The Color Picker Tool is used to select a color on the active layer. By clicking a point on a layer, you can change the active color to that which is located under the pointer. The Sample Merge option lets you grab the color as it is in the image, resulting of the combination of all layers.
You can get to this tool in several ways :
In the image menu through
→ ,by clicking the tool icon in Toolbox,
by pressing the O keyboard shortcut,
by pressing the Ctrl key while using a paint tool. The Color-picker dialog is not opened during this operation and the tool remains unchanged after releasing the key.
The o key will activate the Color Picker tool.
By pressing the Shift key, the Add to palette option is temporarily checked.
The available tool options for the Color Picker can be accessed by double clicking the Color Picker tool icon.
The Sample Merged checkbox when enabled will take color information as a composite from all the visible layers. Further information regarding Sample Merge is available in the glossary entry, Sample Merge.
The Radius slider adjusts the size of the square area that is used to determine an average color for the final selection. When you click the layer, the cursor will indicate the size of the square or radius visually.
The color of the selected pixel will be shown in an Information Dialog, but not otherwise used.
The Foreground color, as shown in the Toolbox Color Area, will be set to the color of the pixel you click on.
The Background color, as shown in the Toolbox Color Area, will be set to the color of the pixel you click on.
When this option box is checked, the picked color is sent to the active color palette. see Palette Editor