Replacing faces on pictures can serve several purposes, but no matter the reason, the process is still the same--cutting one image and pasting another in its place. The tricky part is making the replacement look realistic. Faces in pictures are complicated because they usually are different sizes and feature different shades of lighting, angles, positions and other factors. The more similar the original pictures, the easier the manipulation and more realistic the replacement will look. There are plenty of graphics editing programs, either pricey or free, that are able to manipulate pictures. The basic process is the same, but each program has its own set-up.
Choose two pictures with faces that are about the same size, if possible, because some degradation might appear if one needs to be enlarged. Also, keep the angles of the faces in mind. For instance, it will not look good if one head is turned sideways and the other is a front shot. Try to get two side shots or two front shots, so as little manipulation as possible is required. The less that needs to be edited, the less the degradation and the more realistic the final picture. Also, the pictures need to be in a JPEG, BMP or PNG format or they can't be edited properly with layers. A GIF format will not work and will need to be converted.
Load a graphics program, such as Paint Shop Pro. Go to "View." Click on "Toolbars." Check the box for "Tools Options Palette" if "Tools Options" is not already open.
Click on "File, and click "Open." Locate your pictures, and click "Open."
Maximise the picture on which you want to have the face replaced and enlarge it with the Zoom tool (the magnifier icon) until it fills up a large part of the screen.
Open the "Tool Options" and set the "Selection Type" to "Point-to-Point" and "Feather to 0."
Outline the face on the picture using the Freehand selection tool (lasso icon) to trace around the head. Try to get the line as close to the head as possible. If necessary, outline the head a pixel outside of it to make sure you get all the head.
Click on the "Arrow" icon, right-click over the outlined image, and click "Cut." The outlined area will change to white or whatever the background colour is. Right-click on an empty part of the workspace, and click "Paste as New Image" to open the face as a new image.
Repeat Steps 4 through 6 on the picture you want to place on the other picture. When it is time to "cut" the outlined image, click "Copy." Right-click on an empty part of the workspace and choose "Paste as New Image" to open the face image.
Highlight the title bar of the cut image and look at the bottom-right status bar to find the image size. Highlight the title bar of the copied image. Resize it by going up to "Image" then clicking "Resize." Set the pixel size to the largest dimension of the cut picture and click "OK."
Click "Colors," then "Adjust." Choose from a slew of tools to edit the picture. Most of the time, you need to adjust only the "Brightness/Contrast."
Go to "File" and click "New" to open a new blank white image. Set the image dimensions to larger than the size you found a moment ago. Copy and paste the replacement face image onto the blank image as a new layer.
Go to "Layers," and choose "Merge," then "Merge All."
Select the replacement face's background colour with the Magic Wand tool. Click "Selection," then click "Invert," which will invert the selection and trace the face instead.
Right-click on the outlined face with the "Arrow" tool, and paste it as a new layer onto the picture that is cut out. Use the cursor to position the head directly over the spot where the head was cut out. Try to line the neck up where it belongs as best you can. Slight overlapping of a pixel or two is fine. When it is in position, merge the layers as before.
Use the "Clone" tool if there is empty space around the face because it's smaller than the cutout. Click on the "Clone" tool icon (double brushes). In the "Tool Options" menu, set "Shape" to round, "Size" to 1, "Hardness" to 0, "Opacity" and "Density" both to 100, and a step of 25. On the second tab, set "Clone" mode to "Aligned. "
Right-click the cursor on a spot on the background immediately outside the blank cut out space, then left-click on the blank space directly opposite the area you just right-clicked. The colour of the background will be "cloned" and blended into the blank area, filling it in. Depending on the complexity of the background colours and size of the blank space, it might be necessary to clone more than one colour as you go around the head.
If the toolbar is in your way, minimise it by clicking the toggle button on it next to the "X" close button. This allows the toolbar to remain open while in use and minimised when you click anywhere outside the toolbar. If the replacement face isn't large enough to cover the cutout, it can be enlarged to cover it. That might cause distortion or create a head that is out of proportion with the body, which is fine if you are going for a caricature effect.