1 files changed, 79 insertions, 0 deletions
diff --git a/media/libvpx/libvpx/vpx_dsp/skin_detection.c b/media/libvpx/libvpx/vpx_dsp/skin_detection.c
new file mode 100644
index 0000000000..bbbb6c3a17
--- /dev/null
+++ b/media/libvpx/libvpx/vpx_dsp/skin_detection.c
@@ -0,0 +1,79 @@
+/*
+ *  Copyright (c) 2017 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "vpx_dsp/skin_detection.h"
+
+#define MODEL_MODE 1
+
+// Fixed-point skin color model parameters.
+static const int skin_mean[5][2] = { { 7463, 9614 },
+                                     { 6400, 10240 },
+                                     { 7040, 10240 },
+                                     { 8320, 9280 },
+                                     { 6800, 9614 } };
+static const int skin_inv_cov[4] = { 4107, 1663, 1663, 2157 };  // q16
+static const int skin_threshold[6] = { 1570636, 1400000, 800000,
+                                       800000,  800000,  800000 };  // q18
+// Thresholds on luminance.
+static const int y_low = 40;
+static const int y_high = 220;
+
+// Evaluates the Mahalanobis distance measure for the input CbCr values.
+static int vpx_evaluate_skin_color_difference(const int cb, const int cr,
+                                              const int idx) {
+  const int cb_q6 = cb << 6;
+  const int cr_q6 = cr << 6;
+  const int cb_diff_q12 =
+      (cb_q6 - skin_mean[idx][0]) * (cb_q6 - skin_mean[idx][0]);
+  const int cbcr_diff_q12 =
+      (cb_q6 - skin_mean[idx][0]) * (cr_q6 - skin_mean[idx][1]);
+  const int cr_diff_q12 =
+      (cr_q6 - skin_mean[idx][1]) * (cr_q6 - skin_mean[idx][1]);
+  const int cb_diff_q2 = (cb_diff_q12 + (1 << 9)) >> 10;
+  const int cbcr_diff_q2 = (cbcr_diff_q12 + (1 << 9)) >> 10;
+  const int cr_diff_q2 = (cr_diff_q12 + (1 << 9)) >> 10;
+  const int skin_diff =
+      skin_inv_cov[0] * cb_diff_q2 + skin_inv_cov[1] * cbcr_diff_q2 +
+      skin_inv_cov[2] * cbcr_diff_q2 + skin_inv_cov[3] * cr_diff_q2;
+  return skin_diff;
+}
+
+// Checks if the input yCbCr values corresponds to skin color.
+int vpx_skin_pixel(const int y, const int cb, const int cr, int motion) {
+  if (y < y_low || y > y_high) {
+    return 0;
+  } else if (MODEL_MODE == 0) {
+    return (vpx_evaluate_skin_color_difference(cb, cr, 0) < skin_threshold[0]);
+  } else {
+    int i = 0;
+    // Exit on grey.
+    if (cb == 128 && cr == 128) return 0;
+    // Exit on very strong cb.
+    if (cb > 150 && cr < 110) return 0;
+    for (; i < 5; ++i) {
+      int skin_color_diff = vpx_evaluate_skin_color_difference(cb, cr, i);
+      if (skin_color_diff < skin_threshold[i + 1]) {
+        if (y < 60 && skin_color_diff > 3 * (skin_threshold[i + 1] >> 2)) {
+          return 0;
+        } else if (motion == 0 &&
+                   skin_color_diff > (skin_threshold[i + 1] >> 1)) {
+          return 0;
+        } else {
+          return 1;
+        }
+      }
+      // Exit if difference is much large than the threshold.
+      if (skin_color_diff > (skin_threshold[i + 1] << 3)) {
+        return 0;
+      }
+    }
+    return 0;
+  }
+}