Since we've had a lot of new users join us in the last month or so, it's a good time to review our image rules. With a wiki of this size, we have had to enact several policies regarding the uploading and use of images. It's a good idea to review our various image policy pages, which can be found in the following places:
Technical tips from admins on how to compress images to required 100k without losing quality ( from a recent discussion elsewhere):
1) "Jpg images have a "quality" value. Just dropping that from 100 to 80 can cut in half the file size with no notable difference. Pixlr is a super easy to use free online tool that lets you do that, and almost all image editors should have that capability." Courtesy of PicassoAndPringles.
Comment: Preview on Mac OS X does not seem to have this capability.
2) "you should be able to accomplish the task easily with http://tinypng.com. (Although the site stresses its ability to shrink pngs, it also handles jpgs quite well.)" Courtesy of CzechOut
Preview is only the most basic of editing programs. As the name suggests, it's mostly there on an out-of-the-box Mac so that when you click on a file ending in .jpg or .png, you'll get something to display on your screen. You can do some basic resizing, but that's not really compression.
I don't know what your budget is, but there are a ton of options for you. You can get "proper" Photoshop for about $10/month. Or you could buy Photoshop Elements outright. Though I'm not sure of the price for students, it goes for $99 retail. (You could almost certainly buy an older, cheaper version on Ebay if that's too steep for you.)
There are any number of apps in the App Store which will offer genuine compression, so many that it would be laborious to list them all here. Just to give you a ballpark, though, things like Compress cost about $5.
Or you could do any of a number of free online compressors, like the one I mentioned above, or the even-easier-to-remember http://www.resize-photos.com.
↑As always, understand that no products or services mentioned here, or anywhere on this wiki, are warrantied in any way by, nor are they any sort of "official recommendation" of, either myself or Wikia. Any purchase or usage of any product mentioned are done at your own risk to your funds, computer, images or other personal property.