Contex Drawing + Pagination

Question

I am trying to draw contents of scrollview into a PDF context & I am facing problem with pagination.

Following Code I have used:

- (void)renderTheView:(UIView *)view inPDFContext:(CGContextRef)pdfContext {     // Creating frame.     CGFloat heightOfPdf = [[[self attributes] objectForKey:SRCPdfHeight] floatValue];     CGFloat widthOfPdf  = [[[self attributes] objectForKey:SRCPdfWidth] floatValue];     CGRect pdfFrame = CGRectMake(0, 0, widthOfPdf, heightOfPdf);        CGRect viewFrame = [view frame];      if ([view isKindOfClass:[UIScrollView class]])     {         viewFrame.size.height = ((UIScrollView *)view).contentSize.height;         [view setFrame:viewFrame];     }     // Calculates number of pages.     NSUInteger totalNumberOfPages = ceil(viewFrame.size.height/heightOfPdf);      // Start rendering.     for (NSUInteger pageNumber = 0; pageNumber<totalNumberOfPages; pageNumber++)     {        // Starts our first page.        CGContextBeginPage (pdfContext, &pdfFrame);          // Turn PDF upsidedown        CGAffineTransform transform = CGAffineTransformIdentity;        transform = CGAffineTransformMakeTranslation(0,view.bounds.size.height);        transform = CGAffineTransformScale(transform, 1.0, -1.0);        CGContextConcatCTM(pdfContext, transform);         // Calculate amount of y to be displace.        CGFloat ty = (heightOfPdf*(pageNumber));         CGContextTranslateCTM(pdfContext,0,-ty);        [view.layer renderInContext:pdfContext];         // We are done drawing to this page, let's end it.        CGContextEndPage (pdfContext);    }     } 

It creates required number of pages but places the content wrongly. Following figure explains it.

Is there anything wrong in my code?

Answer 1

I don't think you need the code which flips the PDF upside down. I've done this before (manual pagination, but without a scroll view) and never had to flip the context vertically. My main concern is that you are doing it on every iteration - if you have a valid reason for flipping it, you probably don't need it in the loop, but just once before the loop begins. Also the code CGContextTranslateCTM(pdfContext,0,-ty); might need to be replaced with CGContextTranslateCTM(pdfContext,0,heightOfPdf);

If that doesn't work, try UIGraphicsBeginPDFPage(); instead of CGContextBeginPage(), that's the only major difference between your code and mine.

Answer 2

This github project can definitely help you.

- (void) renderPageAtIndex:(NSUInteger)index inContext:(CGContextRef)ctx { CGPDFPageRef page = CGPDFDocumentGetPage(pdf, index + 1); CGAffineTransform transform = aspectFit(CGPDFPageGetBoxRect(page, kCGPDFMediaBox),                                         CGContextGetClipBoundingBox(ctx)); CGContextConcatCTM(ctx, transform); CGContextDrawPDFPage(ctx, page); 

}