Draw Image to PDF

Question

I'd like to draw an full page image to a PDF but I've always had a hard time wrapping my head around CGContextRefs so I don't know what to make of the error.

Note, this is NOT iOS. I'm making a desktop application.

So far, I have this:

-(void) addImage:(NSURL*) url toPage:(size_t) page toPDF:(CGPDFDocumentRef) pdf
{
    NSImage *image = [[NSImage alloc] initWithContentsOfURL:url];
    image = [image imageScaledToFitSize:pageSize.size];  //From Matt Gemmell's Crop extensions category

    [image lockFocus];

    CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort];
    [image drawInRect:pageSize];
    [image unlockFocus];


    CGPDFPageRef pageRef = CGPDFDocumentGetPage(pdf, page);

    CGPDFContextBeginPage(context, pageInformation);
    CGContextDrawPDFPage(context, pageRef);
    CGPDFContextEndPage(context);
}

However, I'm greeted with the error:

CGPDFContextEndPage: invalid context 0x61000017b540. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

What is wrong with my contexts please?

Answer 1

You need to create and use a CGPDFContext. Different contexts are specific to different rendering processes / destinations so you need to choose the correct one. So look at using CGPDFContextCreateWithURL to create a PDF context to write the data to a file.