ref: 268ec8dcfbbd23339eea06805aff68a28510a3cd
dir: /vp9/encoder/vp9_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 "vp9/common/vp9_blockd.h" #include "vp9/encoder/vp9_encoder.h" #include "vp9/encoder/vp9_skin_detection.h" #define MODEL_MODE 0 // 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(int cb, int cr, 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; } int vp9_skin_pixel(const uint8_t y, const uint8_t cb, const uint8_t cr) { 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; // Exit on (another) low luminance threshold if either color is high. if (y < 50 && (cb > 140 || cr > 140)) return 0; for (; i < 5; i++) { if (evaluate_skin_color_difference(cb, cr, i) < skin_threshold[i + 1]) { return 1; } // Exit if difference is much large than the threshold. if (evaluate_skin_color_difference(cb, cr, i) > (skin_threshold[i + 1] << 3)) { return 0; } } return 0; } } } int vp9_compute_skin_block(const uint8_t *y, const uint8_t *u, const uint8_t *v, int stride, int strideuv, int bsize) { // Take center pixel in block to determine is_skin. const int y_width_shift = (4 << b_width_log2_lookup[bsize]) >> 1; const int y_height_shift = (4 << b_height_log2_lookup[bsize]) >> 1; const int uv_width_shift = y_width_shift >> 1; const int uv_height_shift = y_height_shift >> 1; const uint8_t ysource = y[y_height_shift * stride + y_width_shift]; const uint8_t usource = u[uv_height_shift * strideuv + uv_width_shift]; const uint8_t vsource = v[uv_height_shift * strideuv + uv_width_shift]; return vp9_skin_pixel(ysource, usource, vsource); } #ifdef OUTPUT_YUV_SKINMAP // For viewing skin map on input source. void vp9_compute_skin_map(VP9_COMP *const cpi, FILE *yuv_skinmap_file) { int i, j, mi_row, mi_col, num_bl; VP9_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; int y_bsize = 16; // Use 8x8 or 16x16. int uv_bsize = y_bsize >> 1; int ypos = y_bsize >> 1; int uvpos = uv_bsize >> 1; int shy = (y_bsize == 8) ? 3 : 4; int shuv = shy - 1; int fac = y_bsize / 8; // Use center pixel or average of center 2x2 pixels. int mode_filter = 1; 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 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 += fac) { num_bl = 0; for (mi_col = 0; mi_col < cm->mi_cols - 1; mi_col += fac) { // Select pixel for each block for skin detection. // Use center pixel, or 2x2 average at center. uint8_t ysource = src_y[ypos * src_ystride + ypos]; uint8_t usource = src_u[uvpos * src_uvstride + uvpos]; uint8_t vsource = src_v[uvpos * src_uvstride + uvpos]; uint8_t ysource2 = src_y[(ypos + 1) * src_ystride + ypos]; uint8_t usource2 = src_u[(uvpos + 1) * src_uvstride + uvpos]; uint8_t vsource2 = src_v[(uvpos + 1) * src_uvstride + uvpos]; uint8_t ysource3 = src_y[ypos * src_ystride + (ypos + 1)]; uint8_t usource3 = src_u[uvpos * src_uvstride + (uvpos + 1)]; uint8_t vsource3 = src_v[uvpos * src_uvstride + (uvpos + 1)]; uint8_t ysource4 = src_y[(ypos + 1) * src_ystride + (ypos + 1)]; uint8_t usource4 = src_u[(uvpos + 1) * src_uvstride + (uvpos + 1)]; uint8_t vsource4 = src_v[(uvpos + 1) * src_uvstride + (uvpos + 1)]; int is_skin = 0; if (mode_filter == 1) { ysource = (ysource + ysource2 + ysource3 + ysource4) >> 2; usource = (usource + usource2 + usource3 + usource4) >> 2; vsource = (vsource + vsource2 + vsource3 + vsource4) >> 2; } is_skin = vp9_skin_pixel(ysource, usource, vsource); for (i = 0; i < y_bsize; i++) { for (j = 0; j < y_bsize; 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 += y_bsize; src_y += y_bsize; src_u += uv_bsize; src_v += uv_bsize; } y += (src_ystride << shy) - (num_bl << shy); src_y += (src_ystride << shy) - (num_bl << shy); src_u += (src_uvstride << shuv) - (num_bl << shuv); src_v += (src_uvstride << shuv) - (num_bl << shuv); } vp9_write_yuv_frame_420(&skinmap, yuv_skinmap_file); vpx_free_frame_buffer(&skinmap); } #endif