Add Matrix4x3 and tristimulus class to color utiliies.

ui/gfx/color_utils.cc

Index: ui/gfx/color_utils.cc
diff --git a/ui/gfx/color_utils.cc b/ui/gfx/color_utils.cc
index d64a8b3636059cf5c79c714ff39e0983d2ddba9d..d7149bae22aec455deb45efc5c58df45107957b6 100644
--- a/ui/gfx/color_utils.cc
+++ b/ui/gfx/color_utils.cc
@@ -23,7 +23,6 @@
 
 namespace color_utils {
 
-
 // Helper functions -----------------------------------------------------------
 
 namespace {
@@ -64,6 +63,89 @@ SkColor LightnessInvertColor(SkColor color) {
 
 // ----------------------------------------------------------------------------
 
+Matrix4x3::Matrix4x3() {
+  for (int row = 0; row < 3; row++) {
+    for (int col = 0; col < 4; col++) {
+      rows[row][col] = row == col ? 1.0f : 0.0f;
+    }
+  }
+}
+
+float Matrix4x3::lookup(int row, int col) const {
+  if (row == 3)
+    return col == 3 ? 1.0f : 0.0;
+  return rows[row][col];
+}
+
+Matrix4x3 Matrix4x3::operator*(const Matrix4x3& other) const {
+  Matrix4x3 ret;
+  for (int col = 0; col < 4; col++) {
+    for (int row = 0; row < 3; row++) {
+      float sum = 0.0;
+      for (int i = 0; i < 4; i++) {
+        sum += lookup(i, col) * other.lookup(row, i);
+      }
+      ret.rows[row][col] = sum;
+    }
+  }
+  return ret;
+}
+
+TriStim Matrix4x3::operator*(const TriStim& color) const {
+  TriStim ret;
+  ret.values[0] = rows[0][0] * color.values[0] + rows[0][1] * color.values[1] +
+                  rows[0][2] * color.values[2] + rows[0][3];
+  ret.values[1] = rows[1][0] * color.values[0] + rows[1][1] * color.values[1] +
+                  rows[1][2] * color.values[2] + rows[1][3];
+  ret.values[2] = rows[2][0] * color.values[0] + rows[2][1] * color.values[1] +
+                  rows[2][2] * color.values[2] + rows[2][3];
+  return ret;
+}
+
+Matrix4x3 Matrix4x3::Invert() const {
+  Matrix4x3 ret, m(*this);
+  for (int col = 0; col < 4; col++) {
+    if (m.rows[col][col] != 1.0) {
+      int best = col;
+      for (int row = col + 1; row < 3; row++) {
+        if (fabs(m.rows[row][col]) > fabs(m.rows[best][col])) {
+          best = row;
+        }
+      }
+      if (best != col) {
+        // Swap rows x, best
+        std::swap(m.rows[col], m.rows[best]);
+        std::swap(ret.rows[col], ret.rows[best]);
+      }
+      if (m.rows[col][col] == 0.0f) {
+        // Failed, shouldn't happen.
+        NOTREACHED();
+        return ret;
+      }
+      float mult = 1.0f / m.rows[col][col];
+      for (int col2 = 0; col2 < 4; col2++) {
+        m.rows[col][col2] *= mult;
+        ret.rows[col][col2] *= mult;
+      }
+      m.rows[col][col] = 1.0f;
+    }
+    for (int row = 0; row < 3; row++) {
+      if (row == col)
+        continue;
+      float mult = m.rows[row][col];
+      if (mult == 0.0f)
+        continue;
+
+      for (int col2 = 0; col2 < 4; col2++) {
+        m.rows[row][col2] -= m.rows[col][col2] * mult;
+        ret.rows[row][col2] -= ret.rows[col][col2] * mult;
+      }
+      m.rows[row][col] = 0.0f;
+    }
+  }
+  return ret;
+}
+
 double GetContrastRatio(SkColor color_a, SkColor color_b) {
   return GetContrastRatio(GetRelativeLuminance(color_a),
                           GetRelativeLuminance(color_b));