Paint

The old stand-by Paint utility is still included in the Accessories programs that come with MS-Windows, and provides an easy way to add simple tweaks and/or text annotations to your map images.

You can use Alt-PrintScr to copy an active ArcMap window to the Windows clipboard and then Ctrl-V to paste the image into a Paint window, then select and copy (Ctrl-C) just the map element into a new blank Paint window. Recent versions of Paint can save images in all of the standard graphics formats.

Paint is particularly good for pixel-by-pixel creation of small icons or logos that you might want to include in your graphics.

GIMP (Gnu Image Processing Program) is a freely-distributed image-editing program for PC's that includes virtually all of the functionality of Adobe PhotoShop. It has a master command window and one or more editing windows for graphic files.

You should generally edit your graphics in RGB mode. GIMP supports multi-layer images. If you add text annotations or other enhancements as additional layers to your base image, you will generally have to "flatten" the image into a single layer before saving it for display on the web.

GIMP includes a number of sophisticated filters for manipulating photos; these are definitely worth exploring.

XView is an old stand-by UNIX graphics editor suitable for doing last-minute edits, format conversions, etc. on your images after you have FTP'ed them to copland..  To use XView, start the Hummingbird Exceed X-emulator program on your lab machine.  Log into copland through the Exceed client.  (The Secure Shell SSH client is a text-only connection that doesn't support graphics.).  Then type "xv" at the copland shell prompt in the xterm window.

As with the other graphic editors, XView is most easily learned by simply playing with it. Click your right mouse button on the image to call up the main command window. Clicking your middle mouse button on the image selects the color at that pixel (the pixel location and RGB values are shown at the edge of the image).

XView's text annotation is pretty weak; GIMP's and even Paint's text annotation tools are better.

"Algorithms" include standard image-enhancement procedures such as blur, sharpen and edge-detect.

The Color Editor control screen (works for 8-bit images only) is accessed from the "Windows" button. If you want to convert images from 24-bit to 8-bit color, use the "Best 24=>8" option to get an adaptive palette.

The color editor window offers a pretty decent intro to color theory. The Colormap Editing Tool with 8-bit colormap display table and R, G and B adjustment dials to alter selected colors (the outlined box in the table). Click RGB/HSV to convert the RGB dials to HSV dials. The HSV Modification Tool lets you remap hues, remap white to add hue and saturation to white pixels in the image, adjust saturation, and adjust intensities by adding and moving various handles (the little boxes) that shape the intensity graph.

XView can read a wide variety of graphic file formats, and is useful for format conversions.  It even converts Postscript files to bitmapped images using Ghostscript (a shareware Postscript-like interpreter).