Re: Decoding images in PDF files
Re: Decoding images in PDF files
- Subject: Re: Decoding images in PDF files
- From: Antonio Nunes <email@hidden>
- Date: Mon, 26 Aug 2013 19:07:13 +0100
On 26 Aug, 2013, at 18:49 , Graham Cox <email@hidden> wrote:
> I'm working on a parser that needs to be able to extract graphics from PDF files. So far, I'm making good headway with the CGPDFxxx functions.
>
> I have a question about extracting embedded bitmap images. When I encounter an XObject stream with subType /Image, I get a bunch of parameters that looks pretty close to the parameters to CGImageCreate. However, the 'Filter' parameter indicates /FlateDecode so I'm assuming that I can't just wrap the stream in a CFDataRef and then in a CFDataProvider - I'll need to actually decompress this data first using (according to PDF spec) zlib/deflate.
>
> Am I right? Anyone got any sample code or hints regarding how to go about this?
No, you shouldn't need to decompress it. Something like the following should get you the data:
[…snip…]
imageDataPtr = CGPDFStreamCopyData(dataStream, &format);
dataProvider = CGDataProviderCreateWithCFData(imageDataPtr);
CFRelease(imageDataPtr);
[…snip…]
Message me privately if you want some more help with this Graham.
-António
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