1 /* 2 * Copyright (c) 2015 The WebM project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #include <limits.h> 12 #include <math.h> 13 14 #include "vp9/common/vp9_blockd.h" 15 #include "vp9/encoder/vp9_encoder.h" 16 #include "vp9/encoder/vp9_skin_detection.h" 17 18 // Fixed-point skin color model parameters. 19 static const int skin_mean[2] = {7463, 9614}; // q6 20 static const int skin_inv_cov[4] = {4107, 1663, 1663, 2157}; // q16 21 static const int skin_threshold = 1570636; // q18 22 23 // Thresholds on luminance. 24 static const int y_low = 20; 25 static const int y_high = 220; 26 27 // Evaluates the Mahalanobis distance measure for the input CbCr values. 28 static int evaluate_skin_color_difference(int cb, int cr) { 29 const int cb_q6 = cb << 6; 30 const int cr_q6 = cr << 6; 31 const int cb_diff_q12 = (cb_q6 - skin_mean[0]) * (cb_q6 - skin_mean[0]); 32 const int cbcr_diff_q12 = (cb_q6 - skin_mean[0]) * (cr_q6 - skin_mean[1]); 33 const int cr_diff_q12 = (cr_q6 - skin_mean[1]) * (cr_q6 - skin_mean[1]); 34 const int cb_diff_q2 = (cb_diff_q12 + (1 << 9)) >> 10; 35 const int cbcr_diff_q2 = (cbcr_diff_q12 + (1 << 9)) >> 10; 36 const int cr_diff_q2 = (cr_diff_q12 + (1 << 9)) >> 10; 37 const int skin_diff = skin_inv_cov[0] * cb_diff_q2 + 38 skin_inv_cov[1] * cbcr_diff_q2 + 39 skin_inv_cov[2] * cbcr_diff_q2 + 40 skin_inv_cov[3] * cr_diff_q2; 41 return skin_diff; 42 } 43 44 int vp9_skin_pixel(const uint8_t y, const uint8_t cb, const uint8_t cr) { 45 if (y < y_low || y > y_high) 46 return 0; 47 else 48 return (evaluate_skin_color_difference(cb, cr) < skin_threshold); 49 } 50 51 #ifdef OUTPUT_YUV_SKINMAP 52 // For viewing skin map on input source. 53 void vp9_compute_skin_map(VP9_COMP *const cpi, FILE *yuv_skinmap_file) { 54 int i, j, mi_row, mi_col, num_bl; 55 VP9_COMMON *const cm = &cpi->common; 56 uint8_t *y; 57 const uint8_t *src_y = cpi->Source->y_buffer; 58 const uint8_t *src_u = cpi->Source->u_buffer; 59 const uint8_t *src_v = cpi->Source->v_buffer; 60 const int src_ystride = cpi->Source->y_stride; 61 const int src_uvstride = cpi->Source->uv_stride; 62 int y_bsize = 16; // Use 8x8 or 16x16. 63 int uv_bsize = y_bsize >> 1; 64 int ypos = y_bsize >> 1; 65 int uvpos = uv_bsize >> 1; 66 int shy = (y_bsize == 8) ? 3 : 4; 67 int shuv = shy - 1; 68 int fac = y_bsize / 8; 69 // Use center pixel or average of center 2x2 pixels. 70 int mode_filter = 1; 71 YV12_BUFFER_CONFIG skinmap; 72 memset(&skinmap, 0, sizeof(YV12_BUFFER_CONFIG)); 73 if (vpx_alloc_frame_buffer(&skinmap, cm->width, cm->height, 74 cm->subsampling_x, cm->subsampling_y, 75 VP9_ENC_BORDER_IN_PIXELS, cm->byte_alignment)) { 76 vpx_free_frame_buffer(&skinmap); 77 return; 78 } 79 memset(skinmap.buffer_alloc, 128, skinmap.frame_size); 80 y = skinmap.y_buffer; 81 // Loop through blocks and set skin map based on center pixel of block. 82 // Set y to white for skin block, otherwise set to source with gray scale. 83 // Ignore rightmost/bottom boundary blocks. 84 for (mi_row = 0; mi_row < cm->mi_rows - 1; mi_row += fac) { 85 num_bl = 0; 86 for (mi_col = 0; mi_col < cm->mi_cols - 1; mi_col += fac) { 87 // Select pixel for each block for skin detection. 88 // Use center pixel, or 2x2 average at center. 89 uint8_t ysource = src_y[ypos * src_ystride + ypos]; 90 uint8_t usource = src_u[uvpos * src_uvstride + uvpos]; 91 uint8_t vsource = src_v[uvpos * src_uvstride + uvpos]; 92 uint8_t ysource2 = src_y[(ypos + 1) * src_ystride + ypos]; 93 uint8_t usource2 = src_u[(uvpos + 1) * src_uvstride + uvpos]; 94 uint8_t vsource2 = src_v[(uvpos + 1) * src_uvstride + uvpos]; 95 uint8_t ysource3 = src_y[ypos * src_ystride + (ypos + 1)]; 96 uint8_t usource3 = src_u[uvpos * src_uvstride + (uvpos + 1)]; 97 uint8_t vsource3 = src_v[uvpos * src_uvstride + (uvpos + 1)]; 98 uint8_t ysource4 = src_y[(ypos + 1) * src_ystride + (ypos + 1)]; 99 uint8_t usource4 = src_u[(uvpos + 1) * src_uvstride + (uvpos + 1)]; 100 uint8_t vsource4 = src_v[(uvpos + 1) * src_uvstride + (uvpos + 1)]; 101 int is_skin = 0; 102 if (mode_filter == 1) { 103 ysource = (ysource + ysource2 + ysource3 + ysource4) >> 2; 104 usource = (usource + usource2 + usource3 + usource4) >> 2; 105 vsource = (vsource + vsource2 + vsource3 + vsource4) >> 2; 106 } 107 is_skin = vp9_skin_pixel(ysource, usource, vsource); 108 for (i = 0; i < y_bsize; i++) { 109 for (j = 0; j < y_bsize; j++) { 110 if (is_skin) 111 y[i * src_ystride + j] = 255; 112 else 113 y[i * src_ystride + j] = src_y[i * src_ystride + j]; 114 } 115 } 116 num_bl++; 117 y += y_bsize; 118 src_y += y_bsize; 119 src_u += uv_bsize; 120 src_v += uv_bsize; 121 } 122 y += (src_ystride << shy) - (num_bl << shy); 123 src_y += (src_ystride << shy) - (num_bl << shy); 124 src_u += (src_uvstride << shuv) - (num_bl << shuv); 125 src_v += (src_uvstride << shuv) - (num_bl << shuv); 126 } 127 vp9_write_yuv_frame_420(&skinmap, yuv_skinmap_file); 128 vpx_free_frame_buffer(&skinmap); 129 } 130 #endif 131
