While working on an image using GIMP, the first thing I noticed was the (100ms) at the end of the layer’s name, like the one below.
I really wonder what those numbers are. I didn’t even bother to search for an answer. I just want to finish what I have in mind – to put shadow.
With those numbers present:
I can use the tools particularly the eraser (my favorite) but not the Filter – Shadow (another favorite) was grayed out and all the other sub-menu entries.
Course of Action: Closed the program and open a bitmap that can be edited.
Another Day Came: Launched GIMP and read the tip of the day.
Tip: Not all effects can be applied to all kinds of images.
This is indicated by a grayed-out menu-entry.
You may need to change the image mode to RGB (Image→Mode→RGB), add an alpha-channel (Layer→Transparency→Add Alpha Channel) or flatten it (Image→Flatten Image).
Could that be the answer?