MLECO-2874: Move NMS out of the OD use_case

* Add ImageUtils
* Move image related code from UseCaseCommonUtils to ImageUtils
* Move NMS related code to ImageUtils
* Delete test specific ImageUtils and use new ImageUtils

Signed-off-by: Richard Burton <richard.burton@arm.com>
Change-Id: Icbf5dd9c6a941b0126ecdf69a0c9d9969f22729f

4 files changed, 246 insertions, 53 deletions

diff --git a/source/application/main/ImageUtils.cc b/source/application/main/ImageUtils.cc
new file mode 100644
index 0000000..31b9493
--- /dev/null
+++ b/source/application/main/ImageUtils.cc
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2022 Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "ImageUtils.hpp"
+
+#include <limits>
+
+namespace arm {
+namespace app {
+namespace image {
+
+    float Calculate1DOverlap(float x1Center, float width1, float x2Center, float width2)
+    {
+        float left_1 = x1Center - width1/2;
+        float left_2 = x2Center - width2/2;
+        float leftest = left_1 > left_2 ? left_1 : left_2;
+
+        float right_1 = x1Center + width1/2;
+        float right_2 = x2Center + width2/2;
+        float rightest = right_1 < right_2 ? right_1 : right_2;
+
+        return rightest - leftest;
+    }
+
+    float CalculateBoxIntersect(Box& box1, Box& box2)
+    {
+        float width = Calculate1DOverlap(box1.x, box1.w, box2.x, box2.w);
+        if (width < 0) {
+            return 0;
+        }
+        float height = Calculate1DOverlap(box1.y, box1.h, box2.y, box2.h);
+        if (height < 0) {
+            return 0;
+        }
+
+        float total_area = width*height;
+        return total_area;
+    }
+
+    float CalculateBoxUnion(Box& box1, Box& box2)
+    {
+        float boxes_intersection = CalculateBoxIntersect(box1, box2);
+        float boxes_union = box1.w * box1.h + box2.w * box2.h - boxes_intersection;
+        return boxes_union;
+    }
+
+    float CalculateBoxIOU(Box& box1, Box& box2)
+    {
+        float boxes_intersection = CalculateBoxIntersect(box1, box2);
+        if (boxes_intersection == 0) {
+            return 0;
+        }
+
+        float boxes_union = CalculateBoxUnion(box1, box2);
+        if (boxes_union == 0) {
+            return 0;
+        }
+
+        return boxes_intersection / boxes_union;
+    }
+
+    void CalculateNMS(std::forward_list<Detection>& detections, int classes, float iouThreshold)
+    {
+        int idxClass{0};
+        auto CompareProbs = [idxClass](Detection& prob1, Detection& prob2) {
+            return prob1.prob[idxClass] > prob2.prob[idxClass];
+        };
+
+        for (idxClass = 0; idxClass < classes; ++idxClass) {
+            detections.sort(CompareProbs);
+
+            for (auto it=detections.begin(); it != detections.end(); ++it) {
+                if (it->prob[idxClass] == 0) continue;
+                for (auto itc=std::next(it, 1); itc != detections.end(); ++itc) {
+                    if (itc->prob[idxClass] == 0) {
+                        continue;
+                    }
+                    if (CalculateBoxIOU(it->bbox, itc->bbox) > iouThreshold) {
+                        itc->prob[idxClass] = 0;
+                    }
+                }
+            }
+        }
+    }
+
+    void ConvertImgToInt8(void* data, const size_t kMaxImageSize)
+    {
+        auto* tmp_req_data = static_cast<uint8_t*>(data);
+        auto* tmp_signed_req_data = static_cast<int8_t*>(data);
+
+        for (size_t i = 0; i < kMaxImageSize; i++) {
+            tmp_signed_req_data[i] = (int8_t) (
+                    (int32_t) (tmp_req_data[i]) - 128);
+        }
+    }
+
+    void RgbToGrayscale(const uint8_t* srcPtr, uint8_t* dstPtr, const size_t dstImgSz)
+    {
+        const float R = 0.299;
+        const float G = 0.587;
+        const float B = 0.114;
+        for (size_t i = 0; i < dstImgSz; ++i, srcPtr += 3) {
+            uint32_t  int_gray = R * (*srcPtr) +
+                                 G * (*(srcPtr + 1)) +
+                                 B * (*(srcPtr + 2));
+            *dstPtr++ = int_gray <= std::numeric_limits<uint8_t>::max() ?
+                        int_gray : std::numeric_limits<uint8_t>::max();
+        }
+    }
+
+} /* namespace image */
+} /* namespace app */
+} /* namespace arm */
\ No newline at end of file
diff --git a/source/application/main/UseCaseCommonUtils.cc b/source/application/main/UseCaseCommonUtils.cc
index dd9a32d..d439446 100644
--- a/source/application/main/UseCaseCommonUtils.cc
+++ b/source/application/main/UseCaseCommonUtils.cc
@@ -15,6 +15,7 @@
  * limitations under the License.
  */
 #include "UseCaseCommonUtils.hpp"
+#include "ImageUtils.hpp"
 #include "InputFiles.hpp"
 #include "log_macros.h"
 
@@ -35,19 +36,10 @@ void DisplayCommonMenu()
     fflush(stdout);
 }
 
-void image::ConvertImgToInt8(void* data, const size_t kMaxImageSize)
-{
-    auto* tmp_req_data = static_cast<uint8_t *>(data);
-    auto* tmp_signed_req_data = static_cast<int8_t *>(data);
 
-    for (size_t i = 0; i < kMaxImageSize; i++) {
-        tmp_signed_req_data[i] = (int8_t) (
-            (int32_t) (tmp_req_data[i]) - 128);
-    }
-}
 
 
-bool image::PresentInferenceResult(
+bool PresentInferenceResult(
     hal_platform &platform,
     const std::vector<arm::app::ClassificationResult> &results)
 {
@@ -93,19 +85,6 @@ bool image::PresentInferenceResult(
     return true;
 }
 
-void image::RgbToGrayscale(const uint8_t *srcPtr, uint8_t *dstPtr, const size_t dstImgSz)
-{
-    float R=0.299;
-    float G=0.587;
-    float B=0.114;
-    for (size_t i = 0; i < dstImgSz; ++i, srcPtr += 3) {
-        uint32_t  int_gray = R * (*srcPtr) +
-                             G * (*(srcPtr + 1)) +
-                             B * (*(srcPtr + 2));
-        *dstPtr++ = int_gray <= std::numeric_limits<uint8_t>::max() ?
-                        int_gray : std::numeric_limits<uint8_t>::max();
-    }
-}
 
 void IncrementAppCtxIfmIdx(arm::app::ApplicationContext& ctx, const std::string& useCase)
 {
diff --git a/source/application/main/include/ImageUtils.hpp b/source/application/main/include/ImageUtils.hpp
new file mode 100644
index 0000000..a8c7650
--- /dev/null
+++ b/source/application/main/include/ImageUtils.hpp
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2022 Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef IMAGE_UTILS_HPP
+#define IMAGE_UTILS_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <forward_list>
+#include <vector>
+
+/* Helper macro to convert RGB888 to RGB565 format. */
+#define RGB888_TO_RGB565(R8,G8,B8)  ((((R8>>3) & 0x1F) << 11) |     \
+                                     (((G8>>2) & 0x3F) << 5)  |     \
+                                     ((B8>>3) & 0x1F))
+
+constexpr uint16_t COLOR_BLACK  = 0;
+constexpr uint16_t COLOR_GREEN  = RGB888_TO_RGB565(  0, 255,  0); // 2016;
+constexpr uint16_t COLOR_YELLOW = RGB888_TO_RGB565(255, 255,  0); // 65504;
+
+
+namespace arm {
+namespace app {
+namespace image {
+
+    /**
+     * Contains the x,y co-ordinates of a box centre along with the box width and height.
+     */
+    struct Box {
+        float x;
+        float y;
+        float w;
+        float h;
+    };
+
+    struct Detection {
+        Box bbox;
+        std::vector<float> prob;
+        float objectness;
+    };
+
+    /**
+     * @brief       Calculate the 1D overlap.
+     * @param[in]   x1Center   First center point.
+     * @param[in]   width1     First width.
+     * @param[in]   x2Center   Second center point.
+     * @param[in]   width2     Second width.
+     * @return      The overlap between the two lines.
+     **/
+    float Calculate1DOverlap(float x1Center, float width1, float x2Center, float width2);
+
+    /**
+     * @brief       Calculate the intersection between the two given boxes.
+     * @param[in]   box1   First box.
+     * @param[in]   box2   Second box.
+     * @return      The intersection value.
+     **/
+    float CalculateBoxIntersect(Box& box1, Box& box2);
+
+    /**
+     * @brief       Calculate the union between the two given boxes.
+     * @param[in]   box1   First box.
+     * @param[in]   box2   Second box.
+     * @return      The two given boxes union value.
+     **/
+    float CalculateBoxUnion(Box& box1, Box& box2);
+
+    /**
+     * @brief       Calculate the intersection over union between the two given boxes.
+     * @param[in]   box1   First box.
+     * @param[in]   box2   Second box.
+     * @return      The intersection over union value.
+     **/
+    float CalculateBoxIOU(Box& box1, Box& box2);
+
+    /**
+     * @brief       Calculate the Non-Maxima suppression on the given detection boxes.
+     * @param[in]   detections    List of Detection boxes.
+     * @param[in]   classes       Number of classes.
+     * @param[in]   iouThreshold  Intersection over union threshold.
+     **/
+    void CalculateNMS(std::forward_list<Detection>& detections, int classes, float iouThreshold);
+
+    /**
+     * @brief           Helper function to convert a UINT8 image to INT8 format.
+     * @param[in,out]   data            Pointer to the data start.
+     * @param[in]       kMaxImageSize   Total number of pixels in the image.
+     **/
+    void ConvertImgToInt8(void* data, size_t kMaxImageSize);
+
+    /**
+     * @brief       Converts RGB image to grayscale.
+     * @param[in]   srcPtr   Pointer to RGB source image.
+     * @param[out]  dstPtr   Pointer to grayscale destination image.
+     * @param[in]   imgSz    Destination image size.
+     **/
+    void RgbToGrayscale(const uint8_t* srcPtr, uint8_t* dstPtr, size_t dstImgSz);
+
+} /* namespace image */
+} /* namespace app */
+} /* namespace arm */
+
+#endif /* IMAGE_UTILS_HPP */
\ No newline at end of file
diff --git a/source/application/main/include/UseCaseCommonUtils.hpp b/source/application/main/include/UseCaseCommonUtils.hpp
index cd0cb69..7f5dde6 100644
--- a/source/application/main/include/UseCaseCommonUtils.hpp
+++ b/source/application/main/include/UseCaseCommonUtils.hpp
@@ -24,30 +24,10 @@
 #include "UseCaseHandler.hpp"       /* Handlers for different user options. */
 #include "Classifier.hpp"           /* Classifier. */
 #include "InputFiles.hpp"
-#include <cinttypes>
-
-
-/* Helper macro to convert RGB888 to RGB565 format. */
-#define RGB888_TO_RGB565(R8,G8,B8)  ((((R8>>3) & 0x1F) << 11) |     \
-                                     (((G8>>2) & 0x3F) << 5)  |     \
-                                     ((B8>>3) & 0x1F))
-
-constexpr uint16_t COLOR_BLACK  = 0;
-constexpr uint16_t COLOR_GREEN  = RGB888_TO_RGB565(  0u, 255u,  0u); // 2016;
-constexpr uint16_t COLOR_YELLOW = RGB888_TO_RGB565(255u, 255u,  0u); // 65504;
 
 
 void DisplayCommonMenu();
 
-namespace image{
-
-  /**
-  * @brief           Helper function to convert a UINT8 image to INT8 format.
-  * @param[in,out]   data            Pointer to the data start.
-  * @param[in]       kMaxImageSize   Total number of pixels in the image.
-  **/
-  void ConvertImgToInt8(void * data, size_t kMaxImageSize);
-
   /**
    * @brief           Presents inference results using the data presentation
    *                  object.
@@ -55,17 +35,9 @@ namespace image{
    * @param[in]       results     Vector of classification results to be displayed.
    * @return          true if successful, false otherwise.
    **/
-  bool PresentInferenceResult(hal_platform & platform,
-    const std::vector < arm::app::ClassificationResult > & results);
+bool PresentInferenceResult(hal_platform& platform,
+                            const std::vector<arm::app::ClassificationResult>& results);
 
-  /**
-   * @brief       Converts RGB image to grayscale.
-   * @param[in]   srcPtr   Pointer to RGB source image.
-   * @param[out]  dstPtr   Pointer to grayscale destination image.
-   * @param[in]   imgSz    Destination image size.
-   **/
-  void RgbToGrayscale(const uint8_t *srcPtr, uint8_t *dstPtr, const size_t dstImgSz);
-}
 
 /**
    * @brief           Helper function to increment current input feature vector index.