Changeset 2186

Timestamp:

01/03/08 01:47:44 (5 years ago)

Author:

sam

Message:

• Add a colour gradient to the colour tests. They give very insightful information on the various distance choosers.

Location:

www/study

Files:

• grad5-1-1.png (added)
• grad5-1-2.png (added)
• grad5-2-1.png (added)
• grad5-2-2.png (added)
• grad5-2-3.png (added)
• grad5-2-4.png (added)
• gradient256.png (added)
• index.html (modified) (2 diffs)
• part5.html (modified) (3 diffs)
• study.py (modified) (6 diffs)

www/study/index.html

@@ -46 +46 @@
 <p> Meet Lenna. She will guide us through this document, because the
 seriousness of a scientific document in the area of computer graphics can
-be measured by the number of times Lenna appears in it. </p>
+be measured by the number of times Lenna appears in it. She truly is the
+<i>Mona Lisa</i> of image processing. </p>
 
 <p style="text-align: center;">
   <img src="lenna256.png" width="256" height="256"
        class="inline" alt="Lenna (256×256)" />
+  <img src="gradient256.png" width="64" height="256"
+       class="inline" alt="colour gradient (64×256)" />
   <img src="lenna256bw.png" width="256" height="256"
        class="inline" alt="Lenna (256×256BW)" />
   <img src="gradient256bw.png" width="32" height="256"
-       class="inline" alt="gradient" />
+       class="inline" alt="greyscale gradient (32×256)" />
 </p>
 
@@ -76 +79 @@
 
 <ul>
-  <li> <a href="part1.html">1. Colour quantisation</a> </li>
-  <li> <a href="part2.html">2. Halftoning patterns</a> </li>
-  <li> <a href="part3.html">3. Error diffusion</a> </li>
-  <li> <a href="part4.html">4. Greyscale dithering</a> </li>
-  <li> <a href="part5.html">5. Colour dithering</a> </li>
-  <li> <a href="part6.html">6. Photographic mosaics</a> </li>
+  <li> <a href="part1.html">1. Colour quantisation</a>
+    <ul>
+      <li> 1.1. Black and white thresholding </li>
+      <li> 1.2. Greyscale thresholding </li>
+      <li> 1.3. Dynamic thresholding </li>
+      <li> 1.4. Random dithering </li>
+    </ul>
+  </li>
+  <li> <a href="part2.html">2. Halftoning</a>
+    <ul>
+      <li> 2.1. Halftoning patterns </li>
+      <li> 2.2. Screen artifacts </li>
+      <li> 2.3. Ordered dithering </li>
+      <li> 2.4. Random ordered dithering </li>
+      <li> 2.5. Non-rectangular dither tiles </li>
+      <li> 2.6. Supercell dithering </li>
+      <li> 2.7. Void and cluster method </li>
+    </ul>
+  </li>
+  <li> <a href="part3.html">3. Error diffusion</a>
+    <ul>
+      <li> 3.1. Floyd-Steinberg error diffusion </li>
+      <li> 3.2. Floyd-Steinberg derivatives </li>
+      <li> 3.3. Changing image parsing direction </li>
+      <li> 3.4. Variable coefficients error diffusion </li>
+      <li> 3.5. Block error diffusion </li>
+      <li> 3.6. Sub-block error diffusion </li>
+    </ul>
+  </li>
+  <li> <a href="part4.html">4. Greyscale dithering</a>
+    <ul>
+      <li> 4.1. Introducing gamma </li>
+      <li> 4.2. Gamma correction </li>
+    </ul>
+  </li>
+  <li> <a href="part5.html">5. Colour dithering</a>
+    <ul>
+      <li> 5.1. Separate-space dithering </li>
+      <li> 5.2. Accounting for other dimensions </li>
+      <li> 5.3. TODO </li>
+    </ul>
+  </li>
+  <li> <a href="part6.html">6. Photographic mosaics</a>
+    <ul>
+      <li> 6.1. Image classification </li>
+    </ul>
+  </li>
 </ul>
 

www/study/part5.html

@@ -88 +88 @@
   <img src="out5-1-1.png" width="256" height="256"
        class="inline" alt="serpentine FS, 8 colours" />
+  <img src="grad5-1-1.png" width="64" height="256"
+       class="inline" alt="serpentine FS, 8 colours gradient" />
   <img src="out5-1-2.png" width="256" height="256"
        class="inline" alt="serpentine FS, 8 colours, gamma-corrected" />
+  <img src="grad5-1-2.png" width="64" height="256"
+       class="inline" alt="serpentine FS, 8 colours, gamma-corrected gradient" />
 </p>
 
@@ -144 +148 @@
   <img src="out5-2-1.png" width="256" height="256"
        class="inline" alt="Floyd-Steinberg, sum of absolute differences" />
+  <img src="grad5-2-1.png" width="64" height="256"
+       class="inline" alt="Floyd-Steinberg, sum of absolute differences gradient" />
   <img src="out5-2-2.png" width="256" height="256"
        class="inline" alt="Floyd-Steinberg, euclidian distance" />
+  <img src="grad5-2-2.png" width="64" height="256"
+       class="inline" alt="Floyd-Steinberg, euclidian distance gradient" />
 </p>
 
@@ -158 +166 @@
   <img src="out5-2-3.png" width="256" height="256"
        class="inline" alt="Floyd-Steinberg, 1×1 HSV cone" />
+  <img src="grad5-2-3.png" width="64" height="256"
+       class="inline" alt="Floyd-Steinberg, 1×1 HSV cone gradient" />
   <img src="out5-2-4.png" width="256" height="256"
        class="inline" alt="Floyd-Steinberg, 3×1 HSV cone" />
+  <img src="grad5-2-4.png" width="64" height="256"
+       class="inline" alt="Floyd-Steinberg, 3×1 HSV cone gradient" />
 </p>
 

www/study/study.py

@@ -241 +241 @@
 if chapter(0):
     grad256bw = Image((32, 256))
-    for x in range(32):
-        for y in range(256):
+    for y in range(256):
+        for x in range(32):
             grad256bw.setGray(x, 255 - y, y / 255.)
     grad256bw.save("gradient256bw.png")
 else:
     grad256bw = Image("gradient256bw.png")
+
+# Create a 64x256 colour gradient
+if chapter(0):
+    grad256 = Image((64, 256), True)
+    for y in range(255, -1, -1):
+        for x in range(64):
+            grad256.setRgb(x, y, x / 63., (255. - y) / 255, x / 63.)
+    grad256.save("gradient256.png")
+else:
+    grad256 = Image("gradient256.png")
 
 ##############################################################################
@@ -1253 +1263 @@
             for (i, j, e) in err:
                 img[y + j][x + i] += error * e / total
-    # 4. copy image, replacing gray with white
+    # 4. copy image, replacing grey with white
     for y in range(h):
         for x in range(w):
@@ -1911 +1921 @@
 
 if chapter(5):
+    test51x(grad256, ERROR_FSTEIN, test51y).save("grad5-1-1.png")
     test51x(lenna256, ERROR_FSTEIN, test51y).save("out5-1-1.png")
-    out512 = test51x(lenna256, ERROR_FSTEIN, test42x)
-    out512.save("out5-1-2.png")
+    test51x(grad256, ERROR_FSTEIN, test42x).save("grad5-1-2.png")
+    test51x(lenna256, ERROR_FSTEIN, test42x).save("out5-1-2.png")
 
 # Pattern 5.2.1: different colours give the same result
@@ -2075 +2086 @@
 
 if chapter(5):
+    test52x(grad256, ERROR_FSTEIN,
+            ANSI_PALETTE, distmax, True).save("grad5-2-1.png")
     test52x(lenna256, ERROR_FSTEIN,
             ANSI_PALETTE, distmax, True).save("out5-2-1.png")
+    test52x(grad256, ERROR_FSTEIN,
+            ANSI_PALETTE, disteuclidian, True).save("grad5-2-2.png")
     test52x(lenna256, ERROR_FSTEIN,
             ANSI_PALETTE, disteuclidian, True).save("out5-2-2.png")
@@ -2083 +2098 @@
     m = (float)(min(r, g, b))
     v = (float)(max(r, g, b))
-    if v == m:
+    if v == m or v == 0:
         return 0., 0., v
     s = (v - m) / v
@@ -2113 +2128 @@
 
 if chapter(5):
+    test52x(grad256, ERROR_FSTEIN,
+            ANSI_PALETTE, disthsv, True).save("grad5-2-3.png")
     test52x(lenna256, ERROR_FSTEIN,
             ANSI_PALETTE, disthsv, True).save("out5-2-3.png")
+    test52x(grad256, ERROR_FSTEIN,
+            ANSI_PALETTE, disthsv3, True).save("grad5-2-4.png")
     test52x(lenna256, ERROR_FSTEIN,
             ANSI_PALETTE, disthsv3, True).save("out5-2-4.png")