/* * Copyright (c) 2016 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 #include #include #include #include "av1/encoder/corner_match.h" #define MATCH_SZ 15 #define MATCH_SZ_BY2 ((MATCH_SZ - 1) / 2) #define MATCH_SZ_SQ (MATCH_SZ * MATCH_SZ) #define SEARCH_SZ 9 #define SEARCH_SZ_BY2 ((SEARCH_SZ - 1) / 2) #define THRESHOLD_NCC 0.80 static double compute_variance(unsigned char *im, int stride, int x, int y, double *mean) { double sum = 0.0; double sumsq = 0.0; double var; int i, j; for (i = 0; i < MATCH_SZ; ++i) for (j = 0; j < MATCH_SZ; ++j) { sum += im[(i + y - MATCH_SZ_BY2) * stride + (j + x - MATCH_SZ_BY2)]; sumsq += im[(i + y - MATCH_SZ_BY2) * stride + (j + x - MATCH_SZ_BY2)] * im[(i + y - MATCH_SZ_BY2) * stride + (j + x - MATCH_SZ_BY2)]; } var = (sumsq * MATCH_SZ_SQ - sum * sum) / (MATCH_SZ_SQ * MATCH_SZ_SQ); if (mean) *mean = sum / MATCH_SZ_SQ; return var; } static double compute_cross_correlation(unsigned char *im1, int stride1, int x1, int y1, unsigned char *im2, int stride2, int x2, int y2) { double sum1 = 0; double sum2 = 0; double cross = 0; double corr; int i, j; for (i = 0; i < MATCH_SZ; ++i) for (j = 0; j < MATCH_SZ; ++j) { sum1 += im1[(i + y1 - MATCH_SZ_BY2) * stride1 + (j + x1 - MATCH_SZ_BY2)]; sum2 += im2[(i + y2 - MATCH_SZ_BY2) * stride2 + (j + x2 - MATCH_SZ_BY2)]; cross += im1[(i + y1 - MATCH_SZ_BY2) * stride1 + (j + x1 - MATCH_SZ_BY2)] * im2[(i + y2 - MATCH_SZ_BY2) * stride2 + (j + x2 - MATCH_SZ_BY2)]; } corr = (cross * MATCH_SZ_SQ - sum1 * sum2) / (MATCH_SZ_SQ * MATCH_SZ_SQ); return corr; } static int is_eligible_point(double pointx, double pointy, int width, int height) { return (pointx >= MATCH_SZ_BY2 && pointy >= MATCH_SZ_BY2 && pointx + MATCH_SZ_BY2 < width && pointy + MATCH_SZ_BY2 < height); } static int is_eligible_distance(double point1x, double point1y, double point2x, double point2y, int width, int height) { const int thresh = (width < height ? height : width) >> 4; return ((point1x - point2x) * (point1x - point2x) + (point1y - point2y) * (point1y - point2y)) <= thresh * thresh; } static void improve_correspondence(unsigned char *frm, unsigned char *ref, int width, int height, int frm_stride, int ref_stride, Correspondence *correspondences, int num_correspondences) { int i; for (i = 0; i < num_correspondences; ++i) { double template_norm = compute_variance(frm, frm_stride, (int)correspondences[i].x, (int)correspondences[i].y, NULL); int x, y, best_x = 0, best_y = 0; double best_match_ncc = 0.0; for (y = -SEARCH_SZ_BY2; y <= SEARCH_SZ_BY2; ++y) { for (x = -SEARCH_SZ_BY2; x <= SEARCH_SZ_BY2; ++x) { double match_ncc; double subimage_norm; if (!is_eligible_point((int)correspondences[i].rx + x, (int)correspondences[i].ry + y, width, height)) continue; if (!is_eligible_distance( (int)correspondences[i].x, (int)correspondences[i].y, (int)correspondences[i].rx + x, (int)correspondences[i].ry + y, width, height)) continue; subimage_norm = compute_variance(ref, ref_stride, (int)correspondences[i].rx + x, (int)correspondences[i].ry + y, NULL); match_ncc = compute_cross_correlation( frm, frm_stride, (int)correspondences[i].x, (int)correspondences[i].y, ref, ref_stride, (int)correspondences[i].rx + x, (int)correspondences[i].ry + y) / sqrt(template_norm * subimage_norm); if (match_ncc > best_match_ncc) { best_match_ncc = match_ncc; best_y = y; best_x = x; } } } correspondences[i].rx += (double)best_x; correspondences[i].ry += (double)best_y; } for (i = 0; i < num_correspondences; ++i) { double template_norm = compute_variance(ref, ref_stride, (int)correspondences[i].rx, (int)correspondences[i].ry, NULL); int x, y, best_x = 0, best_y = 0; double best_match_ncc = 0.0; for (y = -SEARCH_SZ_BY2; y <= SEARCH_SZ_BY2; ++y) for (x = -SEARCH_SZ_BY2; x <= SEARCH_SZ_BY2; ++x) { double match_ncc; double subimage_norm; if (!is_eligible_point((int)correspondences[i].x + x, (int)correspondences[i].y + y, width, height)) continue; if (!is_eligible_distance((int)correspondences[i].x + x, (int)correspondences[i].y + y, (int)correspondences[i].rx, (int)correspondences[i].ry, width, height)) continue; subimage_norm = compute_variance(frm, frm_stride, (int)correspondences[i].x + x, (int)correspondences[i].y + y, NULL); match_ncc = compute_cross_correlation( frm, frm_stride, (int)correspondences[i].x + x, (int)correspondences[i].y + y, ref, ref_stride, (int)correspondences[i].rx, (int)correspondences[i].ry) / sqrt(template_norm * subimage_norm); if (match_ncc > best_match_ncc) { best_match_ncc = match_ncc; best_y = y; best_x = x; } } correspondences[i].x += best_x; correspondences[i].y += best_y; } } int determine_correspondence(unsigned char *frm, int *frm_corners, int num_frm_corners, unsigned char *ref, int *ref_corners, int num_ref_corners, int width, int height, int frm_stride, int ref_stride, double *correspondence_pts) { // TODO(sarahparker) Improve this to include 2-way match int i, j; Correspondence *correspondences = (Correspondence *)correspondence_pts; int num_correspondences = 0; for (i = 0; i < num_frm_corners; ++i) { double best_match_ncc = 0.0; double template_norm; int best_match_j = -1; if (!is_eligible_point(frm_corners[2 * i], frm_corners[2 * i + 1], width, height)) continue; template_norm = compute_variance(frm, frm_stride, frm_corners[2 * i], frm_corners[2 * i + 1], NULL); for (j = 0; j < num_ref_corners; ++j) { double match_ncc; double subimage_norm; if (!is_eligible_point(ref_corners[2 * j], ref_corners[2 * j + 1], width, height)) continue; if (!is_eligible_distance(frm_corners[2 * i], frm_corners[2 * i + 1], ref_corners[2 * j], ref_corners[2 * j + 1], width, height)) continue; subimage_norm = compute_variance(ref, ref_stride, ref_corners[2 * j], ref_corners[2 * j + 1], NULL); match_ncc = compute_cross_correlation(frm, frm_stride, frm_corners[2 * i], frm_corners[2 * i + 1], ref, ref_stride, ref_corners[2 * j], ref_corners[2 * j + 1]) / sqrt(template_norm * subimage_norm); if (match_ncc > best_match_ncc) { best_match_ncc = match_ncc; best_match_j = j; } } if (best_match_ncc > THRESHOLD_NCC) { correspondences[num_correspondences].x = (double)frm_corners[2 * i]; correspondences[num_correspondences].y = (double)frm_corners[2 * i + 1]; correspondences[num_correspondences].rx = (double)ref_corners[2 * best_match_j]; correspondences[num_correspondences].ry = (double)ref_corners[2 * best_match_j + 1]; num_correspondences++; } } improve_correspondence(frm, ref, width, height, frm_stride, ref_stride, correspondences, num_correspondences); return num_correspondences; }