A stereogram is a chaotic pattern image in which a secondary image is nestled. When you stare at a stereogram for an extended period of time, the secondary image appears to rise from the stereogram, allowing you to both make out its shape and perceive a 3D effect. You can create your own stereograms using Photoshop's various tools and features, then upload the image to your social networking account or use it in a project.
Press "Ctrl" and "N" to open the New Canvas window. Enter the dimensions you want for the stereogram. For example, enter "600" in "Height" and "800" in "Width" if you want the image to be 600 by 800 pixels. Press "Enter."
Click "Edit," then "Fill." Choose "Pattern." A window opens with a list of patterns. Choose a pattern you like and click "OK." A pattern with very small items that are placed close together, such as a stone or water pattern, is ideal.
Select the "Rectangular Marquee" tool. Draw a small rectangle in the middle of the stereogram. Press "Ctrl" and "C" to copy the pattern inside the selection. Click the "New Layer" button on the "Layers" window, then press "Ctrl" and "V" to paste the copied pattern. Press the right-arrow key on your keyboard 10 times to move the selection 10 pixels.
Click "File" and "Save" to save the image.
Some patterns produce better stereograms than others; experiment with multiple patterns to find one that works best for you.