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Uncompressed GIF Image Algorithm Disclosure Number: IPCOM000131070D
Original Publication Date: 2005-Nov-07
Included in the Prior Art Database: 2005-Nov-07
Document File: 1 page(s) / 25K

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Uncompressed GIF Image Algorithm

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Uncompressed GIF Image Algorithm Background

We needed a way to convert icons on a palm device into GIF files. GIF files are generally compressed by means of LZW compression which is licensed technology that must be cleared for use. We also found a solution on-line that used Run Length Encoding (RLE) to generate a readable GIF file, but that also required clearance to use it. Looking at the GIF file format, it seemed fairly straightforward to generate an algorithm to take the icon (which at this point in the code was an indexed bitmap) and create an uncompressed GIF file from it.

Invention Summary

Take an indexed bitmap (equal to or less than 256 colors) and convert it into an GIF file without compressing the image. Each pixel of the bitmap is merely an index into a color table, so simply read the pixel's index from the bitmap and write it to the GIF file.

Since we were dealing with small images, the data size increase was not an issue (the header of the GIF file is larger than our data). Also, with this solution we did not have to go through the trouble of getting permission to use an established compression/decompression solution, such as LZW compression or above mentioned RLE solution.

As stated, the main advantage, and the original goal, was to get around legal issues. Beyond that issue, the GIF file that we generate and a regular LZW GIF file both behave the same. Our files are readable as GIF files and are displayed correctly when viewed.

Implementation Deta...