Scanning Documents

markcg2000 · Jan 17, 2001

Harv,
Maybe the pallette or the number of colors? If your conversion is mixing one JPG color into a couple of close-but-no-cigar GIF colors?

mark

Muhammad · Jan 17, 2001

Hmm, Harv, figure this one out! /w3tcompact/icons/wink.gif

37k GIF attached...

Harv · Jan 17, 2001

Mark -

Not quite sure what you're saying.

Bird's image happens to consist of 130 shades of gray, so the adaptive gif color table would be an exact match.

The JPEG compression algorithms (way gnarly) are geared to "continuous tone" images such as found in real-life photographs. Since Bird's image consists primarily of sharp transitions, it should lend itself more to the GIF format, which is more run-length encoded.

My best guess is that because it was scanned as a grayscale image, the apparent sharp edges actually consist of short gradients (which gives much smoother-looking lines, by the way). That's why what appears to be a black and white picture actually contains 130 shades of gray. Apparently if there is enough of these kinds of gradients, JPEG will do a better job.

Either that, or it's magic. /w3tcompact/icons/laugh.gif

Harv · Jan 17, 2001

figure this one out!

You're playing with my head, Muhammad!!! /w3tcompact/icons/shocked.gif

That's the result I was expecting, but when I used Photoshop to create the gif, it was nowhere near that small.

Fess up, Dude! What did I miss? /w3tcompact/icons/crazy.gif

Bird · Jan 17, 2001

Heck, I don't even know what you guys are talking about, but I'm using the software that came with this Hewlett-Packard Office Jet 520 printer, and if it helps any, when you scan anything, it offers the options of Text, Photo, Graphic, or Other Custom Settings. I selected Photo simply because it indicated that would be the smallest file, and it said it scanned at 150 x 150 dpi in Grayscale. In other words, I just experimented without knowing what I was doing.

Bird

Harv · Jan 17, 2001

Muhammad -

Wait a minute, you sly dog!

I tried dropping my color depth to 4 and got the same results you did.

No wonder you're called the forum master. /w3tcompact/icons/wink.gif

Bird -
I think you're smarter than all of us. You got the job nicely done without wasting near as much time as I have. /w3tcompact/icons/smile.gif

Muhammad · Jan 17, 2001

My guess is you came out with a 222k GIF out of PS /w3tcompact/icons/wink.gif ... makes sense, because when you save an image as a GIF in PS, it is going to save it as a perceptual, selective, adaptive or greyscale; 256 colors. Take your pick, in this case it would be 256 shades of grey.

You can get away with only 2 colors if you adjust the image's brightness/contrast so the content is completely black, and so the two colors in the image would be white and black. The jump to 4 colors means another 15k, but the image looks as good to the average eye as the 256 color image does.

You need to reduce the number of colors in the GIF. PS6 has much better GIF and JPG image color/quality control than the 5.x versions... while I had plugins to do the work in 5.x, it can be done within Photoshop in 6.0.

markcg2000 · Jan 17, 2001

OK, I am no expert, but I think I meant something like that /w3tcompact/icons/blush.gif. I was trying to think that if Bird had scanned it telling the scanner it was a photo, then it would have a greater "color" range than a line drawing or text. Converting between formats, each succesive method would attempt to get as much information into the file as it could.

mark