Knowing how to remove one particular object from an image or photo is an essential skill for image manipulations. Each method; the Extract Filter, the Polygonal Lasso Tool, and the Quick Mask; has its own pros and cons. Learning all three techniques in Adobe Photoshop CS3 gives flexibility when you’re facing a deadline, or when precision is more important.
Open Photoshop, and then open the image to be used. Make sure the image is one that you own, have permission to use, or is in the public domain. It is always advisable to save a copy and then close the original to avoid accidentally altering the original.
Perhaps the easiest way to extract an object from the background is to use the Extract Filter. This method can also be the least precise. Click on Filter, and then click on Extract…. The Extract menu will open, with a number of customizable options to the right. Outline the object to extract, holding the Ctrl key to snap your movements to the edges. Change the size of the brush for finer details. If you accidentally paint over the object, click on the Eraser Tool inside the menu to remove the line you painted. When you have finished the outline, click on the Fill Tool to fill in the object. Click OK, and your extracted object will appear on a transparent background.
Another technique uses the Polygonal Lasso Tool to remove the unwanted parts of the image. Click on the Lasso Tool and hold it to show the other tool options, and then click on the Polygonal option. You can choose the regular Lasso Tool, but the Polygonal allows for more precision. Click along the edges of the object (or, if using the regular Lasso, carefully go around the object) until it is completely outlined, zooming in if necessary to be more precise. Now click on Select, and then click on Inverse. With the unwanted background selected, hit the Delete key. The background is removed, leaving only the object.
The third method, using Quick Mask, will give the smoothest edging on the object. It also uses the Polygonal or regular Lasso Tool, but you do not have to be as careful with the selection. Create a basic outline around the object, and then hit Q. This puts you in Quick Mask Mode, and makes the unwanted background red. Click on the Brush Tool, make sure it is a basic round shape, and then set the color to black or white. White will add to the selection, and black will subtract from the selection. To avoid confusion, remember that the red area is deselected. Use the white only if the object is painted over to remove the red. Zoom in if necessary for details. Once you have finished, hit Q again to exit the Quick Mask Mode. The object is selected, and can be cut and pasted into another image.
Any one of these techniques will enable you to extract a certain element in an image or photo from the background. Decide which works best for you, or learn them all for more flexibility in your work or hobby.