Tutorial: Making Selections

Subject:

Selecting portions of an image

Level:

Beginning

Objectives:

Learning how to use the different tools for selecting objects/regions of an image for modifying and editing.

Resources:

cookie.jpg, Photoshop Elements 2.0

Overview

If you wish to edit or modify a particular area of an image you must first select it--in the same manner that you might select a sentence or phrase in a text document for separate formatting. Photoshop Elements offers a variety of tools and techniques for selecting objects or regions of an image. In this activity, you will be introduced to these and gain some experience using them. It is important to note that not only do these methods vary, but so do their results. In other words, some are "quick and dirty" and others are more sophisticated or sensitive. In use, your choice should depend upon what you plan to do with the selected area.

Figure 1. Using the marquee tool to select the area around the cookie.

1. Marquee Tool.

The marquee tool allows you to select a rectangular area of an image. Open the cookie.jpg image. (You may download it from the link above.) Select (i.e., click on) the marquee tool. When you move the mouse pointer into the image, the pointer will appear as a crosshair. Starting at the upper left-hand corner of the cookie, click and drag diagonally to form a box like that pictured above in Figure 1. When the box surrounds the cookie, you may release. The area will be highlighted by the "crawly ants" display--dotted lines that appear to be moving. Select the move tool (next to the selection tools). Move the pointer into the selected area; click and drag it downward about an inch. What happens after you release?

  As you can see, the entire area is affected. Both the cookie and its surrounding area are moved. The "hole" that you see is actually the background color used to fill in the vacated space. Anytime that you use marquee tool for selection, the affected area will always be the contents of the rectangle.

  Choose Save As from the File menu and name this version cookie1.psd. (In other words, save as a Photoshop file.)


Figure 2. Using the oval tool to select the surrounding area of the cookie.

2. The Oval Tool.

The oval tool works very much like the marquee tool, except that it selects an elliptical or circular area in the image. (Open the original version of cookie.jpg image, if it is not already open.) Select the oval tool. While holding down the Shift key, start in the upper left-hand corner--well outside the area of the cookie--click and drag diagonally as before. (Holding down the Shift key constrains the shape to a circle; otherwise, it would be an oval or ellipse.) When the circle surrounds the cookie, you may release the mouse button. When you release, a circular area around the cookie should be selected as in the image above in Figure 2.

  This area can then be edited or modified as before. Try moving it. Again, save this version using Save As from the File menu. Call it cookie2.psd.

Tip:

When using any of these and other selection tools, you may control how sharply defined the selected area will be. While the selection tool is highlighted, the toolbar will display the "Feather" box. Note that the feather control is currently set to a radius of zero pixels. Change the value in the box to read "3." This means that the selected area will be blended with the background color for an area of 3 pixels in width. Now select an elliptical area around the cookie.

  While the selection is active, we will copy this to a new image. Specifically, choose Copy from the Edit menu. Next choose New from the File menu. The dialog box asks you to confirm the size and type of image. Since it is now based on the size of the selection currently on the Clipboard, it should be fine. Click OK to close the dialog box. When the new "empty" image appears, select Paste from the Edit menu. The cookie will appear with a blended or feathered border. A nice effect that is easy to do.

  Close the new picture. You won't need to save it.


Figure 3. Using the lasso tool to make a freeform selection.

3. The Lasso Tool.

The lasso tool is employed to make freeform selections usually around an object with irregular boundaries. (Open the original version of the cookie.jpg image, if it is not already open.) Select the lasso tool. Outside the area of the cookie, click and drag around it. When you release, a freeform area around the cookie should be selected, as in the image in Figure 3.

  This area can then be edited or modified as before. Try moving it with the move tool as before. What happens this time? Once again, as you can see, the cookie and its surround are affected.

  Use Save As from the File menu to save this version as cookie3.psd


Figure 4. Using the polygon lasso tool to surround the cookie area.

4. The Polygon Lasso Tool.

The effect of the lasso tool can be improved somewhat. (Open the original version of the cookie.jpg image, if it is not already open.) Select the polygon lasso tool again.Click around the edges of the cookie to make a path of short straight lines. Each click establishes a point and the next point creates the line segment. When you get all the way around to the original point, an "O" will appear when the mouse is over that point. This signifies a closed path. Click again to close the path and the selection. The result should resemble that in Figure 4.

  This area can then be edited or modified as before. Try moving it as before. Use Save As from the File menu to save this version as cookie4.psd


Figure 5. Using the magic wand to segment a region of an image.

5. The Magic Wand.

The magic wand can be used to create segmentations of an image. A segment is a connected region of an image in which all of the pixels share some common or similar attribute--usually color or shade. The magic wand samples an area of an image and copies its color. It then collects all neighboring pixels that have the same or similar color.

  (Open the original version of the cookie.jpg image, if it is not already open.) Select the magic wand tool. When you move the pointer into the image, it will appear as a wand. The selector is actually the tip of the wand (marked by an "X"). Move it over the image to an area that is a good representative of the cookie's color. Click it and a selection will grow to segment the region. The size and shape of the segment will depend upon the area that you first selected. You may increase this segmentation by holding down the Shift key and clicking the magic wand in unselected areas of the cookie. Try this to expand the segment. (Another approach is to use the Grow command from the Select menu. Try this too.) Try to capture as much of the cookie as you can without expanding the segment to the rest of the image. Compare your results with those in Figure 5.

  The selected area can then be edited or modified as before. Try moving it with the move tool. What happens this time? As you can see, the cookie moves, but any of the areas inside it not selected remain in the same position.

  Use Save As from the File menu to save this version of the image as cookie5.

Tip:

You can surround the cookie using the magic wand and a few other tricks too. (Open the original version of the cookie.jpg image, if it is not already open.) Select the magic wand tool again. This time, however, click the background color outside the cookie. Since it is fairly uniform, the resulting segment should be the entire background--minus the cookie and its crumbs. Next, choose Invert from the Select menu. The segment will swap to the regions of the cookie and its crumbs. Almost done. Naturally, we want to select the cookie and not the crumbs.

  You can subtract from any selection by holding down the ALT key and selecting the areas that you wish to eliminate from it. While holding down the ALT key, use the lasso tool to drag around the cookie crumbs. (You can do this in several steps.) Eventually, you should be able to reduce the segment to just that surrounding the cookie.


Figure 6. Using the magnetic lasso to surround the object with paths and points automatically

6. The Magnetic Lasso Tool

The Magnetic Lasso Tool is especially useful for capturing irregular figures like the cookie. (Open the original version of the cookie.jpg image, if it is not already open.) Select the magnetic lasso tool. The magnetic lasso creates a freeform path around the object much like the polygon lasso tool; the difference, though, is that the magnetic lasso tool makes the path automatically--without the need of clicking points all the way around the object. The lasso looks for border between contrasting colors. Thus, the path should fit snugly around the edge of the cookie as seen in Figure 6.

  You start the magnetic lasso by choosing a spot to create the fastening point. Click near the edge of the cookie. Now move the mouse (with or without pressing the mouse button). As you move or drag, the line will snap to the edge of the shape. Temporary points will appear automatically as you drag around the cookie. Click the starting point to close the path and complete the selection. Try moving this selection as before.

  Use Save As in the File menu to save this version as cookie6.psd.


7. Saving a Selection.

Sometimes it is convenient to save a selection for use later. PE allows you to make a selection, save it (with the image file), and reactivate the selection at some later time. We will walk through the procedure.

  (Open the original cookie.jpg image, if it is not already opened.) With the magnetic lasso tool, make another selection of the cookie. While the selection is active, choose Save Selection from the Select menu. A dialog box will ask you what to name the selection. Let's call it, "cookie." Enter the word and press OK. Now we will deselect (that is, deactivate) the current selection. Choose Deselect from the Select menu. The crawly ants should disappear.

  We can restore the selection easily. Choose Load Selection from the Select menu. Select the cookie selection. It will appear once more.

  Use Save As from the File menu to save this version as cookie7.psd

[You have completed this lesson.]

©Abernethy and Allen, 2003
Furman University
Last Modified: 2/03.