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From Yegor Kozlov <ye...@dinom.ru>
Subject Re[2]: Image extraction
Date Mon, 16 Jan 2006 13:41:33 GMT
Hi Nick,

"Pictures" OLE stream is a tightly packed sequence of HEADER + picture
data. Header is 25 bytes. JPEG and PNG are stored as-is. BMP and WMF
are compressed. New pictures are added to the end with no change to
the start.

For each picture there is a EscherBStoreContainer defined on the
document level. It stores checksum and offset to the picture in the
"Pictures" stream.

>From slide's point of view Picture is a shape. That is for each picture in a
slide there is a EscherSp container with information about position, borders,
etc. EscherSp refers to EscherBStoreContainer which knows about image
position in the "Pictures" stream.

Regards, Yegor

NB> On Mon, 16 Jan 2006, Yegor Kozlov wrote:
>> PowerPoint stores images in a separate OLE stream named "Pictures".

NB> Looking at the supplied file, I can confirm that

>> Extracting image data from it is not difficult, I will commit the patch 
>> in a couple of days.

NB> That would be great, thanks. For now, probably just a method on 
NB> HSLFSlideShow (like the DocumentSummaryInformation/SummaryInformation 
NB> ones) is probably all we need. That said, if you fancied adding the 
NB> records to make use of them, that'd be even better :)

NB> OOI, how does PPT know how many images are in the pictures block? It looks 
NB> to me (on adding a second PNG) that it just appends it in the block, with 
NB> no change to the start. Is it just an atom like structure, or something 
NB> fancier?

NB> Nick

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