Today I will talk about a little used selection method. We all know the 4 selection tools - rectangle, ellipse, free (aka lasso) and fuzzy (aka magic wand). Quick tip for the fuzzy select - if you hold down Shift, you can select further pixels/areas without losing your original selection.
If you look in the Select menu you will see some others - by color and from path. There is however another method that you might find useful. It is right at the bottom of the Select menu - Quick Mask. In all probability you will never access it through that menu.
Here’s how you use it. Before activating the Quick Mask you need to have one of two tools already activated (brush or eraser) and the foreground/background colours need to be set to black and white. To illustrate how this is used, I have made a quick little drawing. Please be aware that these images are done quickly just to illustrate this method. You can do much better.
And here is that little picture in a gimp window/workspace.
So why essentially show you the same thing twice? Well this second image shows you the way to access a Quick Mask quickly. Look in the bottom-left corner of this window, on the same level as the horizontal scroll-bar. You will see a tiny square made from broken lines. Clicking this square toggles the Quick Mask on (alternatively press Shift+Q).
Not only is the Quick Mask now activated but the little square is now made whole and coloured red. Now we will erase some of this red coloured overlay. You can use either the brush tool or the eraser tool to do this. With the brush tool, white erases and black will re-paint the red overlay wherever you paint. With the eraser tool the colours are reversed. In other words you can correct any errors you make. So let’s start…
I am using the brush tool but you get the same result when using the eraser tool.
Once you have done it will look something like this. Now we toggle the Quick Mask off…
Voila. The area that you cleared is now automatically selected. The thing is you can clear more than one part of the image at once and you can toggle the Quick Mask on and off at will until you are satisfied. OK, let’s clear the background. First invert the selection.
Now let’s do color to alpha and
Remember, it may be called a mask but in practice it is a versatile method to select an arbitrary number of areas of an image. Also, this last image does not really relate to the preceding ones (I had an accident and needed to redo quickly).