diff options
Diffstat (limited to 'media/libvpx/vp9/encoder/vp9_skin_detection.c')
| -rw-r--r-- | media/libvpx/vp9/encoder/vp9_skin_detection.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/media/libvpx/vp9/encoder/vp9_skin_detection.c b/media/libvpx/vp9/encoder/vp9_skin_detection.c new file mode 100644 index 000000000..1cb066283 --- /dev/null +++ b/media/libvpx/vp9/encoder/vp9_skin_detection.c @@ -0,0 +1,104 @@ +/* + * 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" + +// 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 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 + return (evaluate_skin_color_difference(cb, cr) < skin_threshold); +} + +#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; + 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; + YV12_BUFFER_CONFIG skinmap; + memset(&skinmap, 0, sizeof(YV12_BUFFER_CONFIG)); + if (vp9_alloc_frame_buffer(&skinmap, cm->width, cm->height, + cm->subsampling_x, cm->subsampling_y, + VP9_ENC_BORDER_IN_PIXELS, cm->byte_alignment)) { + vp9_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 = vp9_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); + } + vp9_write_yuv_frame_420(&skinmap, yuv_skinmap_file); + vp9_free_frame_buffer(&skinmap); +} +#endif |