The Extract command in photoshop provides a sophisticated way to isolate a foreground object from its background. Objects with intricate or wispy edges can be selected quickly in a way that would be impossible to do using the selection tools. Here’s how to do it;
1. Open an image in Photoshop. I’m using a beautiful picture of a gorilla taken by PaulMT and available on Stock Exchange for free download.
2. Choose Filter > Extract.
The Extract dialog box appears with the edge highlighter tool () selected in the upper left area of the dialog box.
To extract an object, you use the Extract dialog box to highlight the edges of the object. Then you define the object’s interior and preview the extraction. Applying the extraction erases the background area to transparency, leaving just the extracted object. (in theory!!)
3. Choose a brush size for the highlighter. This will vary from subject to subject, but for the gorilla image, try about 35 in the Brush Size text box. It’s easiest to start with a large brush to highlight the general selection, and then switch to a finer brush to fine-tune the selection.
4. Using the edge highlighter tool, drag over the fuzzy ends of the gorilla until you’ve completely outlined, but not filled, the gorilla. Draw the highlight so that it slightly overlaps both the foreground and background regions around the edge.
There’s no problem if the highlight overlaps the edge. The Extract command makes its selection by finding the difference in contrast between pixels. You don’t need to highlight areas where the object touches the image boundaries.
6. If necessary, select the zoom tool (), or press spacebar+Ctrl and click to zoom in on image. You can also use the hand tool () to reposition the image preview.
If you make a mistake and highlight more than desired, select the eraser tool () in the dialog box and drag over the highlight in the preview.
7. Select the fill tool in the Extract dialog box. Then, click inside the object to fill its interior. You must define the object’s interior before you can preview the extraction.
The default Fill colour (bright blue) contrasts well with the highlight colour (green). You can change either colour if you need more contrast with the image colours, using the Highlight and Fill menus in the Extract dialog box.
9. Click the Preview button to view the extraction.
At this stage the extraction is often ok, but rarely perfect. If the extraction looks really bad, then you can refine your selection. Choose Original from the Preview dropdown box at the bottom of the Extract dialog box and make your selection again using the highlighter and fill tools.
If you are reasonably happy with your selection, click OK to apply the extraction.
11. Often the selection can be improved dramatically by simply duplicating the layer.