How to generate thumbnails from a PDF document with iPhone SDK?

Question

I have read the Apple PDF documentation with Quartz.

But I do not know how to generate the thumbnails from a PDF document...

Any idea/sample code ?

Answer 1

In the meantime I have created a library which does support PDF, Images and Videos for creating thumbnails. Maybe someone else can use it:

https://github.com/prine/ROThumbnailGenerator

Solution in Swift. Just pass the NSURL to the PDF and the page number you want to retrieve as UIImage:

func getThumbnail(url:NSURL, pageNumber:Int) -> UIImage {

    var pdf:CGPDFDocumentRef = CGPDFDocumentCreateWithURL(url as CFURLRef);

    var firstPage = CGPDFDocumentGetPage(pdf, pageNumber)

    // Change the width of the thumbnail here
    var width:CGFloat = 240.0;

    var pageRect:CGRect = CGPDFPageGetBoxRect(firstPage, kCGPDFMediaBox);
    var pdfScale:CGFloat = width/pageRect.size.width;
    pageRect.size = CGSizeMake(pageRect.size.width*pdfScale, pageRect.size.height*pdfScale);
    pageRect.origin = CGPointZero;

    UIGraphicsBeginImageContext(pageRect.size);

    var context:CGContextRef = UIGraphicsGetCurrentContext();

    // White BG
    CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
    CGContextFillRect(context,pageRect);

    CGContextSaveGState(context);

    // ***********
    // Next 3 lines makes the rotations so that the page look in the right direction
    // ***********
    CGContextTranslateCTM(context, 0.0, pageRect.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextConcatCTM(context, CGPDFPageGetDrawingTransform(firstPage, kCGPDFMediaBox, pageRect, 0, true));

    CGContextDrawPDFPage(context, firstPage);
    CGContextRestoreGState(context);

    var thm:UIImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
    return thm;
}