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//
// Copyright © 2020 Arm Ltd and Contributors. All rights reserved.
// SPDX-License-Identifier: MIT
//
#include "SSDResultDecoder.hpp"
#include <cassert>
#include <algorithm>
#include <cmath>
#include <stdexcept>
namespace od
{
DetectedObjects SSDResultDecoder::Decode(const common::InferenceResults<float>& networkResults,
const common::Size& outputFrameSize,
const common::Size& resizedFrameSize,
const std::vector<std::string>& labels)
{
// SSD network outputs 4 tensors: bounding boxes, labels, probabilities, number of detections.
if (networkResults.size() != 4)
{
throw std::runtime_error("Number of outputs from SSD model doesn't equal 4");
}
DetectedObjects detectedObjects;
const int numDetections = static_cast<int>(std::lround(networkResults[3][0]));
double longEdgeInput = std::max(resizedFrameSize.m_Width, resizedFrameSize.m_Height);
double longEdgeOutput = std::max(outputFrameSize.m_Width, outputFrameSize.m_Height);
const double resizeFactor = longEdgeOutput/longEdgeInput;
for (int i=0; i<numDetections; ++i)
{
if (networkResults[2][i] > m_objectThreshold)
{
DetectedObject detectedObject;
detectedObject.SetScore(networkResults[2][i]);
auto classId = std::lround(networkResults[1][i]);
if (classId < labels.size())
{
detectedObject.SetLabel(labels[classId]);
}
else
{
detectedObject.SetLabel(std::to_string(classId));
}
detectedObject.SetId(classId);
// Convert SSD bbox outputs (ratios of image size) to pixel values.
double topLeftY = networkResults[0][i*4 + 0] * resizedFrameSize.m_Height;
double topLeftX = networkResults[0][i*4 + 1] * resizedFrameSize.m_Width;
double botRightY = networkResults[0][i*4 + 2] * resizedFrameSize.m_Height;
double botRightX = networkResults[0][i*4 + 3] * resizedFrameSize.m_Width;
// Scale the coordinates to output frame size.
topLeftY *= resizeFactor;
topLeftX *= resizeFactor;
botRightY *= resizeFactor;
botRightX *= resizeFactor;
assert(botRightX > topLeftX);
assert(botRightY > topLeftY);
// Internal BoundingBox stores box top left x,y and width, height.
detectedObject.SetBoundingBox({static_cast<int>(std::round(topLeftX)),
static_cast<int>(std::round(topLeftY)),
static_cast<unsigned int>(botRightX - topLeftX),
static_cast<unsigned int>(botRightY - topLeftY)});
detectedObjects.emplace_back(detectedObject);
}
}
return detectedObjects;
}
SSDResultDecoder::SSDResultDecoder(float ObjectThreshold) : m_objectThreshold(ObjectThreshold) {}
}// namespace od
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