Converting to indexed color (Photoshop)

Converting to indexed color reduces the number of colors in the image to at most 256--the standard number of colors supported by the GIF and PNG-8 formats and many multimedia applications. This conversion reduces file size by deleting color information from the image.

To convert to indexed color, you must start with either a grayscale or RGB image.

To convert a grayscale or RGB image to indexed color:

1. Choose Image > Mode > Indexed Color.

Note: All visible layers will be flattened; any hidden layers will be discarded.

For grayscale images, the conversion happens automatically. For RGB images, the Indexed Color dialog box appears.

2. Select Preview the Indexed Color dialog box to display a preview of the changes.
3. Specify conversion options. (See Conversion options for indexed-color images (Photoshop).)