HVS ColorGIF 2.0 User Manual

[ Contents | Digital Frontiers ]

Using Selections

HVS ColorGIF operates on RGB images. The package includes both Filter and File Export versions of the plug-in, because each of these formats excels at particular tasks. One of the major differences is how the two handle selections. The Filter version of ColorGIF is able to work with selections and individual layers in the RGB image, whereas the Export plug-in isn't provided selection information by the host under the Photoshop 3.0 plug-in standard.

For example, let's say you want to use parts of a screen shot as images embedded in an HTML manual (like this one). Normally this would be a tedious procedure of cutting and pasting and creating many images in the paint program. With the ColorGIF 2.0 filter, all you need to do is draw a selection around the part of the image you want to save as a GIF. When ColorGIF comes up, the preview will show only the selected area. You can do a reduction and save the selection as an independent GIF with a couple of keystrokes. You can even create one Adaptive palette for the whole screen shot, and then save it and bring it in as a fixed palette. Once you get the parameters set the way you want them, just draw the selection and hit Cmd-F and a GIF will be saved automatically. See Batch Production for more details on using the filter in this way.

Another use of selections is to handle different areas of an image in different ways. Let's say you have a banner with a complex foreground image against a background of flat color. You want to use some dithering on the foreground to improve the gradients, but you want to leave the background untouched because it's already the exact color you want, and you might need to make it transparent. Here's the procedure:

  1. Using the Magic Wand tool, select the foreground image only. The easiest way to do this is probably to click in the background and then Invert Selection).
  2. Invoke HVS ColorGIF filter, and you will see only the selection against a blue background (the blue is used to represent unselected regions in a non-rectangular selection).
  3. Select the Dithering Intensity and number of colors appropriate for the foreground. When you are happy with the preview, hit Apply to apply the reduction to the original RGB image.
  4. You will now have a color-reduced foreground region, and the background will remain untouched. Deselect and invoke the filter again.
  5. You should now see the number of colors in the RGB image in the Colors Used status line, and Exact showing in the Palette popup. (This assumes that your background didn't have enough colors to make the total more than 256). You can now save the whole image as a GIF.

Another great application of selections is reducing different parts of the image to different color depths. By using color range and magic wand selections in your paint application, you can color-reduce each region individually, using Apply each time to apply the result to the RGB image. For example, you might have a troublesome gradient that needs a large number of colors to look smooth. Reduce the gradient indendently, and when you're done with the whole image go in and either save from the Exact palette or reduce the palette further using Custom. The Custom reduction algorithm applies HVS technology to determine the best combination of a smaller number of colors, and is extremely effective at reducing existing palettes even further.

For more information on this topic, see the sections on dithering, color depths, and creating a MultiPalette.