[stella] OT: Image formats

Subject: [stella] OT: Image formats
From: Glenn Saunders <cybpunks2@xxxxxxxxxxxxx>
Date: Sun, 16 Sep 2001 13:25:05 -0700
At 03:36 PM 9/16/2001 -0400, you wrote:
Is the Unisys GIF patent still active?

It's not an issue for those creating GIFs, just for programs that manipulate them, and even then, it's arguable how enforcable it is.

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

JPEG is by definition either 8-bit greyscale or 24-bit. GIF is paletted which is ideal for an image like this. If you create a GIF with a 128 color palette (7-bit, not all programs support this) then it is going to almost certainly be smaller than a JPEG at the same resolution. It doesn't have to store as much information.

If you are talking about storing a 1 pixel image rather than an entire matrix of the palette, then the GIF can be even smaller by using only a 1-bit palette.

PNG is the best lossless compression of all and IE supports them. I don't know about other browser support. PNG has countless advantages over GIF, the biggest for me being its support for 24-bit and 32-bit (24bit plus alpha channel) formats. IE doesn't render the alpha channel, though.

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