COMPMID-578: Implement FAST corners for CL/NEON

Change-Id: Ifa74e2bf05546de9a49aa185e22fba50438d8ad6
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/113946
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Pablo Tello <pablo.tello@arm.com>

1 files changed, 252 insertions, 0 deletions

diff --git a/tests/validation/reference/FastCorners.cpp b/tests/validation/reference/FastCorners.cpp
new file mode 100644
index 0000000000..ae70e365c3
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+++ b/tests/validation/reference/FastCorners.cpp
@@ -0,0 +1,252 @@
+/*
+ * Copyright (c) 2017-2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include "FastCorners.h"
+
+#include "Utils.h"
+#include "tests/validation/Helpers.h"
+#include "tests/validation/reference/NonMaximaSuppression.h"
+
+#include "tests/framework/Asserts.h"
+#include <iomanip>
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+namespace reference
+{
+namespace
+{
+constexpr unsigned int bresenham_radius = 3;
+constexpr unsigned int bresenham_count  = 16;
+
+/*
+    Offsets of the 16 pixels in the Bresenham circle of radius 3 centered on P
+        . . . . . . . . .
+        . . . F 0 1 . . .
+        . . E . . . 2 . .
+        . D . . . . . 3 .
+        . C . . P . . 4 .
+        . B . . . . . 5 .
+        . . A . . . 6 . .
+        . . . 9 8 7 . . .
+        . . . . . . . . .
+*/
+const std::array<std::array<int, 2>, 16> circle_offsets =
+{
+    {
+        { { 0, -3 } },  // 0 - pixel #1
+        { { 1, -3 } },  // 1 - pixel #2
+        { { 2, -2 } },  // 2 - pixel #3
+        { { 3, -1 } },  // 3 - pixel #4
+        { { 3, 0 } },   // 4 - pixel #5
+        { { 3, 1 } },   // 5 - pixel #6
+        { { 2, 2 } },   // 6 - pixel #7
+        { { 1, 3 } },   // 7 - pixel #8
+        { { 0, 3 } },   // 8 - pixel #9
+        { { -1, 3 } },  // 9 - pixel #10
+        { { -2, 2 } },  // A - pixel #11
+        { { -3, 1 } },  // B - pixel #12
+        { { -3, 0 } },  // C - pixel #13
+        { { -3, -1 } }, // D - pixel #14
+        { { -2, -2 } }, // E - pixel #15
+        { { -1, -3 } }  // F - pixel #16
+    }
+};
+
+/*
+    FAST-9 bit masks for consecutive points surrounding a corner candidate
+
+    // Speed-up rejection of non-corners by checking pixels 1, 9, then 5, 13...
+    const std::array<unsigned int, 16> fast9_order = { { 0, 8, 4, 12, 1, 2, 3, 5, 6, 7, 9, 10, 11, 13, 14, 15 } };
+*/
+const std::array<uint16_t, 16> fast9_masks =
+{
+    {
+        0x01FF, // 0000 0001 1111 1111
+        0x03FE, // 0000 0011 1111 1110
+        0x07FC, // 0000 0111 1111 1100
+        0x0FF8, // 0000 1111 1111 1000
+        0x1FF0, // 0001 1111 1111 0000
+        0x3FE0, // 0011 1111 1110 0000
+        0x7FC0, // 0111 1111 1100 0000
+        0xFF80, // 1111 1111 1000 0000
+        0xFF01, // 1111 1111 0000 0001
+        0xFE03, // 1111 1110 0000 0011
+        0xFC07, // 1111 1100 0000 0111
+        0xF80F, // 1111 1000 0000 1111
+        0xF01F, // 1111 0000 0001 1111
+        0xE03F, // 1110 0000 0011 1111
+        0xC07F, // 1100 0000 0111 1111
+        0x80FF  // 1000 0000 1111 1111
+    }
+};
+
+inline bool in_range(const uint8_t low, const uint8_t high, const uint8_t val)
+{
+    return low <= val && val <= high;
+}
+
+template <typename T, typename F>
+bool is_a_corner(const Coordinates &candidate, const SimpleTensor<T> &src, uint8_t threshold, BorderMode border_mode, T constant_border_value, F intensity_at)
+{
+    const auto intensity_p   = tensor_elem_at(src, candidate, border_mode, constant_border_value);
+    const auto thresh_bright = intensity_p + threshold;
+    const auto thresh_dark   = intensity_p - threshold;
+
+    // Quicker rejection of non-corner points by checking pixels 1, 9 then 5, 13 around the candidate
+    const auto p1  = intensity_at(candidate, 0);
+    const auto p9  = intensity_at(candidate, 8);
+    const auto p5  = intensity_at(candidate, 4);
+    const auto p13 = intensity_at(candidate, 12);
+
+    if((in_range(thresh_dark, thresh_bright, p1) && in_range(thresh_dark, thresh_bright, p9))
+       || (in_range(thresh_dark, thresh_bright, p5) && in_range(thresh_dark, thresh_bright, p13)))
+    {
+        return false;
+    }
+
+    uint16_t mask_bright = 0;
+    uint16_t mask_dark   = 0;
+
+    // Set bits of the brighter/darker pixels mask accordingly
+    for(unsigned int n = 0; n < bresenham_count; ++n)
+    {
+        T intensity_n = intensity_at(candidate, n);
+        mask_bright |= (intensity_n > thresh_bright) << n;
+        mask_dark |= (intensity_n < thresh_dark) << n;
+    }
+
+    // Mark as corner candidate if brighter/darker pixel sequence satisfies any one of the FAST-9 masks
+    const auto found = std::find_if(fast9_masks.begin(), fast9_masks.end(), [&](decltype(fast9_masks[0]) mask)
+    {
+        return (mask_bright & mask) == mask || (mask_dark & mask) == mask;
+    });
+
+    return found != fast9_masks.end();
+}
+} // namespace
+
+template <typename T>
+std::vector<KeyPoint> fast_corners(const SimpleTensor<T> &src, float input_thresh, bool suppress_nonmax, BorderMode border_mode, T constant_border_value)
+{
+    // Get intensity of pixel at given index on the Bresenham circle around a candidate point
+    const auto intensity_at = [&](const Coordinates & point, const unsigned int idx)
+    {
+        const auto  offs = circle_offsets[idx];
+        Coordinates px{ point.x() + offs[0], point.y() + offs[1] };
+        return tensor_elem_at(src, px, border_mode, constant_border_value);
+    };
+
+    const auto            threshold = static_cast<uint8_t>(input_thresh);
+    std::vector<KeyPoint> corners;
+
+    // 1. Detect potential corners (the segment test)
+    std::vector<Coordinates> corner_candidates;
+    SimpleTensor<float>      scores(src.shape(), DataType::F32);
+    ValidRegion              valid_region = shape_to_valid_region(src.shape(), BorderMode::UNDEFINED == border_mode, BorderSize(bresenham_radius));
+
+    for(int i = 0; i < src.num_elements(); ++i)
+    {
+        Coordinates candidate = index2coord(src.shape(), i);
+        scores[i]             = 0.f;
+        if(!is_in_valid_region(valid_region, candidate))
+        {
+            continue;
+        }
+
+        if(is_a_corner(candidate, src, threshold, border_mode, constant_border_value, intensity_at))
+        {
+            corner_candidates.emplace_back(candidate);
+            scores[i] = 1.f;
+        }
+    }
+
+    // 2. Calculate corner scores if non-maxima suppression
+    // The corner response Cp function is defined as the largest threshold t for which the pixel p remains a corner
+    if(suppress_nonmax)
+    {
+        for(const auto &candidate : corner_candidates)
+        {
+            const auto index = coord2index(scores.shape(), candidate);
+
+#ifdef CALC_CORNER_RESPONSE_BY_ITERATION
+            auto response = threshold;
+            while(is_a_corner(candidate, src, response, border_mode, constant_border_value, intensity_at))
+            {
+                response += 1;
+            }
+            scores[index] = response - 1;
+#else  // CALC_CORNER_RESPONSE_BY_ITERATION
+            uint8_t thresh_max = UINT8_MAX;
+            uint8_t thresh_min = threshold;
+            uint8_t response   = (thresh_min + thresh_max) / 2;
+
+            while(thresh_max - thresh_min > 1)
+            {
+                response = (thresh_min + thresh_max) / 2;
+                if(is_a_corner(candidate, src, response, border_mode, constant_border_value, intensity_at))
+                {
+                    thresh_min = response; // raise threshold
+                }
+                else
+                {
+                    thresh_max = response; // lower threshold
+                }
+            }
+            scores[index] = thresh_min;
+#endif // CALC_CORNER_RESPONSE_BY_ITERATION
+        }
+
+        scores       = non_maxima_suppression(scores, border_mode, static_cast<float>(constant_border_value));
+        valid_region = shape_to_valid_region(scores.shape(), BorderMode::UNDEFINED == border_mode, BorderSize(bresenham_radius + 1));
+    }
+
+    for(const auto &candidate : corner_candidates)
+    {
+        const auto index = coord2index(scores.shape(), candidate);
+        if(scores[index] > 0.f && is_in_valid_region(valid_region, candidate))
+        {
+            KeyPoint corner;
+            corner.x               = candidate.x();
+            corner.y               = candidate.y();
+            corner.strength        = scores[index];
+            corner.tracking_status = 1;
+            corner.scale           = 0.f;
+            corner.orientation     = 0.f;
+            corner.error           = 0.f;
+            corners.emplace_back(corner);
+        }
+    }
+
+    return corners;
+}
+
+template std::vector<KeyPoint> fast_corners(const SimpleTensor<uint8_t> &src, float threshold, bool suppress_nonmax, BorderMode border_mode, uint8_t constant_border_value);
+} // namespace reference
+} // namespace validation
+} // namespace test
+} // namespace arm_compute