Drawing a PDF Right-Side-Up in CGContext
- by Carter Allen
I'm overriding the drawRect: method in a custom UIView, and I'm doing some custom drawing. All was going well, until I needed to draw a PDF resource (a vector glyph, to be precise) into the context. First I retrieve the PDF from a file:
NSURL *pdfURL = [NSURL fileURLWithPath:[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"CardKit.bundle/A.pdf"]];
CGPDFDocumentRef pdfDoc = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
CGPDFPageRef pdfPage = CGPDFDocumentGetPage(pdfDoc, 1);
Then I create a box with the same dimensions as the loaded PDF:
CGRect box = CGPDFPageGetBoxRect(pdfPage, kCGPDFArtBox);
Then I save my graphics state, so that I don't screw anything up:
CGContextSaveGState(context);
And then I perform a scale+translate of the CTM, theoretically flipping the whole context:
CGContextScaleCTM(context, 1.0, -1.0);
CGContextTranslateCTM(context, 0.0, rect.size.height);
I then scale the PDF so that it fits into the view properly:
CGContextScaleCTM(context, rect.size.width/box.size.width, rect.size.height/box.size.height);
And finally, I draw the PDF and restore the graphics state:
CGContextDrawPDFPage(context, pdfPage);
CGContextRestoreGState(context);
The issue is that there is nothing visible drawn. All this code should theoretically draw the PDF glyph into the view, right?
If I remove the scale+translate used to flip the context, it draws perfectly: it just draws upside-down.
Any ideas?
