GIF Basics

1. GIF stands for Graphics Interchange Format. Originally, Compuserv Corp. developed this file type. Compuserv was a pioneer online community.
2. Many original, or source images are in TIF, JPG, BMP and EPS format and may have thousands or millions of colors. This is almost always true for true for color photographs.
3. A GIF Image can contain a maximum of 256 colors.
4. A GIF can have less than 256 colors.
5. If your Image has more than 256 colors before conversion to a GIF, PhotoShop will do it's best to "dither" or blend the original thousands or millions of colors to 256 colors. Photoshop uses sophisticated math to try to reproduce the look of the original image using only 256 colors.
6. Alternatively, original graphic art often contains less than 256 colors in the first place. A high impact graphic may have 16 colors or less! If this is the case, when the image is converted to a GIF it will retain it's original 16 color palette. The process will not "dither" the colors back up to a 256 color palette.

Image Format Notes

1. Please follow the same procedure outlined below to convert a JPG, TIF, PSD (photoshop document) or BMP image files to a GIF.
2. For all image formats, check Image > Mode > to verify that the image is in RGB Mode.
3. If you see Image > Mode > CMYK, change the mode to Image > Mode > RGB
4. If you have a gray scale or black and white photograph, you will want to change the Mode to Grayscale if it is not already there.

What to do if the image is already a GIF

1. If all you want to do is crop and/or reduce image size, you do not have to change the mode to RGB. You can crop or change image size directly in Indexed or GIF mode.
2. If the image is a GIF and you want to add text, work in layers, clean up the image or change some other deeper element, You must change the Mode from Indexed to RGB first.
3. If you do not do this, many of the Photoshop image adjustment tools will not work.
4. After manipulating the image, you will need to follow one of the two procedures below to change the image back to Indexed Mode followed by saving or exporting it as a GIF 89a.

If you are in a lab class, this image will be supplied by your instructor.

If you are viewing this page with a Web browser, to save the image above, place your mouse arrow on the above image and follow the instructions below.

1. Windows - right click on the image and select "Save Picture As." Save it to your local disk.
   
2. Macintosh - place your mouse arrow on the image, click and keep the clicker depressed, select "Save This Image As" and save the image to your local disk.

An image must be in the Indexed Color Mode BEFORE it can be saved as a GIF.

1. Open the parakeet image in PhotoShop
2. Open the "Image" menu and Select "Mode." Note that the JPG Image Mode is in RGB Mode.
3. Select Image > Mode > Indexed Color
   
   

The Indexed Color dialogue box will open next. The box below is from Photoshop 6.0. for Windows. The Mac dialogue box will be similar.

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Set up these settings in the dialogue box.

1. Palette drop down menu: Select > Adaptive.
2. Colors: leave the setting at 256 or what ever number is displayed. Photoshop will read the number of colors in the source image and display the correct number here.
3. Forced: select Primaries or Web.
   
   Primaries represent the RGB spectrum, or color gamut of the original image.
   
   Web refers to Web safe colors. Selecting Web adjusts the colors to make them display the same across different browsers & platforms. But, Web colors may change the image colors in ways you are not excited about. If this is the case, Primaries may look better. Experiment, save one each way, and if Web is acceptable, use it.
   
4. Transparency: accept this as it displays with or without a check box.
5. Options: Select > Dither > Diffusion
6. Amount: accept the default setting of 75%
7. Click on OK
8. The image is NOT a GIF yet. The image is now in Indexed Mode and ready to be saved as a GIF.

How to Save The Indexed Image as a GIF

1. Select File > Save As
2. Navigate to a directory to save the image in.
3. Locate the Format: drop down menu. Select CompuServ GIF from the list of image formats.
4. The GIF Options dialogue box will open next. Select > Interlaced. This will allow web page text to load before the image loads, holding your viewer's interest.
5. Click on OK

How to Reduce the Data Size of a GIF Image by removing colors.

1. If the "Colors:" setting is less than 256 colors because the original image has less than 256 colors in it, leave the setting as is. Do not try to increase the number of colors.
   
2. It may be possible to reduce colors in an image without hurting the quality. This is a good thing if you can do it. When you reduce or "strip" colors out of an image, you reduce file size. This contributes to faster download times. Experiment, nothing ventured, nothing gained.
   
3. If the Colors: box displays 256, change it to 128, or exactly half of 256. This will strip 128 colors out of the image reducing the kilobyte size of the file. Often times you can do this and not effect the quality of the image. The physical image size will remain the same, but the kilobyte size of the image will be smaller resulting in faster download time. Try 64 colors. This may be okay too. It all depends on the image.

Click here for a tutorial on how to make a "transparent GIF."

The dialogue box below is for Photoshop 4.0. for Macintosh. The Photoshop 4.0 for Windows dialogue box will be similar.

1. Palette drop down menu: Select > Adaptive.
2. Color Depth: Set at 8 bits/pixel. Usually, this is the default.
3. Colors: leave the setting at 256 or what ever number is displayed. Photoshop will read the number of colors in the source image and display the correct number here.
4. Options: Select > Dither > Diffusion
5. Click on OK
6. The image is now in Indexed Mode and ready to be saved as a GIF.

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