Éanna Ó Catháin | 919c14e | 2020-09-14 17:36:49 +0100 | [diff] [blame] | 1 | // |
| 2 | // Copyright © 2020 Arm Ltd and Contributors. All rights reserved. |
| 3 | // SPDX-License-Identifier: MIT |
| 4 | // |
| 5 | #include "NonMaxSuppression.hpp" |
| 6 | |
| 7 | #include <algorithm> |
| 8 | |
| 9 | namespace od |
| 10 | { |
| 11 | |
| 12 | static std::vector<unsigned int> GenerateRangeK(unsigned int k) |
| 13 | { |
| 14 | std::vector<unsigned int> range(k); |
| 15 | std::iota(range.begin(), range.end(), 0); |
| 16 | return range; |
| 17 | } |
| 18 | |
| 19 | |
| 20 | /** |
| 21 | * @brief Returns the intersection over union for two bounding boxes |
| 22 | * |
| 23 | * @param[in] First detect containing bounding box. |
| 24 | * @param[in] Second detect containing bounding box. |
| 25 | * @return Calculated intersection over union. |
| 26 | * |
| 27 | */ |
| 28 | static double IntersectionOverUnion(DetectedObject& detect1, DetectedObject& detect2) |
| 29 | { |
| 30 | uint32_t area1 = (detect1.GetBoundingBox().GetHeight() * detect1.GetBoundingBox().GetWidth()); |
| 31 | uint32_t area2 = (detect2.GetBoundingBox().GetHeight() * detect2.GetBoundingBox().GetWidth()); |
| 32 | |
| 33 | float yMinIntersection = std::max(detect1.GetBoundingBox().GetY(), detect2.GetBoundingBox().GetY()); |
| 34 | float xMinIntersection = std::max(detect1.GetBoundingBox().GetX(), detect2.GetBoundingBox().GetX()); |
| 35 | |
| 36 | float yMaxIntersection = std::min(detect1.GetBoundingBox().GetY() + detect1.GetBoundingBox().GetHeight(), |
| 37 | detect2.GetBoundingBox().GetY() + detect2.GetBoundingBox().GetHeight()); |
| 38 | float xMaxIntersection = std::min(detect1.GetBoundingBox().GetX() + detect1.GetBoundingBox().GetWidth(), |
| 39 | detect2.GetBoundingBox().GetX() + detect2.GetBoundingBox().GetWidth()); |
| 40 | |
| 41 | double areaIntersection = std::max(yMaxIntersection - yMinIntersection, 0.0f) * |
| 42 | std::max(xMaxIntersection - xMinIntersection, 0.0f); |
| 43 | double areaUnion = area1 + area2 - areaIntersection; |
| 44 | |
| 45 | return areaIntersection / areaUnion; |
| 46 | } |
| 47 | |
| 48 | std::vector<int> NonMaxSuppression(DetectedObjects& inputDetections, float iouThresh) |
| 49 | { |
| 50 | // Sort indicies of detections by highest score to lowest. |
| 51 | std::vector<unsigned int> sortedIndicies = GenerateRangeK(inputDetections.size()); |
| 52 | std::sort(sortedIndicies.begin(), sortedIndicies.end(), |
| 53 | [&inputDetections](int idx1, int idx2) |
| 54 | { |
| 55 | return inputDetections[idx1].GetScore() > inputDetections[idx2].GetScore(); |
| 56 | }); |
| 57 | |
| 58 | std::vector<bool> visited(inputDetections.size(), false); |
| 59 | std::vector<int> outputIndiciesAfterNMS; |
| 60 | |
| 61 | for (int i=0; i < inputDetections.size(); ++i) |
| 62 | { |
| 63 | // Each new unvisited detect should be kept. |
| 64 | if (!visited[sortedIndicies[i]]) |
| 65 | { |
| 66 | outputIndiciesAfterNMS.emplace_back(sortedIndicies[i]); |
| 67 | visited[sortedIndicies[i]] = true; |
| 68 | } |
| 69 | |
| 70 | // Look for detections to suppress. |
| 71 | for (int j=i+1; j<inputDetections.size(); ++j) |
| 72 | { |
| 73 | // Skip if already kept or suppressed. |
| 74 | if (!visited[sortedIndicies[j]]) |
| 75 | { |
| 76 | // Detects must have the same label to be suppressed. |
| 77 | if (inputDetections[sortedIndicies[j]].GetLabel() == inputDetections[sortedIndicies[i]].GetLabel()) |
| 78 | { |
| 79 | auto iou = IntersectionOverUnion(inputDetections[sortedIndicies[i]], |
| 80 | inputDetections[sortedIndicies[j]]); |
| 81 | if (iou > iouThresh) |
| 82 | { |
| 83 | visited[sortedIndicies[j]] = true; |
| 84 | } |
| 85 | } |
| 86 | } |
| 87 | } |
| 88 | } |
| 89 | return outputIndiciesAfterNMS; |
| 90 | } |
| 91 | |
| 92 | } // namespace od |