ref: c12d1d9b982e8717d2d7cabe3230105948bd3b7a
dir: /vp8/common/skin_detection.c/
/* * Copyright (c) 2015 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 "vp8/common/skin_detection.h" #include "vp8/common/alloccommon.h" #include "vpx_dsp/vpx_dsp_common.h" #include "vpx_mem/vpx_mem.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 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 skin_pixel(int y, int cb, int cr, int motion) { if (y < y_low || y > y_high) { return 0; } else { if (MODEL_MODE == 0) { return (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 = 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; } } } int compute_skin_block(const uint8_t *y, const uint8_t *u, const uint8_t *v, int stride, int strideuv, int consec_zeromv, int curr_motion_magn) { // No skin if block has been zero/small motion for long consecutive time. if (consec_zeromv > 60 && curr_motion_magn == 0) { return 0; } else { int motion = 1; // Take the average of center 2x2 pixels. const int ysource = (y[7 * stride + 7] + y[7 * stride + 8] + y[8 * stride + 7] + y[8 * stride + 8]) >> 2; const int usource = (u[3 * strideuv + 3] + u[3 * strideuv + 4] + u[4 * strideuv + 3] + u[4 * strideuv + 4]) >> 2; const int vsource = (v[3 * strideuv + 3] + v[3 * strideuv + 4] + v[4 * strideuv + 3] + v[4 * strideuv + 4]) >> 2; if (consec_zeromv > 25 && curr_motion_magn == 0) motion = 0; return skin_pixel(ysource, usource, vsource, motion); } } #ifdef OUTPUT_YUV_SKINMAP // For viewing skin map on input source. void compute_skin_map(VP8_COMP *const cpi, FILE *yuv_skinmap_file) { int i, j, mb_row, mb_col, num_bl; VP8_COMMON *const cm = &cpi->common; uint8_t *y; const uint8_t *src_y = cpi->Source->y_buffer; const uint8_t *src_u = cpi->Source->u_buffer; const uint8_t *src_v = cpi->Source->v_buffer; const int src_ystride = cpi->Source->y_stride; const int src_uvstride = cpi->Source->uv_stride; YV12_BUFFER_CONFIG skinmap; memset(&skinmap, 0, sizeof(skinmap)); if (vp8_yv12_alloc_frame_buffer(&skinmap, cm->Width, cm->Height, VP8BORDERINPIXELS) < 0) { vpx_free_frame_buffer(&skinmap); return; } memset(skinmap.buffer_alloc, 128, skinmap.frame_size); y = skinmap.y_buffer; // Loop through blocks and set skin map based on center pixel of block. // Set y to white for skin block, otherwise set to source with gray scale. // Ignore rightmost/bottom boundary blocks. for (mb_row = 0; mb_row < cm->mb_rows; mb_row += 1) { num_bl = 0; for (mb_col = 0; mb_col < cm->mb_cols; mb_col += 1) { int is_skin = 0; int consec_zeromv = 0; const int bl_index = mb_row * cm->mb_cols + mb_col; const int bl_index1 = bl_index + 1; const int bl_index2 = bl_index + cm->mb_cols; const int bl_index3 = bl_index2 + 1; consec_zeromv = VPXMIN(cpi->consec_zero_last[bl_index], VPXMIN(cpi->consec_zero_last[bl_index1], VPXMIN(cpi->consec_zero_last[bl_index2], cpi->consec_zero_last[bl_index3]))); is_skin = compute_skin_block(src_y, src_u, src_v, src_ystride, src_uvstride, consec_zeromv, 0); for (i = 0; i < 16; i++) { for (j = 0; j < 16; j++) { if (is_skin) y[i * src_ystride + j] = 255; else y[i * src_ystride + j] = src_y[i * src_ystride + j]; } } num_bl++; y += 16; src_y += 16; src_u += 8; src_v += 8; } y += (src_ystride << 4) - (num_bl << 4); src_y += (src_ystride << 4) - (num_bl << 4); src_u += (src_uvstride << 3) - (num_bl << 3); src_v += (src_uvstride << 3) - (num_bl << 3); } vp8_write_yuv_frame(yuv_skinmap_file, &skinmap); vpx_free_frame_buffer(&skinmap); } #endif // OUTPUT_YUV_SKINMAP