ref: 9aa083d164e0d39086aa0c83f0d1a0d0f0d1ba61
dir: /vp10/encoder/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 <limits.h> #include <math.h> #include "vp10/common/blockd.h" #include "vp10/encoder/encoder.h" #include "vp10/encoder/skin_detection.h" // Fixed-point skin color model parameters. static const int skin_mean[2] = {7463, 9614}; // q6 static const int skin_inv_cov[4] = {4107, 1663, 1663, 2157}; // q16 static const int skin_threshold = 1570636; // q18 // Thresholds on luminance. static const int y_low = 20; static const int y_high = 220; // Evaluates the Mahalanobis distance measure for the input CbCr values. static int evaluate_skin_color_difference(int cb, int cr) { const int cb_q6 = cb << 6; const int cr_q6 = cr << 6; const int cb_diff_q12 = (cb_q6 - skin_mean[0]) * (cb_q6 - skin_mean[0]); const int cbcr_diff_q12 = (cb_q6 - skin_mean[0]) * (cr_q6 - skin_mean[1]); const int cr_diff_q12 = (cr_q6 - skin_mean[1]) * (cr_q6 - skin_mean[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; } int vp10_skin_pixel(const uint8_t y, const uint8_t cb, const uint8_t cr) { if (y < y_low || y > y_high) return 0; else return (evaluate_skin_color_difference(cb, cr) < skin_threshold); } #ifdef OUTPUT_YUV_SKINMAP // For viewing skin map on input source. void vp10_compute_skin_map(VP10_COMP *const cpi, FILE *yuv_skinmap_file) { int i, j, mi_row, mi_col; VP10_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(YV12_BUFFER_CONFIG)); if (vpx_alloc_frame_buffer(&skinmap, cm->width, cm->height, cm->subsampling_x, cm->subsampling_y, VP9_ENC_BORDER_IN_PIXELS, cm->byte_alignment)) { vpx_free_frame_buffer(&skinmap); return; } memset(skinmap.buffer_alloc, 128, skinmap.frame_size); y = skinmap.y_buffer; // Loop through 8x8 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 (mi_row = 0; mi_row < cm->mi_rows - 1; ++mi_row) { for (mi_col = 0; mi_col < cm->mi_cols - 1; ++mi_col) { // Use middle pixel for each 8x8 block for skin detection. // If middle pixel is skin, assign whole 8x8 block to skin. const uint8_t ysource = src_y[4 * src_ystride + 4]; const uint8_t usource = src_u[2 * src_uvstride + 2]; const uint8_t vsource = src_v[2 * src_uvstride + 2]; const int is_skin = vp10_skin_pixel(ysource, usource, vsource); for (i = 0; i < 8; i++) { for (j = 0; j < 8; j++) { if (is_skin) y[i * src_ystride + j] = 255; else y[i * src_ystride + j] = src_y[i * src_ystride + j]; } } y += 8; src_y += 8; src_u += 4; src_v += 4; } y += (src_ystride << 3) - ((cm->mi_cols - 1) << 3); src_y += (src_ystride << 3) - ((cm->mi_cols - 1) << 3); src_u += (src_uvstride << 2) - ((cm->mi_cols - 1) << 2); src_v += (src_uvstride << 2) - ((cm->mi_cols - 1) << 2); } vp10_write_yuv_frame_420(&skinmap, yuv_skinmap_file); vpx_free_frame_buffer(&skinmap); } #endif