what is Opaque source pixels?

[Cxlung12345]

I tried to select an area in a photoshop layer and the fill the area with a different color but a dialog box says "Could not fill because there are not enough opaque source pixels"  What does it mean? how do I fill color in a selected area?

[JJMack · Accepted solution]

Menu Edit>Fill the Fill Dialog has many options which were you using. Paintbucket tool.  Paint Brush. many ways to fill an area which way were you using when you recieved that message?

[Cxlung12345]

Thanks for the answer. I used the "Fill" from the Edit drop-down menu and get the "not enough Opague Source Pixel" message. After seeing your response, I used the paint brush too instead. It worked then. But I don't understand why the "Fill" command from the Edit menu is the problem. Any idea?