164. Replace a Background with Something Else
Before You Begin
111 Select Tool Options
97 Erase Part of a Layer
162 Remove Unwanted Objects from an Image
165 Fix a Bland-Looking Sky
One of the simplest special-effects tricks you can pull off is to remove the background from around a subject and replace it with something else. For example, are you the only one who didn't make it to a recent family reunion? There's no reason you have to remember that fact foreverjust use the Background Eraser to remove the background from a recent photo of yourself, and then replace the background with the reunion photo. After a few minutes' work, you'll be partying with your cousins. Of course, there are legitimate reasons for needing to replace an image background as wellfor example, if you have a photo of someone in a black suit on a dark background, you won't be able to do much using the Editor's contrast controls to separate them visually. Better to select the man and place him on a lighter background that provides more contrast.
The secret to using the Background Eraser tool is to slow down and watch where you're going. Its job is to erase colors that are similar to those at the center of the pointer. What gets erased are pixels with similar colors within the circular area of the brush tip. To control which pixels are similar enough to warrant erasure, adjust the tool's Tolerance and Limits options. When you set Limits to Contiguous, the Background Eraser tool samples the pixel under the hotspot, located at the center of the brush tip, and erases only those similarly colored pixels under the brush that touch the hotspot, or some other similarly colored pixel. Contiguous is typically your best bet, although Discontiguous erases any and all similarly colored pixels under the brush tip, regardless of their position. By default, the Limits value is set to Contiguous, but this setting might make it difficult to erase the background if it peeks through your subject (as the sky does through tree branches). Use Discontiguous in such a case.
Select Background Eraser Tool
Open an image in the Editor in Standard Edit mode and save it in Photoshop (*.psd) format. On the Toolbox, click the Background Eraser tool.
On the Options bar, select the brush tip you want to use. Click the arrow next to the brush tip to adjust the Diameter (size), Hardness, and other options you want. See 111 About Tool Options for descriptions of these options.
If you want to erase from this layer by sampling visible pixels from all layers, use the Magic Eraser tool and enable its Use All Layers option. You can also partially erase pixels with the Magic Eraser tool (by adjusting the Opacity setting). See 97 Erase Part of a Layer.
To prevent yourself from accidentally erasing something you don't want to, make a selection firstthe Background Eraser erases only the pixels within the selection. For example, to erase the sky around a girl's face who also happens to be wearing a blue hat, draw the selection boundary omitting the hat so that it isn't mistaken for the background and isn't erased as you work at removing the background from around her face.
Drag to Erase
In the Layers palette, change to the layer you want to eraseif you erase pixels from the Background layer, the Editor will automatically convert that layer to a regular layer after the end of your first stroke because the Background layer can't contain transparent pixels (which the Background Eraser creates).
Click and drag with the Background Eraser tool. Pixels that are a relative match for the pixel under the center of the brush tip (the hotspot, which is marked by the crosshair) are erased from the layer (made transparent). To keep things straight, you might want to rename this layer Subject.
Insert New Background
After erasing the background from around a subject, replace the background with something else. Open the image you want to use as the background, and if necessary, select the layer you want to use from the Layers palette. Choose Select, All to select all the pixels in your background image that reside on that particular layer, and choose Edit, Copy to copy them to the Clipboard.
Paste the new background into the image you're editing by activating its window again, and then choosing Edit, Paste. This action creates a new layer with the contents from the Clipboard (the new background you want to use). Rename the layer Fake Background.
In the Layers palette, drag the Fake Background layer below the Subject layer so that the new background appears in the holes the Background Eraser tool created. Resize and reposition the Fake Background layer if needed. See 99 Move, Resize, Skew, or Distort a Layer.
If you want to place the original image on a Web page background or your Windows desktop, just skip step 4 and leave the background around the subject transparent. To retain the transparent pixels when you resave the completed PSD file, use GIF, PNG, or JPEG 2000 format.
View the Result
After you're satisfied with the result, make any other changes you want, then save the PSD file. Resave the result in JPEG or TIFF format, leaving your PSD image with its layers intact so that you can return at a later time and make different adjustments if you want. For example, you might want to try out some different backgrounds and have some fun!
To quickly copy a layer from one image to another, select that layer in the Layers palette and drag and drop it into the other image window. If the Layers palette isn't visible, you can drag and drop using the Move tool.
Last year, my sister Pat let me borrow an old picture of her pushing a walker around our driveway; when I looked at it, I couldn't help but imagine her racing someplace sportier. I just happened to have a photograph of the Indianapolis 500 track (taken while my husband was driving around on it in his sports car), so I merged the two to create a cute photo. This year, I did it one better by adding my daughter on roller skates. Now they can race each other to the checkered flag.
Because the walker image was in grayscale, I changed the image mode in my daughter's photograph to grayscale before copying the image of my daughters into the master PSD file. I then resized and positioned my daughter just behind my sister on her walker.