There are a number of online sites that will let you upload ridiculously large image files, even those that are greater than HDTV resolution, even when they're going to be displayed as part of the site in sizes no more than 500 pixels across. Facebook's an example: Upload a picture that's 2500 pixels across, and it definitely will be scaled so people can see it. In fact, if it's shown in a size that's 500 pixels across, the image is really 5x what it needs to be, and should be reduced so that it's (far) faster for users to load.

But, as you say, how do you do that? Today I'm going to show you how to reduce a picture, photograph or other graphical image's size on the Mac by demonstrating the great shareware application GraphicConverter. It's shareware, so you can grab it and use it for free for a limited amount of time. After that, you'll want to pay the few dollars and get a license. In fact, I can wholeheartedly recommend GraphicConverter as it's the program I've used to edit graphics for Ask Dave Taylor for many years.

To start, grab a copy from Lemkesoft's Web site.

Now find an image you want to work with. I'll use a photo I took of the Universal Studios Hollywood CityWalk urban shopping area. To start, I'll view the Mac Get Info information by clicking once on the image's file icon, then pressing Cmd-I (cloverleaf-I). Here's what I see:

As you can see in the "More Info" area, this image is 1294x862. Let's say we need to reduce it to no more than 600px wide. That's a bit less than 50% of the current size.

Launch the freshly downloaded GraphicConverter, open the image file, and you'll see something like this:

A nice colorful picture, but it's too darn big. To shrink or reduce the image to a specific size -- I'll use a specific width of 600px, choose "Scale..." from the menu:

Now you'll be presented with a fairly large and complex dialog box, but in fact you only need to pay attention to the top segment, as shown here:

At this point you can indeed enter a specific pixel count for the width or height (if you don't have the lock bar between the measurements, btw, there's a checkbox on the page labelled "Proportional". Check it)

More interestingly, you can change the specific pixel count to a percentage, in case that's more how your mind works:

As soon as I type in "50" on the height percentage, the width in pixels is instantly changed. A 50% reduction produces a width that's 647px. Almost what we want, not quite. Instead, simply type in the desired width in the box as a pixel count:

Ready to commit? Click on "OK" and the image is quickly reduced to fit into the size parameters you've specified:

Now all you have left to do is save the image so you can upload the smaller, svelter version. Beware, though, if you just "Save" the file, the smaller version will overwrite the big version. If you're okay with that, no worries, but if you'd rather that didn't happen, use "File" -> "Save As..." instead.

Hope that helps. Now go upload something cool!