The Fuzzy Select tool in Gimp is similar to the Magic Wand in Adobe Photoshop, though the main difference is that Gimp also has the Select by Color tool which operates in similar way, meaning that Gimp has two tools where Photoshop has one.
The difference between Fuzzy Select and Select by Color is that Fuzzy Select only selects contiguous parts of the image based on color, whereas Select by Color selects similar areas across the whole image.
In practice this means that Fuzzy Select will only select similar areas that are joined and the result will be a single selection, while Select by Color may result in multiple selections within the one image.
Other than that difference, the two tools are much the same in use.
Why Use the Fuzzy Select Tool
The main strength of the Fuzzy Select tool is that it can make selections within an image that would be difficult, and often impossible, for a Graphic Designer to make manually. The tool selects parts of an image that are similar in color and so can make selections that look quite natural.
If an image contains an irregularly shaped object on a contrasting color background, the Fuzzy Select tool can be used to quickly select the background and, perhaps, change its color or remove it completely.
The weakness of the Fuzzy Select tool is that it only recognises colors and not objects, so if the object and the background share similar colors, parts of both may be selected and the two parts may not be easily separated using this selection tool.
Options for the Fuzzy Select Tool
Graphic Designers who are comfortable using the other selection tools that are available in Gimp will immediately feel comfortable with most of the options available with the Fuzzy Select tool.
There are four mode options that can be used to produce more complex selections.
The Replace the current selection will only ever allow a single selection to be made. Using Add to the current selection allows Designers to select different colors and build up a more complex selection. Subtract from the current selection offers the option of removing a certain color range from an existing selection and the final mode, Intersect with the current selection will produce a selection that only includes areas that are common to two selections.
Antialiasing is turned on by default and means that the selection will have a softer more natural feel around its edges, meaning that any manipulations carried out on the selection should appear less obvious.
Feather edges produces a selection with an edge that fades out to transparent and when selected, a slider becomes visible to allow the degree of feathering to be selected. In practice, if a feathered selection is filled with a solid color, the edges of the resulting shape will appear very soft and this can be used to good effect, such as in dreamlike images.
The Select transparent areas option defaults to on and allows a Designer to select areas that are completely transparent. In some cases, turning this off may make it easier to make an accurate selection.
Sample merged defaults to off and when turned on allows the Fuzzy Select tool to select similar areas across all visible layers, rather than just the active layer.
The Threshold slider sets the sensitivity of the selection tool and can be set from 0 to 255. The higher the number, the more colors will be selected when Fuzzy Select is used. Choosing a lower number means that only colors that more closely match the selected will color will be included in the resulting selection. Often a Designer will have to adjust this setting by trial and error in order to achieve the desired selection.
The final option is Select by. In most cases Composite will be the best choice as this selects colors on the basis of how the eye sees them, but there may be occasions when making a selection based on individual RGB or HSV values, yields a better result.
The Fuzzy Select tool is a powerful selection tool in its own right, but when combined with the other available selection tools available in Gimp, some very complex selections can be made to allow Graphic Designers to edit very specific parts of an image.