format is to draw to a CGPDFContext instead of a CGBitmapContext. A CGPDFContext records your drawing commands to a PDF. Later, you can create a CGPDFDocument for the PDF, and use that to draw the PDF to your bitmap context. Read the PDF Document Creation, Viewing, and Transforming chapter of the * Quartz 2D Programming Guide* for details.