From 24625342597f76d8d033bcdecb7e9ab5cafc068e Mon Sep 17 00:00:00 2001
From: Nick Downing <nick@ndcode.org>
Date: Wed, 9 Feb 2022 12:50:05 +1100
Subject: [PATCH] More flexible block size, pitch and slippage parameters

---
 correlate.py | 51 +++++++++++++++++++++++++++------------------------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/correlate.py b/correlate.py
index d5f3aeb..0df159c 100755
--- a/correlate.py
+++ b/correlate.py
@@ -8,10 +8,18 @@ import scipy.ndimage
 import scipy.signal
 import sys
 
-# a BLOCKS x BLOCKS section is correlated with a (BLOCKS + 1) x (BLOCKS + 1)
-# the maximum allowable shift is BLOCK_SIZE with BLOCKS of surrounding context
-BLOCKS = 4
-BLOCK_SIZE = 64
+# size of block that will be matched
+# (correlate a block this size against a block with added slippage all around)
+XM = 128
+YM = 128
+
+# pitch between the block centres
+XP = 64
+YP = 64
+
+# allowable +/- slippage between pairs
+XS = 64
+YS = 64
 
 CORNER_CANDIDATES = 8
 
@@ -35,8 +43,8 @@ image1 = gamma.read_image(in_jpg1)
 assert image1.shape == shape
 
 ys, xs, cs = shape
-xb = (xs // BLOCK_SIZE - BLOCKS) // 2
-yb = (ys // BLOCK_SIZE - BLOCKS) // 2
+xb = (xs // 2 - XM - 2 * XS) // XP
+yb = (ys // 2 - YM - 2 * YS) // YP
 print('xb', xb, 'yb', yb)
 
 def bandpass(image):
@@ -51,19 +59,19 @@ def bandpass(image):
   )
 
 def correlate(image0_bp, image1_bp, xc, yc):
-  x0 = xc - BLOCKS * BLOCK_SIZE // 2
-  y0 = yc - BLOCKS * BLOCK_SIZE // 2
-  x1 = xc - (BLOCKS + 1) * BLOCK_SIZE // 2
-  y1 = yc - (BLOCKS + 1) * BLOCK_SIZE // 2
+  x0 = xc - XM // 2
+  y0 = yc - YM // 2
+  x1 = xc - XM // 2 - XS
+  y1 = yc - YM // 2 - YS
 
   block0 = image0_bp[
-    y0:y0 + BLOCK_SIZE * BLOCKS,
-    x0:x0 + BLOCK_SIZE * BLOCKS,
+    y0:y0 + YM,
+    x0:x0 + XM,
     :
   ]
   block1 = image1_bp[
-    y1:y1 + (BLOCKS + 1) * BLOCK_SIZE,
-    x1:x1 + (BLOCKS + 1) * BLOCK_SIZE,
+    y1:y1 + YM + YS * 2,
+    x1:x1 + XM + XS * 2,
     :
   ]
 
@@ -89,12 +97,12 @@ def correlate(image0_bp, image1_bp, xc, yc):
 
   y, x = numpy.unravel_index(numpy.argmax(corr), corr.shape)
   return (
-    (x - BLOCK_SIZE // 2, y - BLOCK_SIZE // 2)
+    (x - XS, y - YS)
   if (
     x >= CUTOFF1 and
-      x <= BLOCK_SIZE - CUTOFF1 and
+      x <= XS * 2 - CUTOFF1 and
       y >= CUTOFF1 and
-      y <= BLOCK_SIZE - CUTOFF1
+      y <= YS * 2 - CUTOFF1
   ) else
     None
   )
@@ -108,11 +116,6 @@ image1_bp = bandpass(image1)
 gamma.write_image('image1_bp.jpg', image1_bp + .5)
 
 print('find corner candidates')
-buckets = [[[], []], [[], []]]
-for i in range(yb - BLOCKS):
-  for j in range(xb - BLOCKS):
-    xc = j * BLOCK_SIZE + (BLOCKS + 1) * BLOCK_SIZE // 2
-
 p_all = []
 q_all = []
 corner_candidates = []
@@ -122,11 +125,11 @@ for i in range(2):
     offsets = []
     blocks = []
     for k in range(yb):
-      yc = k * BLOCK_SIZE + (BLOCKS + 1) * BLOCK_SIZE // 2
+      yc = YS + YM // 2 + k * YP
       if i:
         yc = ys - yc
       for l in range(xb):
-        xc = l * BLOCK_SIZE + (BLOCKS + 1) * BLOCK_SIZE // 2
+        xc = XS + XM // 2 + l * XP
         if j:
           xc = xs - xc
         offset = correlate(image0_bp, image1_bp, xc, yc)
-- 
2.34.1