Basic GIMP'ing; resizing an image with a few options

Resizing an image is a very common task and The GIMP as all you need a more to do this.
In this post I will assume that you already have The GIMP installed. If not yet, you can find the relevant installation information on The GIMP web site and follow the respective platform installation. You can get The GIMP and find all the information about it on it's dedicate web site and at many other place on the Internet like the official English GIMP user group (GUG). Just Google 'The GIMP' and you'll see how much information you can find about the GIMP.
The GIMP is free; both as "it cost nothing" and as in freedom. It's an Open source project under the GNU General Public License!

So here's the basic screen you get with a picture open with the GIMP. By default, three windows a loaded organizing the tools sets. The image is open in it's own windows. You can have more than one image open at once. It may be new to you to have this kind of windows organization but you should soon realize that when you work on images, you want all the space you can.



Before going further, once again, save your work on a different name. ALWAYS work on copy whenever you can so you don't mess up the original... safety first.





If you expand the saving menu, you get an enhanced interface...



Many file formats offer various options; in this case JPEG (*.jpg) has it's own. You can use the default setting but I find 'Progressive' option to be nice for web publishing. This option refer to the way the image is loaded by the Internet browser; non-progressive images open at full resolution from top to bottom while progressive start to load at low resolution but full size in the page. If you click on the images on this post, you'll see that I've saved those images with the 'Progressive' option checked.
The other "option" worth to mention is the 'Quality' slider on top. You can reduce the image size in term of disk space by sliding to the left. Check the 'Show Preview in image window' to see in real time the effect of the quality option slider. Of course, the more you slide to the left, the smaller your image file size will be but the image will start to loose it's resolution. I generally slide between the default (85) and 50 with the 'Show Preview in image window' checked to see how it look.



Now we're ready to make the resizing of the image. On the image's window menu, use the 'Image' menu to reach the 'Scale image...' dialog.



That will produce a dialog where you can specify all the size parameters, including Height, Width, and XY resolutions. Note the bit of chain next to the Width and Height boxes. You can click on that to link or unlink the height and width values. If the chain is intact, then the aspect ratio will be preserved. Let's assume that your image is 1280x960 pixels (4:3 aspect ratio). If you change the Width to 640, then the Height will automatically change to 480 (still 4:3) when you leave the Width box (by tabbing out or clicking another box). If you break the chain, by clicking on it, then you could make your image 640x500 (not 4:3), if you wished.



That conclude this post about resizing an image in The GIMP. The inspiration was to help some friends with their images publishing on forums. While at it why not introduce to some basic optimizations too!?
A lot more should (could) be covered about images formats, optimizing, web publishing and options related to their respective formats and I may very well post some more about using The GIMP for those.
There are a few more nice things I plan to post about using The GIMP such as nice way to watermark your images, image manipulations such as red eye removal and touch up of pictures and a cool one I recently learn about is making people Jedi knight (kids love that one)... stay tuned!

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Thanks to Denver Hull for his contribution on this post. Bot on Denver!