GIMP Select By Color Tool

A Look at the Select By Color Tool in GIMP

GIMP offers users a comprehensive range of selection tools, meaning that there should be an ideal tool suitable for just about every situation. The Select By Color Tool can make life very simple for you in cases where you want to select all the areas of an image that are the same color, perhaps to edit that color without affecting the rest of the colors in the image.

The Select By Color Tool is very similar in operation to the Fuzzy Select Tool, the main difference being that the latter only ever produces single continuous selections, whereas the Select By Color Tool will select all the areas in an image that are similar to the target color and so may produce multiple disconnected selections.



To use the Select By Color Tool, you just click on the image at the point of a color that you want to base your selection on and all of the pixels in the image that are similar to the color of the pixel that you clicked on will be selected. You can vary the size of the selection by clicking and then dragging the cursor to the right or downwards to increase the size of the selection, or dragging to the left or upwards to decrease the size.

The Tool Options contain a few possibilities for adjusting how the tool functions.

Mode

As with most of the selection tools, the Select By Color Tool offers four modes, defaulting to Replace the current selection. The other modes, Add to the current selection, Subtract from the current selection and Intersect with the current selection allow the Select By Color Tool to make multiple selections that are combined to make a more complex final selection. One example might be making selections based on two distinct colors.

Antialising

This gives the selection's edge a more natural appearance and is the preferred option in most uses. If this is deselected and you zoom in to look at a selection, its edge will appear to be harsh and blocky.

Feather Edges

This allows you to give a selection a very soft edge that gently blends out like a gradient.

When the checkbox is checked, a slider is displayed allowing you to adjust the amount of feathering applied.

Select Transparent Areas

This allows the selection to contain completely transparent pixels if they fall within the Threshold that has been set.

Sample Merged

This will only affect images with more than one layer where the target layer's Opacity is less than 100 or the layer's Mode is set to anything other than Normal. In that case, the appearance of the layer's colors may be affected by the layers below. If the Sample merged checkbox is checked, the selection will be based on the composite effect of all the layers, whereas if it is unchecked only the colors of the target layer will be used to form the selection.

Threshold

This determines how similar a color must be to the selected pixel before it is included in the selection. The further to the right the slider is set, the larger the final selection will be.

Select By

This drop down menu offers a few variations on how the selection is made. In most cases, the Composite option will be best, as that most closely matches what your eye sees, but there may be cases where you wish the similarity of color to be calculated on a specific aspect of the visible color.

The possible options are to match by Red, Green, Blue, Hue, Saturation and Value.

The Select By Color Tool can be a very quick and easy way to select areas of an image based upon their color, though its effectiveness can be largely dependent on the image that it is being used on.

Tutorial: Using GIMP's Select By Color Tool