Rendering UIImage/CGImage into CGPDFContext results in... blankness!
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 600x800 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,
开发者_开发百科 &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.
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];
}
This issue seems to have been addressed on the iphone dev sdk forums: PDF creation tutorial
All credit goes to danielb21: here is a reprint of their CreatePDFFile method:
// Our method to create a PDF file natively on the iPhone
// This method takes two parameters, a CGRect for size and
// a const char, which will be the name of our pdf file
void CreatePDFFile (CGRect pageRect, const char *filename) {
// This code block sets up our PDF Context so that we can draw to it
CGContextRef pdfContext;
CFStringRef path;
CFURLRef url;
CFMutableDictionaryRef myDictionary = NULL;
// Create a CFString from the filename we provide to this method when we call it
path = CFStringCreateWithCString (NULL, filename,
kCFStringEncodingUTF8);
// Create a CFURL using the CFString we just defined
url = CFURLCreateWithFileSystemPath (NULL, path,
kCFURLPOSIXPathStyle, 0);
CFRelease (path);
// This dictionary contains extra options mostly for 'signing' the PDF
myDictionary = CFDictionaryCreateMutable(NULL, 0,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
CFDictionarySetValue(myDictionary, kCGPDFContextTitle, CFSTR("My PDF File"));
CFDictionarySetValue(myDictionary, kCGPDFContextCreator, CFSTR("My Name"));
// Create our PDF Context with the CFURL, the CGRect we provide, and the above defined dictionary
pdfContext = CGPDFContextCreateWithURL (url, &pageRect, myDictionary);
// Cleanup our mess
CFRelease(myDictionary);
CFRelease(url);
// Done creating our PDF Context, now it's time to draw to it
// Starts our first page
CGContextBeginPage (pdfContext, &pageRect);
// Draws a black rectangle around the page inset by 50 on all sides
CGContextStrokeRect(pdfContext, CGRectMake(50, 50, pageRect.size.width - 100, pageRect.size.height - 100));
// This code block will create an image that we then draw to the page
const char *picture = "Picture";
CGImageRef image;
CGDataProviderRef provider;
CFStringRef picturePath;
CFURLRef pictureURL;
picturePath = CFStringCreateWithCString (NULL, picture,
kCFStringEncodingUTF8);
pictureURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), picturePath, CFSTR("png"), NULL);
CFRelease(picturePath);
provider = CGDataProviderCreateWithURL (pictureURL);
CFRelease (pictureURL);
image = CGImageCreateWithPNGDataProvider (provider, NULL, true, kCGRenderingIntentDefault);
CGDataProviderRelease (provider);
CGContextDrawImage (pdfContext, CGRectMake(200, 200, 207, 385),image);
CGImageRelease (image);
// End image code
// Adding some text on top of the image we just added
CGContextSelectFont (pdfContext, "Helvetica", 16, kCGEncodingMacRoman);
CGContextSetTextDrawingMode (pdfContext, kCGTextFill);
CGContextSetRGBFillColor (pdfContext, 0, 0, 0, 1);
const char *text = "Hello World!";
CGContextShowTextAtPoint (pdfContext, 260, 390, text, strlen(text));
// End text
// We are done drawing to this page, let's end it
// We could add as many pages as we wanted using CGContextBeginPage/CGContextEndPage
CGContextEndPage (pdfContext);
// We are done with our context now, so we release it
CGContextRelease (pdfContext);
}
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