Department of Creative Arts
St. Pius X High School

Ms. D. Gravelle

S2.T3 - Erasing Backgrounds

The Background Eraser Tool


Save the image below and open it in Photoshop

Background eraser The background eraser tool samples the background color as you paint and erases pixels in the same color range as you drag your brush across the image. The color range is determined by the tolerance setting in the background eraser options. Since this image had a background that was all over very similar in color, a low tolerance setting was used. Choose the discontiguous option because you want to remove the blue color everywhere it appears in the layer.

Because part of the foreground in this image is light colored, it may be easier to work with the background eraser by dropping in a contrasting color behind the layer so that you can see better. To do this, double click on the background to change it to a new layer, named "Jets".

Promoting the background to a layer.

Next, add a new layer, dragging it below the Jets layer and filling it with solid black. Later, this layer can be deleted or filled with another color.

A large brush works well for the background eraser.

When you click with the background eraser brush in your image, you need to be very careful that the crosshairs in the center of the brush land only in the background area. The crosshairs take a sample for the background color, so if the crosshairs touch the foreground, it will remove part of the foreground.

The first click removes a portion of the background

With my giant brush, make several individual clicks in the image rather than using a click and drag motion. When you make individual clicks, it's much easier to undo a mistake if you click too close to the foreground.

more of the background is removed.

Continue clicking until the area immediately surrounding the foreground is completely removed, then I go back and take out the surrounding background with a dragging motion.

continue clicking to remove all of the background

some specks of the background color remainYou can see in the enlarged view here that there are some specks from the background that were not completely removed. If you continue to carefully drag the brush around the image you can erase the majority of those specks.

most of the background is removed

To make sure all traces of the specks are completely removed, this is what you can do: Ctrl-click on the layer in the layers palette to load the layer as a selection...

selecting the layer

Then invert the selection (Selection > Invert) and press delete.

inverting the selection and deleting the remaining specks.

Here is the final image with the background removed and a new background dropped in to replace the black.

The final image with a new background.



Magnetic Lasso Tool

  This image is a perfect candidate for the magnetic lasso tool.

Save the Leaf and open it in Photoshop

What this image has going for it is a very distinct edge, which makes it a perfect candidate for the magnetic lasso tool. 


Magnetic Lasso Tool The magnetic lasso tool detects and snaps to the edge of an object as you to trace along its outline. The lasso width controls how close the edge you need to stay as you trace the image. Frequency controls how often points are laid down, and edge contrast Magnetic Lasso Tool Options helps you fine-tune the edge detection.



As you drag along the edge of an object, the tool drops fastening points to anchor the selection.

Using the magnetic lasso tool

Here's a few helpful shortcuts you should know about working with this tool: If you get too far away from the edge, you may get a point in the wrong place. You can back up and remove points by clicking the delete key as you use the magnetic lasso tool. You can also add points manually by clicking once where you want to place a point.

Using the magnetic lasso tool

When you get all the way around your object, your cursor will change when you hold it over the first point. Clicking once will close the selection and you'll see the selection marquee surrounding the image as shown below.

As you can see, the magnetic lasso failed to detect the object's edge around the stem area of the leaf. We can correct this fairly easily by zooming in  (Ctrl +) and adding nodes as we go.

 Press the keyboard space bar at any time to temporarily activate the hand tool for panning around the image. It should only takes a few minutes to touch up the edges of the selection this way.

Applying a gaussian blur in quick mask mode.  Apply a half-pixel gaussian blur to the mask just to soften the edge the slightest bit.

The selection of the leaf.

Next the selection is inverted (Selection > Invert) and the background is deleted by pressing delete on the keyboard. Make sure your image is on a layer before hitting delete. If the layer palette shows only one layer labeled background, you must promote it to a layer by double clicking on the background in the layers palette.

The selection is inverted and the background deleted.

Here's the final image with a new background. Additional refinements can be made along the edge of the leaf layer using the eraser tool.

The final image of the leaf with a newbackground.



The Eagle

Remove the Background and add in your own.