You may have an image of something with a pure white background, but you want that background to be transparent instead of white. Using Photoshop's selection tool, you can select only your image---without the white background---and transplant that image onto a transparent background. When working with transparency, it is important to remember that JPG files cannot support transparent backgrounds, so save your JPG file as a different image format such as GIF, TIFF, PNG or PSD.
Open the image file with the white background in Photoshop by going to the "File" menu and choosing "Open."
Click "Select" and then "Color Range." Change "Fuzziness" to 0 and next to "Select:" choose "Sampled Colors." With the colour picker, click the white background in your image.
Click the "Invert" check box in the selection window and click "OK." This will select everything in your image that is not white. Click "Edit" and then "Copy" to copy this selection to the clipboard.
Create a new Photoshop file by going to the "File" menu and choosing "New." Next to "Background Contents," choose "Transparent" and click "OK." Your file will have a checkered background, denoting transparency.
Click "Edit" and then "Paste" to paste your image onto your new file's transparent background.
Click "File" and choose "Save as." Save your new file as either a TIFF, GIF, PNG or PSD file.