[Nex]

Since I have been checking to find the best file format to store quick sketches I thought I would let you drink from my thurst quenching well of neverending wisdom and share:

The base picture was a (f**ed up) sketch I made from the Spooge-Demon-old-man-picture-thread.



gif 89a
(no error diffusion): 33,9 KB
gif 89a, interlaced
(no error diffusion ): 34,2 KB
jpg baseline compression
( 90% Quality): 81,9 KB
jpg baseline optimized compression
( 90% Quality): 72,6 KB
jpg progressive, 3 Level Compression
( 90% Quality): 71,1 KB
png: 67,9 KB
pcx: 156 KB
tif, LZW Compression: 97,2 KB
targa, 24 bit: 351 KB
targa, 16 bit: 234 KB
pixar: 353 KB
psd: 161 KB

So the winner is:...

GIF 89a hurray!!!

The sucker for storing sketches is: pixar *.pxr Format.

Thats it.

Flowers, donations and blood sacrifices will be appreciated

[Cos]

so why have I been using jpegs all this time? .....hmmmmmmm DOH! Thanx nex!

[synj]

yes, nex. i agree that GIFs are definately good if there is not alot of colors being used in the palette. thats how i am able to create such quick loading images at www.synj.net/seconds.htm

there is a bit more to it when it involves color, but i wont go into that part since we're talking about sketches

regards,
-synj www.synj.net

[spooge demon]

Thanks nex for the grunt work. I agree with Synj. Try the same test with the photo. I did and the jpeg won.? Maybe I did something wrong...

i think jpgs were designed for photos and gifs are better for flat colors.

[Cos]

I think jpeg's get like 5000 or something colours in them, and gifs get 256 max, so jpeg would definetely be better for photos. So why have you been using jpegs for your sketches cos? erm.......

[Nex]

Yup, for full color jpg is smaller and a very good solution, for sketches (with only about 5 or 6 color [greytones maybe]) gifs are smaller. Depends on the pic very much.

[kos.mandis]

I've found out that acdsee32 does a better job(!) (sizewise) when converting and image to a jpeg rather than save it as jpeg from photoshop...

(tested an image saved as jpeg from photoshop at 6/12 quality got 113 kbs whereas converting the psd to a jpeg with acdsee got it at 83kbs-at 50% quality)

[Frost]

Gifs encode using a predefined color table of 8bits, meaning 256 colors max, while JPG works in 16777216 colors, or true color, where you have the equivalent of 3 8bit images, storing the RGB info of each pixel at 256 levels each (256^3). (1 pixel = 3 bytes in 24-bit, 1 pixel = 4 bytes in 32-bit)

Indexed color is different than true color in that each pixel is an index number corresponding to a preset RGB in the palette, instead of an independant color definition, so all pixels share the same predefined 256 (or less) colors.

Of course, GIF has been around since 1987 and uses some real nice LZ compression which is also conincidentally used in the ZIP file format to some extent (zip has improved the algos a lot over the years, while GIF stayed behind for compatibilities' sake).

How LZ (GIF) works is that it basically looks back into the file to see if it already encountered the upcoming series of pixels, and if a match already existed, it writes an index to the offset in the image where that string already existed, saving much space, especially in images with little color or huge blocks of uniform color.

JPG uses a block compression algo that I don't know about... but I know it compresses in CHUNKS, or blocks -- you can easily see them if you boost saturation of a JPG to 100%... you'll see block patterns appearing.

PNG works both in indexed mode and true color, so it natively supports both 256 color indexed images and true color (24-bit) images (+ alpha transparency for 32-bit images).

frost.

[This message has been edited by Frost (edited May 17, 2000).]

[Cos]

Well I was quite close saying 5000... DOH!!

[Francis]

Frost is deep in propellerhead country...

------------------
TeamGT Studios

[Frost]

Francis: I don't know what the expression means, but, I'll take that as a compliment. (!)

Being in the gaming and programming environment for too long does that to you. =)

[This message has been edited by Frost (edited May 17, 2000).]