Select Image File Dialog, Image Section
|Current Color Palette|| If on, the active color table is imposed on the imported image.
If off, the optimum colors for the imported image are computed and appended to the end of the active color table. A maximum of 240 colors are appended, leaving the first 16 colors in the color table intact.
|Transparent Background||If on, the image's background — defined as all pixels with the same color as the upper left-most pixel — is transparent.|