rds

Author: cgc

autostereogram/README.md

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+# Making a random-dot stereogram
+
+Surprisingly easy! Here's an ellipsoid:
+
+![](rds.png)
+
+Generated from this depthmap:
+![](depthmap.png)
+
+To write this relatively simple bit of code I referred to [wikipedia's description](https://en.wikipedia.org/wiki/Autostereogram#Random-dot) and [flothesof's python code](https://flothesof.github.io/making-stereograms-Python.html).

autostereogram/depthmap.png

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+import numpy as np
+from PIL import Image
+
+def make_sphere_depthmap(xlim, ylim, *, rad=1., size=200):
+    return np.array([
+        [
+            (rad**2 - x**2 - y**2)**(1./2) if x**2 + y**2 < rad**2 else 0
+            for x in np.linspace(xlim[0], xlim[1], size)
+        ]
+        for y in np.linspace(ylim[0], ylim[1], size)
+    ])
+
+def make_random_dot_stereogram(depthmap, pattern_size, *, shift_coef=0.3):
+    repeated = np.random.randint(0, 256, size=pattern_size).astype(np.uint8)
+    rds = np.zeros(depthmap.shape, dtype=np.uint8)
+    for x in range(rds.shape[1]):
+        for y in range(rds.shape[0]):
+            if x < repeated.shape[1]:
+                rds[y, x] = repeated[y % repeated.shape[0], x]
+            else:
+                shift = int(depthmap[y, x] * shift_coef * repeated.shape[1])
+                rds[y, x] = rds[y, x - repeated.shape[1] + shift]
+    return rds
+
+if __name__ == '__main__':
+    depthmap = make_sphere_depthmap((-2, 2), (-1.5, 1.5))
+    Image.fromarray((depthmap*256).astype(np.uint8)).save('depthmap.png')
+    Image.fromarray(make_random_dot_stereogram(depthmap, (50, 50))).save('rds.png')
+