2.5. Fuzzy selection (Magic wand)

2.5. Fuzzy selection (Magic wand)
	2. Markeringsværktøjer

Figur 14.21. Magic Wand tool icon in the Toolbox

The Fuzzy Select (Magic Wand) tool is designed to select areas of the current layer or image based on color similarity.

When using this tool, it is very important to pick the right starting point. If you select the wrong spot, you might get something very different from what you want, or even the opposite.

The Wand is a good tool for selecting objects with sharp edges. It is fun to use, so beginners often start out using it a lot. You will probably find, however, that the more you use it, the more frustrated you become with the difficulty of selecting exactly what you want, no more, no less. More experienced users find that the Path and Color Select tools are often more efficient, and use the Wand less. Still, it is useful for selecting an area within a contour, or touching up imperfect selections. It often works very well for selecting a solid-colored (or nearly solid-colored) background area.

Note that as the selected area expands outward from the center, it does not only propagate to pixels that touch each other: it is capable of jumping over small gaps, depending on Threshold option. To increase/decrease Threshold, during the use of Fuzzy Selection, after the first button-press, dragging the pointer downward (or to the right) or upward (or to the left).

2.5.1. Activating the tool

You can access the Magic Wand Tool in different ways:

From the image menu bar Tools → Selection Tools → Fuzzy Select,
by clicking on the tool icon in the ToolBox,
by using the keyboard shortcut U.

2.5.2. Key modifiers (Defaults)

The Fuzzy Select tool does not have any special key modifiers, only the ones that affect all selection tools in the same way. See Afsnit 2.1, “Common Features” for help with these.

2.5.3. Tool handling

Figur 14.22. Using Magic Wand tool: selected pixels are contiguous

It starts selecting when you click at a spot in the image, and expands outwards like water flooding low-lying areas, selecting contiguous pixels whose colors are similar to the starting pixel. You can control the threshold of similarity by dragging the mouse downward or to the right: the farther you drag it, the larger you get the selected region. And you can reduce the selection by dragging upwards or to the left.

You can move the selection outline using Alt + arrow keys.

2.5.4. Indstillinger

Figur 14.23. Tool Options for the Magic Wand tool

Normalt vises værktøjsindstillingerne i et vindue under værktøjskassen, så snart du aktiverer et værktøj. Hvis de ikke gør, kan du få adgang til dem fra billedmenulinjen via Vinduer → Dokbare vinduer → Værktøjsindstillinger, som åbner indstillingsvinduet for det valgte værktøj.

	Bemærk
	See Selection Tools Options for help with options that are common to all these tools. Only options that are specific to this tool are explained here.

Mode; Antialiasing; Feather edges: Common select options.

Find ens farver

These options affect the way the Magic Wand expands the selection out from the initial point.

Select Transparent Areas

This option gives the Magic Wand the ability to select areas that are completely transparent. If this option is not checked, transparent areas will never be included in the selection.

Udtag prøve forenet

This option becomes relevant when you have several layers in your image, and the active layer is either semi-transparent or is set to another Layer Mode than Normal. If this is the case, the colors present in the layer will be different from the colors in the composite image. If the “Sample Merged” option is unchecked, the wand will only react to the color in the active layer when it creates a selection. If it is checked it will react to the composite color of all visible layers. For further information, see the glossary entry Sample Merged.

Diagonal Neighbors

When activated, the tool considers diagonally neighboring pixels as connected when calculating the affected area. In other words, instead of looking at the four orthogonal neighbors of each pixel, it looks at all eight pixels

Figur 14.24. Example for Diagonal Neighbors

A pixel with 4 orthogonal neighbors

A pixel with 4 diagonal neighbors

A pixel with 8 neighbors

Figur 14.25. Example for Diagonal Neighbors option applied

Diagonal Neighbors option unchecked

Diagonal Neighbors option checked

Tærskel

This slider determines the range of colors that will be selected at the moment you click the pointer on the initial point, before dragging it: the higher the threshold, the larger the resulting selection. After the first button-press, dragging the pointer downward or to the right will increase the size of the selection; dragging upward or to the left will decrease it. Thus, you have the same set of possibilities regardless of the Threshold setting: what differs is the amount of dragging you have to do to get the result you want.

Select by

This option determines which component of the image GIMP uses to calculate the similarity in color.

You can choose from Composite, Red, Green, Blue, Alpha, HSV Hue, HSV Saturation, HSV Value. LCh Lightness, LCh Chroma, and LCh Hue.

Draw Mask

This option can help to visualize the selection. Selected areas marked with marching ants may not be evident when selecting with Fuzzy select or Magic wand. If this option is checked, selected areas will be filled with a magenta color as long as you keep pressing on the left mouse button, and this mask will disappear as soon as you release this button.

Figur 14.26. Example for Draw mask option applied

Fuzzy Select used with Draw Mask option unchecked

Fuzzy Select used with Draw Mask option checked, left mouse button not released yet.