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Editorial Team
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Asked: 2026-05-14T04:53:19+00:00

I’m trying to take an image that I have in a image object and

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I’m trying to take an image that I have in a image object and render into a Core Graphics PDF context– happens to be on an iPhone but this question surely applies equally to desktop Quartz. This UIImage is a simple color-on-white image at about 600×800 resolution. If I (say) turn it into a PNG file, that file looks exactly as expected– so the data is OK.

Here’s what I’m doing to generate the PDF:

NSMutableData * outputData = [[NSMutableData alloc] init];
CGDataConsumerRef dataConsumer = CGDataConsumerCreateWithCFData((CFMutableDataRef)outputData);

CFMutableDictionaryRef attrDictionary = NULL;    
attrDictionary = CFDictionaryCreateMutable(NULL, 0,
                                         &kCFTypeDictionaryKeyCallBacks,
                                         &kCFTypeDictionaryValueCallBacks);
CFDictionarySetValue(attrDictionary, kCGPDFContextTitle, @"My Awesome Document");
CGContextRef pdfContext = CGPDFContextCreate(dataConsumer, NULL, attrDictionary); 
CFRelease(dataConsumer);
CFRelease(attrDictionary);
CGImageRef pageImage = [myUIImage CGImage];
CGPDFContextBeginPage(pdfContext, NULL);
CGContextDrawImage(pdfContext, CGRectMake(0, 0, [myUIImage size].width, [myUIImage size].height), pageImage);
CGPDFContextEndPage(pdfContext);
CGPDFContextClose(pdfContext);
CGContextRelease(pdfContext);

The resulting PDF, which ends up in outputData, seems like a valid PDF file (opens correctly, document title is present in metadata), but it consists of precisely one blank page.

What am I doing wrong?

Thanks.

UPDATE: Ha! This was my fault. My test code for just generating the PNG file went through a different path to get the data. The PDF path indeed was receiving an empty image.

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1 Answer

  1. Editorial Team

    I tested your code and it seems to work.
    Are you sure your UIImage is valid and not nil when drawing it into the context?
    My test method loads a .png from the main bundle and writes the final pdf to a file in the applications document folder:

    - (IBAction)outputPDF:(id)sender
{
    NSMutableData* outputData = [[NSMutableData alloc] init];
    CGDataConsumerRef dataConsumer = CGDataConsumerCreateWithCFData((CFMutableDataRef)outputData);
    CFMutableDictionaryRef attrDictionary = NULL;    
    attrDictionary = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    CFDictionarySetValue(attrDictionary, kCGPDFContextTitle, @"My Awesome Document");
    CGContextRef pdfContext = CGPDFContextCreate(dataConsumer, NULL, attrDictionary); 
    CFRelease(dataConsumer);
    CFRelease(attrDictionary);
    UIImage* myUIImage = [UIImage imageNamed:@"tmp.png"];
    CGImageRef pageImage = [myUIImage CGImage];
    CGPDFContextBeginPage(pdfContext, NULL);
    CGContextDrawImage(pdfContext, CGRectMake(0, 0, [myUIImage size].width, [myUIImage size].height), pageImage);
    CGPDFContextEndPage(pdfContext);
    CGPDFContextClose(pdfContext);
    CGContextRelease(pdfContext);   
    NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString* documentsDirectory = [paths objectAtIndex:0];
    NSString* appFile = [documentsDirectory stringByAppendingPathComponent:@"tmp.pdf"];
    [outputData writeToFile:appFile atomically:YES];
}
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