iOS embedd page thumbnails in PDF - ios

Question

I need to embed thumbnails in large hq PDF files, which I create using UIGraphicsBeginPDFContextToFile and UIGraphicsBeginPDFPage and drawing text and images on them.
Does anyone know, how to embed page thumbs?
Ciao, Arno

Answer 1

If you want to create a thumbnail from a PDF, then you could use the code below. This code writes it to disk. It's easy to change it so that the method returns the image.
- (void)createPDFThumbnailForFile:(NSString *)theFilename {
if (!theFilename) {return;}
#try {
NSString *path = [FileInfo fullPathForFile:theFilename];
NSURL *pdfFileUrl = [NSURL fileURLWithPath:path];
CFURLRef pdfFileRef = (__bridge CFURLRef) pdfFileUrl;
CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL(pdfFileRef);
CGPDFPageRef page;
CGRect aRect = CGRectMake(0, 0, 70, 100); // thumbnail size
UIGraphicsBeginImageContext(aRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
UIImage *thumbnailImage;
// NSUInteger totalNum = CGPDFDocumentGetNumberOfPages(pdf);
//we only want the first page
for (int i = 0; i < 1; i++) {
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0.0, aRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetGrayFillColor(context, 1.0, 1.0);
CGContextFillRect(context, aRect);
// Grab the first PDF page
page = CGPDFDocumentGetPage(pdf, 1);
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFMediaBox, aRect, 0, true);
// And apply the transform.
CGContextConcatCTM(context, pdfTransform);
CGContextDrawPDFPage(context, page);
// Create the new UIImage from the context
thumbnailImage = UIGraphicsGetImageFromCurrentImageContext();
CGContextRestoreGState(context);
}
CGPDFDocumentRelease(pdf);
NSString *pngPath = [path stringByReplacingOccurrencesOfString:#".pdf" withString:#".png"];
// [#"test" writeToFile:pngPath atomically:YES encoding:NSUTF8StringEncoding error:nil];
[UIImagePNGRepresentation(thumbnailImage) writeToFile:pngPath atomically:YES];
}
#catch (NSException *exception) {
DebugLog(#"Could not write thumbnail to : %# /n --> %#", theFileToSave, exception.description);
}
}