Gimp’s Select by Color tool shares many aspects with the Fuzzy Select tool and together these tools will be seen by many Adobe Photoshop users as a direct equivalent to the Magic Wand tool.
A simple explanation of the tool is that it selects areas of an image that are within a similar color range. Unlike the Fuzzy Select tool, the Select by Color tool will select disparate areas that are not physically connected, so the tool may result in more than one selection.
The tool has a few settings that can affect how the tool works and the type of selections that it makes.
Selection Modes of the Select by Color Tool
The Select by Color tool shares its selection modes with most of the other selection tools. The default is Replace the Current Selection which will only ever allow a Designer to make a single selection, cancelling any other live selections. Add to the current selection allows the addition of further colors to a selection and if the selection goes too far, the Subtract from current selection mode can be used to remove areas from the selection.
The final selection mode provides the power to combine two selections into a single selection that contains only the colors that are common to both selections.
Settings of the Select by Color Tool
Below the selection mode buttons, there are a number of other settings, starting with antialiasing. This makes the edges of selections softer and more natural by reducing the opacity of those pixels, so that visually the selection will blend more naturally into an image.
The Feather edges setting opens up a slider when the checkbox has been clicked which allows the Designer to adjust the radius of the feathering to give a harder or softer edge to the selection. Unlike antialiasing which acts only on the edges of the selection, Feather edges can affect many more pixels, depending on how the slider is set.
Select transparent areas is turned on by default and allows transparent pixels to be included within a selection, though in some cases it maybe useful to uncheck this box prior to making a selection.
Sample merged defaults to off, but when turned on it selects pixels from all visible layers, rather than just the active layer. The Threshold slider sets how similar colors need to be before being selected and so when this is set to a higher number, more colors will be selected if they are present in the image.
The final option is the Select by setting which affects how pixels are selected. The default setting of Composite selects pixels in a similar way to the human eye, but it can also be used to select pixels that are similar in only one color channel or by HSV.
The Select by color tool in Gimp can be used on its own or in concert with the other selection tools to make complex selections.