Handmade Gif (2006)
Handmade Gif is a Gif file I wrote by hand in binary. This of course is pointless, but I chose to do this as an exercise in order to familiarize myself with the basics of compression for no reason other then I wondered how it worked. Since Gif was the oldest common compression format, I picked it first. And because I was writing it by hand I picked a really small and easy one to do, which was a 2 pixel wide by 2 pixel high square. Black, White, on top of White, Black. In fact the period at the end of this sentence is actually the gif (yes, cause it’s that small)
Gif Code Explanation
header: 474946383961
image map size: 0200 0200
global color flag, not sorted, 1 bit per color, size of color table 2: 80
no background (unused): 00
no pixel aspect ratio: 00
black: 000000
white: FFFFFF
image separator: 2C
image distance from l / r in image map: 0000 0000
image size: 0200 0200
non interlaced, and no local colors (not sorted and no size): 00
size of LZW code chunks (=3): 02
length of LZW code section: 03
LWZ code: 448202
next LZW code size: 00
end of file: 3B
It is a 2 by 2 black and white checker GIF…
BW WB
LZW Compression Notes
