Single-Page vs. Multi-Page TIFF Files

A Single-Page TIFF file is a file which contains a single image/page that is stored in a TIFF image format.

Multiple-Page TIFF File:

A Multiple-Page TIFF file is a file which contains one or more images/pages that are stored in a TIFF image format.

When you perform a download on the internet, you are downloading a single file at a time.

When a document is made up of multiple "single-page" TIFF files, you have to download a file (a single page), view that page and then go back and download the next file/page to view it.

When a document is made up of a single "multiple-page" TIFF file, you download that single file. When you view that file in a multiple-page TIFF viewer, the viewer gives you the option to page through the various images (pages) in that file.

The size of a multiple-page TIFF file containing 10 pages is almost identical to sum of the sizes of those same 10 single-page TIFF files. Therefore, you usually do not save much (if any) time in the actual download of a single multiple-page TIFF file over that of the actual download of those same files in single-page TIFF form. The good news is that it does not take any longer, either.

The biggest advantage to downloading a document in the "multiple-page" TIFF file version over downloading a document in the single-page TIFF file version is that you only have to go start that download once for the multiple-page TIFF file. You can then go work on some other task (like getting a fresh cup of coffee) and come back later to page through all the pages.

The disadvantage to downloading a document in the multiple "single-page" TIFF file version is that you have to stick with it until you are done. You download one page, read it, then start the download of the next page. By the time you get to the next page, you are in danger of forgetting where you just left off on the last page.

More than you really want to know about Multiple-Page TIFF files:

If you really, really want to get into the nitty gritty of what makes up a TIFF file, you could try to download the file ("White Paper") "tiff6.pdf" from Adobe. It is the document I used to write the utility used on this system to build the multiple-page TIFF files out of the single-page TIFF files.

I found it at...

ftp.adobe.com/pub/adobe/devrelations/devtechnotes/pdffiles/tiff6.pdf

...there is no guarantee it will still be there.

In case you are not that insatiably curious, I will just give you a few points that may be relative here, though more than you need to know to just use the system.

In a single-page TIFF file, the first 8 bytes are the image header.

The first 2 bytes define whether the TIFF image is a "little endian" or a "big endian". Basically that means whether a group of bytes are read from left to right or right to left.

The next 2 bytes are (and I will quote the white paper because I love the inside humor), "An arbitrary but carefully chosen number (42) that further identifies the file as a TIFF file."

The next 4 bytes are the offset to the start of the section of "tags" that tell the viewer how to display the image.

After those first 8 bytes, there is a series of bytes that contain tags, types, counts, and values. This "tag section" is officially called the "Image File Directory".

After that tag section, there is an 8 byte section that is the offset (in number of bytes) to the start of the tag section for the next page. For a single-page TIFF file, this value would be zero. If the value is zero, the viewer knows not to try to find another page.

In a multiple-page TIFF file, the first page is identical to the single-page Tiff file except for that offset to the start of the tag section for the next page because in this case there IS a next page.

Unfortunately, the tags in that "tag section" can also contain multiple offsets and those offsets are relative to the very beginning of the file and not to the beginning of the page. So, when you are building a multiple-page TIFF file out of several single-page TIFF files, you must tweak all of those offsets for every page after the first page.

You also have to calculate where the tag section of the next page will begin (relative to the very top of the file) even before you have finished writing the current page because you have to write that offset long before you finish writing the current page.

For every page (after the first page) you do NOT write the first 8 bytes from each of those single-page TIFF files. You start those pages with the beginning of the "tag section" for those pages. Those 8 bytes only occur at the very beginning of the file and NOT at the beginning of every page.

When you finally write the last page, you must set the offset to the start of the tag section for the next page to zero because there is not going to be a next page.

The moral behind all of this is that if you create the multiple-page TIFF file without adding any new tags of your own, the multiple-page TIFF file will be slightly smaller than the sum of the sizes of all the single-page TIFF files because all pages after the first will be 8 bytes smaller than their single-page TIFF file counterparts.

However, on this system, we do add one tag and a "pad" which are a total of approximately 384 bytes in length. That means that the multiple-page TIFF file would have to have more than 49 pages for the multiple-page TIFF file to be smaller than the sum of the sizes of the single-page TIFF files.

But, even if the multiple-page TIFF file were 1,000 bytes larger than the sum of the sizes of the single-page TIFF files, it would be faster (and much less labor) to download the multiple-page TIFF file because you would not have to go back and restart the download for every single page.

As I said above, "More than you really want to know about Multiple-Page TIFF files...."