The filters in certain menus are available only in 16 million colors without the
transparency option because most of them recompute and modify the colors.
For example, they are disabled for GIFimages and images in indexed colors
mode. If you do not have access to these menu item filters, perform the
following operations:
• Select the menu item "Image / Transparent color" (in situation of an image
with a transparent color) then click on the option "Disable transparency"
• Select the menu item "Image / Mode / RGB color"