Gif or tiff files recommended for a PDF for publication?

Question

Hello,
I recently lost all the source files (InDesign of course) for a PDF that I created, but I still have the PDF itself. I bought some software (recosoft) that allows
me to open the PDF in InDesign, but I am given the choice of opening the images in the PDF as either gif or tiff files. Since the PDF needs to be edited more and will eventually be sent out to for publication, can anyone tell me which would be better, to have the images converted into gif or tiff? There are hundreds of images and they are integral to the (black and white) book.
Thanks in advance!
James

Answer 1

Properly speaking, the question is underspecified.
GIF is a file format that supports 8-bit color and no dpi specification, and is generally assumed to be 72dpi but the user can always indicate the image should be scaled appropriately, and supports limited transparency. It uses lossless compression, which means it is a very good file format indeed when compared to JPEG, if you are dealing with line art, text, or hard edges.
TIFF is a container file format. It has hundreds of different options (which is to say, millions of combinations of options), can be compressed lossily or losslessly (but is usually lossless), and supports a wide array of bit depths and color spaces, as well as metainformation including the resolution/dpi. It's easy to produce TIFF files with options that are wrong for any particular purpose.
Most of the time, if you are forced to choose between GIF and TIFF, you should choose TIFF. But if your images meet GIF's somewhat narrow constraints, you are probably better off choosing GIF. Certainly with GIF you know what you're getting. A lot depends on what the software is actually doing, which can be unknowable.
(A more common and frequently confused dilemma is JPEG versus GIF, and many people mistakenly choose JPEG when the image is not suitable for JPEG compression, and this can be a horrible horrible mistake that continues to make me feel sick every time I see the results, which is all-too-frequently.)
In this case, though, one has to wonder what the software developers were thinking. I'm not familiar with recosoft, but PDFs store images in only a small number of ways. They can be compressed lossily with JPEG compression, and they can be stored losslessly with a few other choices (the specifics of which don't matter too much because they are lossless!) like Flate (aka Zip), CCITT/Fax, LZW, and no compression at all.
When you're extracting an image from a PDF, what should be important is that you don't transcode the image through a lossy compression step. That is, if it was saved in the PDF with JPEG compression, you want to extract it with JPEG compression. If it was saved in the PDF without JPEG compression, you want to extract it without JPEG compression. Any time you change lossy compresson formats, you introduce artifacts, which are usually undesirable. There's no way to tell from looking at the PDF what non-lossy format the image originally was (e.g. to distinguish a PNG from GIF), but JPEGs are clearly identifable.
I usually use the free command-line tool pdfimages to extract images from PDFs, using the -j option to preserve JPEG compression where appropriate. pdfimages is part of xpdf. You can also do it with Acrobat Professional, though offhand I forget if it has a setting that is smart enough to extract JPEGs automatically where appropriate.