Stereogram Generator
Create your own hidden 3D pictures, the kind made famous by Magic Eye posters. Type a word, pick a shape or upload a depth map, choose random dots, a colorful texture or your own pattern tile, and download a high-resolution PNG. The image updates as you type and is generated entirely on your device.
Last updated:
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How to see the hidden image
- Make the picture large and sit about an arm's length away.
- Relax your eyes and look through the screen, as if at a wall far behind it.
- Watch the two guide dots: when they turn into three, hold that gaze.
- Slowly let the image come into focus; the 3D shape will appear. Try Cross-eyed mode if you prefer crossing your eyes.
How to use the Stereogram Generator
- Choose what to hide: type text, pick a shape or upload a depth map where white is closest to you.
- Pick a pattern: a colorful texture is easiest to view; random dots give the classic look; or upload your own tile image.
- Adjust depth and pattern width. Smaller pattern widths are easier for beginners; more depth makes the object pop out further.
- View it: relax your eyes and look through the screen as if at something far behind it, until the two guide dots become three.
- Download the PNG to share or print. Use a larger size for posters.
How a stereogram hides a 3D shape
Your eyes are about 6 to 7 cm apart, so each sees a scene from a slightly different angle, and your brain turns that difference (disparity) into depth. A stereogram exploits this. The picture is made of a pattern that repeats roughly every P pixels. When you look "through" the image, your left eye lands on one repeat and your right eye on the next, and the brain fuses them. Wherever the repeat distance is slightly shorter, the fused point appears closer to you; where it is longer, it appears further away. The hidden object is nothing more than a map of tiny changes in repeat distance.
This generator computes, for every pixel, the separation s = round((1 − μz) · E / (2 − μz)), where z is the depth from 0 (background) to 1 (nearest), μ is the Depth setting and E is twice the pattern width. The background (z = 0) repeats exactly every P pixels and the nearest point repeats every 2P(1 − μ)/(2 − μ) pixels. Pixels that must look the same are linked into chains, points that one eye could not see past a nearer surface are skipped (hidden-surface removal), and the pattern is copied along each chain from right to left.
Settings guide
| Setting | What it changes | Good starting point |
|---|---|---|
| Depth | How far the object floats in front of the background (μ) | 25 to 35 %; above 45 % can be hard to fuse |
| Pattern width | Repeat distance of the background; your eyes must diverge by this much | About 1/8 of the image width, roughly 2.5 to 3 cm on screen |
| Edge smoothing | Blurs the depth map to soften jagged outlines | 1 to 3 px for text and shapes, 0 for detailed depth maps |
| Pattern | What the repeating texture looks like | Colorful texture for beginners, random dots for the classic look |
| Viewing | Wall-eyed (look past) or cross-eyed (look in front) | Wall-eyed, the standard for posters and books |
Tips for great hidden pictures
- Keep it bold. Short words in heavy letters, simple silhouettes and smooth gradients are far easier to see than thin lines or small detail.
- Size for the screen or print. For a printed poster, choose 2400 × 1500 and keep the pattern repeat about 2.5 cm wide on paper so it matches the gap between your eyes when viewed from a normal distance.
- Make your own depth map in any paint program: paint the background black, near parts white and use soft gradients for rounded surfaces. 3D apps can also export a Z-depth pass, which works perfectly here.
- Fusing trouble? Turn on guide dots, lower the Depth and pattern width, and try the colorful texture pattern, which gives your eyes more to lock on to.
- Check your work with Reveal depth map before downloading, so you know exactly what the viewer should find.
Frequently asked questions
What is a stereogram?
An autostereogram is a single flat image that hides a 3D shape. A pattern is repeated horizontally, and tiny changes in how far apart the repeats are encode depth. When your two eyes look at neighbouring repeats instead of the same point, your brain fuses them and sees the hidden object floating in front of or behind the background. Magic Eye is the best-known brand of this kind of picture.
How do I see the hidden 3D image?
Bring the screen close to your face so it looks blurry, relax your eyes as if looking through the screen at something far away, then slowly move back. Keep your gaze relaxed and the shape will appear. The guide dots help: when you see three dots instead of two, your eyes are at the right angle. It can take a minute the first time and becomes easy with practice.
What is the difference between wall-eyed and cross-eyed viewing?
Wall-eyed (parallel) viewing means looking past the image; it is the standard for stereogram posters. Cross-eyed viewing means focusing in front of the image by slightly crossing your eyes. The same picture shows the opposite depth in each mode, so this tool inverts the depth map when you pick cross-eyed, making the object pop out correctly for that method.
How does the stereogram algorithm work?
For every row, each point of the depth map tells how far apart its left-eye and right-eye image must be: separation = round((1 - μz) × E / (2 - μz)), where z is depth from 0 (far) to 1 (near), μ is the depth factor and E is twice the pattern width. Pixels that must match are linked, hidden-surface checks skip points one eye cannot see, and the pattern is then copied along each chain of links. This method was published by Thimbleby, Inglis and Witten in 1994.
What makes a good depth map?
A grayscale image where white is closest, black is the background and smooth gradients describe curved surfaces. Bold, simple shapes and thick letters work best. Very fine detail and thin lines are hard to see because each pattern repeat is only around 100 pixels wide. A little edge smoothing reduces jagged outlines.
Which pattern should I choose?
Colorful texture patterns are the easiest to fuse because they contain recognisable detail. Random dots give the classic SIRDS look and hide the shape perfectly but take more effort to view. A custom tile works best if it is busy and evenly detailed, such as foliage, pebbles or confetti, without large flat areas.
Are stereograms safe to look at?
For most people viewing stereograms is just a relaxing focus exercise. If you feel eye strain or a headache, take a break. Some people with reduced vision in one eye or limited depth perception cannot see the effect, which is normal.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.