Different Ways to Remove a Background
This tutorial will cover how to use the Magic Wand, Instant Alpha Eraser, Blending Modes, and Filters to remove the background of an image. You can also check out this video tutorial created by MacMost.
The original image in this example is asparagus with a green background. The goal is to remove the green background.
The Magic Wand Method
Select the magic wand in the tools palette. Notice in the inspector palette there is a field labeled Wand Tolerance. This number adjusts the range of colors that the magic wand will select. Using the magic wand, click and drag on the background to select it. You will see a circle near your cursor increase or decrease in size in response to the change in tolerance. How far you drag in or out will determine the amount selected and you can see in real time how your selection grows or shrinks. You can tell the background has been selected by all of the little ants marching around it.
Now hit the Delete key and deselect by going to Select ▸ Clear Selection (⌘D). You can see the original background has been removed completely. The checkered pattern indicates transparency.
The Instant Alpha Erase Tool Method
Click on the instant alpha tool in the tools palette. Instant alpha is an erasing tool that has similar qualities to the magic wand selection tool. Click on the color you want erased and simultaneously click and drag outwards to increase the erasing tolerance, or inwards to decrease. The results will be seen in real time as you drag inwards and outwards.
As you can see in the above image, the green background is removed leaving transparency. This is because there is no layer below the asparagus to show through the erased green area.
The Transparentomatic Filter Method
Go to Filter ▸ Color Adjustment ▸ Transparentomatic. Click once on the color well to the right of where it says 'Remove'. This will bring up the colors palette. Click on the magnifying glass to the left of the colors display in the colors palette. Using the magnifying glass click on the background in the image. That color will be removed. Play around with the tolerance level of the filter until things look right. Multiple transparentomatic filters can be added to remove multiple background colors.
The Blending Modes Method
Select your background using the magic wand tool. Go to Layer ▸ New Layer with Selection. Deselect (⌘D). Now change the blending mode of the layer to Destination Out. This will create a transparent background that is easily hidden or visible by turning the visibility of the new layer on and off.