1 files changed, 48 insertions, 0 deletions
diff --git a/study/create_matrix.py b/study/create_matrix.py
new file mode 100755
index 0000000..1599a12
--- /dev/null
+++ b/study/create_matrix.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+
+import sys
+
+def usage():
+    print("usage: Kr Kg Kb full|limited")
+    print("examples:")
+    print("  create_matrix.py 0.2126 0.7152 0.0722 full")
+    print("  create_matrix.py 0.2126 0.7152 0.0722 limited")
+    exit(1)
+
+def a(v):
+    if v >= 0:
+        return " %f" % v
+    else:
+        return "%f" % v
+
+def main(argv):
+    if len(argv) != 5:
+        usage()
+
+    Kr = float(sys.argv[1])
+    Kg = float(sys.argv[2])
+    Kb = float(sys.argv[3])
+    color_range = sys.argv[4]
+    luma_offset = 0.0
+    transform_range = 1.0
+
+    if color_range == "full":
+        pass
+    elif color_range == "limited":
+        transform_range = (235.0 - 16.0) / 255.0
+        luma_offset = 16.0 / 255.0
+
+    matrix = [
+        [Kr,                        Kg,                        Kb],
+        [-0.5 * (Kr / (1.0 - Kb)), -0.5 * (Kg / (1.0 - Kb)),  0.5],
+        [0.5,                      -0.5 * (Kg / (1.0 - Kr)), -0.5 * (Kb / (1.0 -Kr))],
+        [0.0,                       0.5,                      0.5]
+    ]
+
+    # Transform from row major to column major for glsl
+    print("const mat4 RGBtoYUV = mat4(%f, %s, %s, %f,"  % (matrix[0][0] * transform_range, a(matrix[1][0] * transform_range), a(matrix[2][0] * transform_range), 0.0))
+    print("                           %f, %s, %s, %f,"  % (matrix[0][1] * transform_range, a(matrix[1][1] * transform_range), a(matrix[2][1] * transform_range), 0.0))
+    print("                           %f, %s, %s, %f,"  % (matrix[0][2] * transform_range, a(matrix[1][2] * transform_range), a(matrix[2][2] * transform_range), 0.0))
+    print("                           %f, %s, %s, %f);" % (matrix[3][0] + luma_offset,     a(matrix[3][1]),                   a(matrix[3][2]),                   1.0))
+
+main(sys.argv)