Changeset 1937

Timestamp:

11/11/07 22:16:15 (6 years ago)

Author:

sam

Message:

• Burkes dithering.

Location:

www/study

Files:

• fig3-2-4.png (added)
• fig3-2-4.svg (added)
• grad3-2-4.png (added)
• index.html (modified) (2 diffs)
• out3-2-4.png (added)
• study.py (modified) (2 diffs)

www/study/index.html

@@ -337 +337 @@
 </p>
 
-<p> Finally, <b>Stucki dithering</b> is a slight variation of
-Jarvis-Judice-Ninke dithering: </p>
+<p> <b>Stucki dithering</b> is a slight variation of Jarvis-Judice-Ninke
+dithering: </p>
 
 <p style="text-align: center;">
@@ -347 +347 @@
   <img src="grad3-2-3.png" width="32" height="256"
        class="inline" alt="Stucki error diffusion gradient" />
+</p>
+
+<p> <b>Burkes dithering</b> is yet another variation: </p>
+
+<p style="text-align: center;">
+  <img src="fig3-2-4.png" width="200" height="120"
+       style="margin-right: 30px;" alt="Burkes" />
+  <img src="out3-2-4.png" width="256" height="256"
+       class="inline" alt="Burkes error diffusion" />
+  <img src="grad3-2-4.png" width="32" height="256"
+       class="inline" alt="Burkes error diffusion gradient" />
 </p>
 

www/study/study.py

@@ -346 +346 @@
 
 # Output 3-2-3: Stucki
-# TODO: merge with Jarvis, Judice and Ninke
+# TODO: merge with Jarvis-Judice-Ninke
 def test323(src, name):
     (w, h) = src.size()
@@ -379 +379 @@
 test323(lenna256bw, "out3-2-3.png")
 test323(gradient256bw, "grad3-2-3.png")
+
+# Output 3-2-4: Burkes
+# TODO: merge with Jarvis-Judice-Ninke and Stucki
+def test324(src, name):
+    (w, h) = src.size()
+    dest = Image((w, h))
+    ep = [0.] * (w + 4)
+    for y in range(h):
+        ey = [0.] * (w + 4)
+        ex = 0
+        ex2 = 0
+        for x in range(w):
+            c = src.getGray(x, y) + ex + ep[x + 2]
+            d = c > 0.5
+            dest.setGray(x, y, d)
+            error = c - d
+            ex = ex2 + error * 8. / 32.
+            ex2 = error * 4. / 32.
+            ey[x] += error * 2. / 32.
+            ey[x + 1] += error * 4. / 32.
+            ey[x + 2] += error * 8. / 32.
+            ey[x + 3] += error * 4. / 32.
+            ey[x + 4] += error * 2. / 32.
+        ep = ey
+    dest.writePng(name)
+
+test324(lenna256bw, "out3-2-4.png")
+test324(gradient256bw, "grad3-2-4.png")
 
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