Convert a PDF to one page PDF reason for this is PDF pages doesnot have same page height [closed]

问题

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Closed 6 years ago.

I have a PDF and I want to shrink it down to one page.

This does not work:

//pages
size_t pages = CGPDFDocumentGetNumberOfPages(document);
pageRect.size.height = pageRect.size.height*pages;
CGDataConsumerRef dataConsumer = CGDataConsumerCreateWithCFData(mutableData);
CGContextRef pdfContext = CGPDFContextCreate(dataConsumer, &pageRect, NULL);

CGPDFContextBeginPage(pdfContext, NULL);
for (int i =1; i<=pages; i++)
{
   CGPDFPageRef pageRef = CGPDFDocumentGetPage(document, i);
   CGContextDrawPDFPage(pdfContext, pageRef);
}
CGPDFContextEndPage(pdfContext);

回答1:

Your code prints all the pages at the same location, one on top of another. If by any chance the pages have an explicit white background then you will see only the last page.
The solution is to translate the coordinate system after the page is drawn with the height of the page that has been drawn.
UPDATE: This is the complete code. It assumes that all pages in the source file have the same size and rotation:

NSURL *pdfURL = [[NSBundle mainBundle] URLForResource:@"source.pdf" withExtension:nil];
pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);

int pageCount = CGPDFDocumentGetNumberOfPages(pdf);
CGPDFPageRef pageRef = CGPDFDocumentGetPage(pdf, 1);
CGRect pageRect = CGPDFPageGetBoxRect(pageRef, kCGPDFMediaBox);
float pageHeight = pageRect.size.height;
pageRect.size.height = pageRect.size.height * pageCount;

NSMutableData* pdfData = [[NSMutableData alloc] init];
CGDataConsumerRef pdfConsumer = CGDataConsumerCreateWithCFData((CFMutableDataRef)pdfData);
CGContextRef pdfContext = CGPDFContextCreate(pdfConsumer, &pageRect, NULL);

CGPDFContextBeginPage(pdfContext, NULL);
CGContextTranslateCTM(pdfContext, 0, pageRect.size.height);
for (int i = 1; i <= pageCount; i++) {
    pageRef = CGPDFDocumentGetPage(pdf, i);
    CGContextTranslateCTM(pdfContext, 0, -pageHeight);
    CGContextDrawPDFPage(pdfContext, pageRef);
}
CGPDFContextEndPage(pdfContext);
CGPDFContextClose(pdfContext);

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *pdfFile = [documentsDirectory stringByAppendingPathComponent:@"destination.pdf"];

[pdfData writeToFile: pdfFile atomically: NO];
[pdfData release];

来源：https://stackoverflow.com/questions/17025701/convert-a-pdf-to-one-page-pdf-reason-for-this-is-pdf-pages-doesnot-have-same-pag