I hope one of these if not all may be able to help you out.
Mapping colors to transparency
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You can add transparency to an optimized image by mapping existing colors to transparency.
To map colors to transparency:
Select one or more colors in the optimized image or color table. (See Selecting colors.)
Do one of the following:
Click the Map Transparency button in the Color Table palette.
Choose Map Selected Colors to Transparent from the Color Table palette menu.
The transparency grid appears in half of each mapped color. The small square at the lower right of the color swatch indicates that the color is locked.
To revert transparency to its original colors:
Do one of the following:
Select the colors you want to revert, click the Map Transparency button or choose Unmap Selected Colors from Transparent from the Color Table palette menu.
To revert all transparency-mapped colors, choose Unmap All Transparent Colors.
Specifying the gradient transparency
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Each gradient fill contains settings that control the opacity of the fill at different locations on the gradient. For example, you can set the starting color to 100% opacity and have the fill gradually blend into an ending color with 50% opacity. The checkerboard pattern indicates the amount of transparency in the gradient preview.
To specify the gradient transparency:
Create a gradient as described in steps 1 through 10 of Creating smooth gradient fills.
To adjust the starting opacity, click the left opacity stop above the gradient bar. The triangle below the stop turns black, indicating that the starting transparency is being edited.
In the Stops section of the dialog box, enter a value in the Opacity text box, or drag the Opacity pop-up slider.
To adjust the opacity of the endpoint, click the right transparency stop above the gradient bar. Then set the opacity as described in step 3.
To adjust the location of the starting or ending opacity, do one of the following:
Drag the corresponding opacity stop to the left or right.
Select the corresponding opacity stop, and enter a value for Location.
To adjust the location of the midpoint opacity (the point midway between the starting and ending opacities), do one of the following:
Drag the diamond above the gradient bar to the left or right.
Select the diamond and enter a value for Location.
To delete the opacity stop you are editing, click Delete.
To add an intermediate opacity to the mask, click above the gradient bar to define a new opacity stop. You can then adjust and move this opacity as you would for a starting or ending opacity. To remove an intermediate opacity, drag its transparency stop up and off the gradient bar.
To create a preset gradient, enter a name in the Name text box and click New. This creates a new gradient preset with the transparency setting you specified.
Using the color table to edit colors and assign transparency
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You can edit colors in the color table to produce special effects, or assign transparency in the image to a single color in the table.
To edit colors in the color table:
Open the indexed-color image.
Choose Image > Mode > Color Table.
Click or drag in the table to choose the color or range of colors you want to change.
Choose a color, as explained in Using the Adobe Color Picker, and click OK.
If you are changing a range of colors, Photoshop creates a gradient in the color table between the starting and ending colors. The first color you choose in the Color Picker is the beginning color for the range. When you click OK, the Color Picker reappears so that you can choose the last color in the range.
The colors you selected in the Color Picker are placed in the range you selected in the Color Table dialog box.
Click OK in the Color Table dialog box to apply the new colors to the indexed-color image.
To assign transparency to a single color:
Choose Image > Mode > Color Table.
Select the eyedropper, and click the desired color in the table or in the image. The sampled color is replaced with transparency in the image.
Using image clipping paths to create transparency
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You may want to use only part of a Photoshop image when printing it or placing it in another application. For example, you may want to use a foreground object and exclude the background. An image clipping path lets you isolate the foreground object and make everything else transparent when the image is printed or placed in another application.
Image imported into Illustrator without image clipping path, and with image clipping path
To save a path as an image clipping path:
Draw a work path that defines the area of the image you want to show. For more information, see Creating a work path (Photoshop) and Converting selection borders to paths.
Note: Paths are vector-based; therefore, they have hard edges. You cannot preserve the softness of a feathered edge, such as in a shadow, when creating an image clipping path.
In the Paths palette, save the work path as a path. For more information, see Managing paths (Photoshop).
Choose Clipping Path from the Paths palette menu, set the following options, and click OK:
For Path, choose the path you want to save.
For Flatness, leave the flatness value blank to print the image using the printer's default value. If you experience printing errors, enter a flatness value to determine how the PostScript interpreter approximates the curve. The lower the flatness value, the greater is the number of straight lines used to draw the curve and the more accurate the curve.
Values can range from 0.2 to 100. In general, a flatness setting from 8 to 10 is recommended for high-resolution printing (1200 dpi to 2400 dpi), a setting from 1 to 3 for low-resolution printing (300 dpi to 600 dpi).
If you plan to print the file using process colors, convert the file to CMYK mode. For more information, see Converting between color modes (Photoshop).
Save the file:
To print the file using a PostScript printer, save in Photoshop EPS, DCS, or PDF format.
To print the file using a non-PostScript printer, save in TIFF format and export to Adobe InDesign or to Adobe PageMaker® 5.0 or later.
Note: If you import an EPS or DCS file with a TIFF preview into Adobe Illustrator, the image clipping path transparency may not display properly. This affects the on-screen preview only; it does not affect the printing behavior of the image clipping path on a PostScript printer.