On Sun, 16 Sep 2001, Glenn Saunders wrote:
> GIF would be better than JPEG. JPEG is really for photographs.
>
Is the Unisys GIF patent still active?
Anyway, the conventional purpose of a compression algorithm sort of goes
out the window when we are talking about a 1 x 1 pixel image. JPEG
compression divides the image into 8 x 8 pixel tiles, and uses pattern
primitives that get combined in certain ways to approximate the original
image, so it *should* be lossless in the specific case of a 1 x 1 pixel
image. In an attempt to verify that, I fired up Photoshop and created
three 1 x 1 pixel files from the $56 swatch from my palette file (the
losslessly compressed Photoshop formatted version of it was used as the
original) One was GIF, and it was the smallest, 3356 bytes. I created
two JPEG files, one at the zero quality setting, and one at the ten
setting. The former came out at 3827 bytes, and the latter 3962 bytes.
All three files maintained the exact color value of its one pixel, which
is RGB: 192, 74, 220, which is the value that Mac Stella assigns to NTSC
COLU value $56. Since Photoshop is obviously not optimized to create
1 x 1 pixel files, it may be possible to create a much smaller valid GIF
or JPEG representations of single pixel, arbitrary color.
Of course, it would still be 128 HTTP connections.
Additional trivia: It is the 8 x 8 pixel tile arangement of JPEG that
makes it impossible to arbitrarally crop a JPEG file without then having
to recompress it and lose more quality. Always store your photo originals
in a lossless format and only convert to JPEG for specific final versions.
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