Erasing Backgrounds
Original ---- Enhanced

How I did it...

Using PSP8:   Erasing Backgrounds

Objective: To erase backgrounds in order to enhance photograph and then apply enhancement effects and different backgrounds.

Sometimes photographs may have backgrounds that you want to change or enhance differently than the main photo object. The techniques described here will work on any background though often those that are more complex in nature will benefit from these techniques.

1. Erasing Backgrounds

• If a background is a solid color, the easiest way is to use the magic wand and select that area and then use the delete key to get a transparent background. All photographs should have the background layer promoted to a layer.
• If the background is primarily a solid like background though may vary in hue and color somewhat, one could use the 'Background Eraser'. It is best when using this tool, to zoom the canvas so you can see more of the edge and possibly pixels of the object. This tool works by having the eraser pointer on the pixel (color) you want to remove. All such colors (hue) will then erase. Thus, moving the background eraser pointer to the pixels in the background at the edge of the object will ultimately remove most of the background. It is then best to test the area using the magic want to make sure all background is erased. Clean up can use the Eraser Tool.
• The disadvantage of the Background Eraser Tool is that if the edging pixels are similar in color as the object being preserved it is possible parts of that object with similar hue will be erased as well.

  Comment: Also, when using the eraser tools, or even the magic wand, experiment with various options and their values. With the magic wand, the 'Match Mode' of hue or color and tolerance set (value has to be determined) the selection will become slightly more accurate. With the eraser tools, sometimes setting Hardness to a lesser value helps preserve more of the edges.

2. Erasing Background and then Smoothing the Edges

• Another technique is to first use the magic wand to see if a fairly large part of the background is selected. Even if not, then use the selection tool and set it to ellipse. Zoom the image and use the Shift key to add to the selection and the Control Key to remove from the selection. In this fashion one can use the ellipse to get a selection much closer to the edge of the object. If part of the edge needs to be fixed use the Control Key to then remove that part of the selection. With the image zoomed one can ultimately get a fairly nice selection around the object and then can use the delete key to remove the background.

• When the background has been removed, there may be jagged edges on the object and there may be hues similar to the background that remain. There are a couple of techniques one can use at this point.
  • After using the magic wand to get a selection surrounding the object use Selections || Modify || Expand and set the value to a low value starting with a value of 1 and increasing by 1 until some of the edge area you want to remove is selected. Then just use the Delete Key.
  • Another technique is to use the Soften Tool and set Hardness and Opacity to lower values. Then with the canvas zoomed and a fairly small brush tip, just go around the edges with the Soften Tool and this technique may remove the colors and jags enough to satisfy.
• Now that you have cleaned up the edges more, they may still be more zagged than you want. Again, use the magic wand and if needed first use Selections || Modify || Expand with a value of 1 or 2. Then use Selections || Modify || Smooth. Check at least the Anti-alia box and experiment with checking the Preserve Corners box. Then start with a zero value for Corner Scale and then begin setting the values in Smoothing amount. Often values around 30 or so for Smoothing Amount are sufficient. The corner scale values will cause more rounding of the corners of your selection. Then use the Delete key and you should end up with a very clean, smooth edge on your object.

Comment: The picture illustrated is the Iris used in Activity #6, the background was erased using various techniques described ending up using the Selections Smoothing effect. Even though the background is black, the actual image is on a transparent background. Not how sharp and smooth the edges of the final image are and how even without further enhancements the photograph is more brilliant and sharp than the origina.

One could then add a layer below the object and create their own background.

-- Prof --