Opacity increasing

Any ways to increase the opacity of the pixels if it is not fully opaque?

So I wanted to outline inside a picture so that its borders can be removed. However, it always fails because there are some pixels in the picture where it is not fully opaque. Is there any way to work around with this? I tried copy and pasting the same picture above itself, but it is still imperfect.

*Edit: Nvm, found the Transparency thing.