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Topic: Re: Replacing The Image
Conf: (P-PDF) Developers, Msg: 58390
From: LeonardR
Date: 5/29/2002 05:32 PM

At 12:50 AM +1100 11/2/01, p-pdf-developer Listmanager wrote:
>I am using libjpeg and Zlib to replace the image if the PDF is using FLATE
>filter. What i am doing is.

If the image is already using FLATE, then it's NOT JPEG
compressed. A filter of DCTFilter means JPEG.

>1) Decompress the jpeg image with libjpeg.
>2) Recompress the decompressed data using Zlib and passing between stream
>and endstream.

That certainly works, but seems pretty silly since the images
will be LARGER when flatted than when DCT'd, since JPEG is a lossy
algorithm while flate is lossless.

>Now i am trying to do the same thing for the TIFF image.
>1) Decompress the image using libtiff.
>2) Recompress the decompressed data using Zlib.
>is that correct way ? Please advice me on this issue.
Data compressed using CCITT filters are NOT native TIFF - you
have to put some extra stuff around the data in the PDF to actually
have it be processed by libtiff.

But the better question is WHY are you doing this??

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