ref: f835ab76082e8ea2e04901f1b9746c65e56f4218
dir: /vpx_dsp/skin_detection.c/
/* * 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; } }