Adobe Photoshop/Magic Wand Tool
The Magic Wand tool provides a means of selecting an area which contains a similar range of colors. For example, the tool can be used to select a shadowed area from an image since the region will generally contain a dark range of colors. Key to this process is the selection "threshold" which is used by the tool to determine the size of the color range used during the selection and thus how lenient the tool is in adding pixels to the selected area. A higher threshold indicates that more colors will meet the selection criteria and will generally result in a larger selected area.
To use the Magic Wand tool first select it from the Tool Bar. Then move your cursor into the area containing the color range that you would like to select; the shadow in our aforementioned example. Set the threshold to a value which you consider reasonable and click the mouse. Note that your threshold level selection will be a skill gained through experience and that you can always make multiple attempts at selecting an area and eventually tune the threshold correctly.
The following is a subset of options available when using the Magic Wand Tool;
- Anti-aliased: When enabled, the Anti-aliased forces the Magic Wand Tool to anti-alias the edges of the selection area.
- Contiguous: When enabled, the Contiguous option forces the Magic Wand Tool to select pixels that are directly connected together. So, if you wanted to select one shadow from a image enable the Contiguous option. But, if you want to select all shadows in the scene disable this option.