Converting JPG to GIF or PNG (Reducing File Size)

I’ve downloaded many very simply images (in the public domain, of course) that were surprisingly JPGs, rather than PNGs or GIFs. I assume they were created by people who didn’t know what they were doing, as the file sizes are often ridiculously big.

For example, I recently downloaded a map that consists of just three colors - the background color, black (text and national borders) and the color red indicating an animal’s distribution. The file size should be less than half than what it is.

But when I copy it into a new Photoshop document, then try and save it as a GIF or PNG, the file size is still big, sometimes even bigger.

So, is there a way to convert such images to PNG/GIF and reduce the file size? Though I’ve used Photoshop for a long time, I’ve never really mastered the details, so there may be a simple solution(s) I simply haven’t stumbled over yet.

Incidentally, I’m using CS3.


Maybe these would help:

The problem is how JPG compression works. If you have had these originals you would experience such issues.

JPG makes 250something different artifact patterns and compresses based on those. So although you may perceive only 3 colors there are actually many more. ( thsi makes magic wand selection of JPGs a b*tch too, BTW). You may need to edit the color table of the GIF/PNG(that gives you more control)… or for a rough idea POSTERIZE to 3 colors (or however many you perceive) then save for web.

ALSO, in the case of PNG24 , note that the format adds an extra layer even w/o any transparent or semi-transparent pixels, and one which PS wont remove :(. You may need a separate utility for that. But if your image doesn’t require semi-transparency consider gif/png8 as a format and editing the color table down.

I wasn’t even aware of Photoshop’s Posterize function; that should be a big help. I’ll check out your links, too, logic earth. Thanks for the tips!

well, you could always use a free image editor, i peronally used irfan’s editor to batch convert files, but if you can afford it, you can go with photoshop too…i guess…

@Mae Rose

The latest Photoshop CS6 Beta is for free - only about 1.6 gig download :slight_smile: I do not know if the beta version is free forever or is limited.

Check out!

Photoshop has a wonderful option available File->Save for Web or using the shortcut: Alt+Shift+Ctrl+S

Numerous options are available and each selection has a preview with associated file size along with estimated time to save at a particular baud rate.

Once it gets out of beta and into normal-ness, it’ll be commercial.