A familiar tool for those with experience from graphics editors, the magic wand tool lets you quickly select parts of an image with a specific colour. It works by looking at your original selection and then finding similar pixels in colour and proximity to the original.
The magic wand can be selected by clickingor by pressing “W”.
There are multiple ways to use the magic wand. You can left-click or press “A” on any part of an image where you would like to use the magic wand. If you do so, an area will be selected. This selection area depends on your settings for the tolerance modifier.
You can also left-click, hold, and drag the mouse pointer to any direction. If you do this, you will see parts of the image going red. This is your potential selection area and it will change depending on how far away the mouse pointer is from where you first clicked. By moving the mouse pointer away from the starting point, your tolerance setting and selection area will increase. Moving the pointer closer to the starting point will shrink tolerance as well as the selection area. When you are satisfied with your selection area, you can release the left mouse button.
In some cases where you want to select more complex objects, you might need to use the magic wand multiple times. To do so, you need to add a new selection to your existing selection. This is easily done by pressing and holding “shift” while using the magic wand or by pressing the in the tool settings toolbar.
You can also subtract from your current selection using the magic wand. To do so, press and hold “alt” while using the magic wand or press in the tool settings toolbar.
If you are unhappy with your selection and want to start over, you can either press “esc”, “backspace”, “del”, or “fn” + “del”.
When you are satisfied with your selection you can turn it into an object by pressing “enter”, or by clicking the “Convert” button in the tool settings toolbar.
The tolerance level controls how similar in colour surrounding pixels need to be to be selected when you click on one pixel. A high tolerance will mean that only pixels that are very similar in colour will be selected. A low tolerance will lead to more pixels of varying colours being selected.
The tolerance modifier can be changed by using the slider menu in the tool settings toolbar. You can also adjust the tolerance with your keyboard. Pressing “,” will decrease tolerance, and pressing “.” will increase tolerance.
As the magic wand tool by default create masks, sometimes you will get a selection with unwanted holes in it. To remove those holes, we have the "fill closed path" button that can be found in the tool menu (top of screen). By clicking this button, you tell the tool to take the current selection, and then creating a uniform, complete object out of the current selection.
If you are working on simple images where you have one object to annotate per image the "Invert mask" button might be of help. What this button does is to take everything not selected using the magic wand and then selecting that, while deselecting everything that was previously selected.