Hi all I'm a noob to ATS but I have something for you.

Originally posted by ArMaP
No, you can't recreate the original from the image saved with less colours, regardless of compression.

And this is why I object to people calling GIF a lossless compression format without qualifying it. I said at least 3 different times in my post that it was for less than 256 colors but you seem to want to ignore this is a narrow exception these days, since many things have more than 256 colors.
I don't know of any option in GIF to compress it with more than 256 colors. And even though most of the internet is wrong in not listing the qualifier in the lossless claim, I found a site that does state it correctly, the claim of lossless GIF needs to be qualified exactly like this site does, it's one of the few sites that properly qualifies the lossless claim:

www.ou.edu...

GIF: Lossless for images

Originally posted by Arbitrageur

www.dictionarist.com...

English - Definition of dark side of the moon :
section of the moon that is hidden by the light of the sun

It seems St Exupery was right after all. (he usually is, btw).

Hidden by the light of the Sun? Say what?

Wow. Love what you did with the image. I have a couple of questions why do the smaller craters look convex rather then concave like the bigger craters do? Also is there an application for windows that could clean that image up to the same standard as you achieved with Isis?

Originally posted by Phage
Hidden by the light of the Sun? Say what?

Maybe they meant "from"

Perhaps this is better:

The side of the Moon that faces Earth is called the near side, and the opposite side the far side. The far side is often called the "dark side," but in fact, it is illuminated as often as the near side: once per lunar day, during the new Moon phase we observe on Earth when the near side is dark.

The English language isn't lacking in misnomers, and calling the far side the "dark side" is a good example, since the far side isn't any darker than the near side.

reply to post by AusiAnarchist


Smaller craters may have the shadows fully traverse the entire crater. On the other part you won't get good free software to manipulate or diagnose images especially from Windows. End of conversation.

You can't 'clean up' images with the original resolution absent. There are however several digital 'actions' one can purchase for quick Photoshop automatic image sharpening tools. They however cannot sharpen a blurry overall image. (This is not what places like NASA would use). Fred Miranda has relatively inexpensive action plugins for Photoshop actions. The problem is that when you do purchase one of his many 'Digital Darkroom' application actions, it is specifically written to a single version of Photoshop, and when you upgrade they are worthless and cannot be installed or used.

I and my colleagues have used Miranda Digital Darkroom before and bought many of the individual 'actions' and traded them under the table but when we had to upgrade Adobe, like many things written for Adobe, they don't work anymore, unless you buy more, and more, and more....well, you get the picture of the Premiere digital software industry focus is to get you to continue buying and we just won't unless a client pays for it.

Miranda Digital Darkroom is likely still the best software actions you can get, if you have Photoshop. If you don't you are just throwing darts and seeing what sticks.

Originally posted by Arbitrageur
And this is why I object to people calling GIF a lossless compression format without qualifying it.

There's no need for "qualifying" it, and I didn't ignored what you said, the problem is that you are calling two different things by the same name.

When you apply the compression in GIF, it doesn't matter if it has 256 colours or just one, the compression is always lossless.

The fact that GIF files can only have a maximum of 256 colours is a limitation of the format, not of the compression algorithm, in the same way JPEG is limited to a maximum image size of (I think) 65500 pixels or can "only" use 8 bits per channel.

Sorry for being insisting on it, but being used to read file specifications and having created a compression method myself, I know that I am talking about two different things.

reply to post by Illustronic


Well I found Nasaview that lets me view PDS images from their catalogue and save them as GIF, GIF AS "what ever that is:, JPEG and JPEG AS. However there are not many editing options.

reply to post by AusiAnarchist


"Save GIF as" and "Save JPEG as" let you chose the place where you want to save the images, while "Save GIF" and "Save JPEG" save the image in that format on the same folder as the original.

Originally posted by ArMaP
When you apply the compression in GIF, it doesn't matter if it has 256 colours or just one, the compression is always lossless.

You don't say what happens if there's more than 256 colors. We've already agreed it's lossless if it has 256 colors or less.

The fact that GIF files can only have a maximum of 256 colours is a limitation of the format, not of the compression algorithm

Regardless of what is causing the limitation (the "format" or the "compression algorithm") if the original image has more than 256 colors, the GIF file cannot be called "lossless" because you can't recreate the original image from the GIF file.

But we agree it's lossless if and only if the original image has 256 colors or less.

reply to post by Arbitrageur


It's not the format that's lossless, it's the compression algorithm that's lossless.

reply to post by ArMaP

As long as you agree that the GIF file is NOT a lossless version of the original image with 257 or more colors, I can live with that explanation.

reply to post by Arbitrageur


I agree, regardless of file format, a 256 colours version of a 257 (or more) colours image always represents a loss of data.