| /* |
| * 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 |
| Rejection of non-corners is expedited by checking pixels 1, 9, then 5, 13... |
| */ |
| 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 offset = circle_offsets[idx]; |
| Coordinates px{ point.x() + offset[0], point.y() + offset[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<uint8_t> scores(src.shape(), DataType::U8); |
| 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; |
| 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; |
| } |
| } |
| |
| // 2. Calculate corner scores if necessary |
| if(suppress_nonmax) |
| { |
| for(const auto &candidate : corner_candidates) |
| { |
| const auto index = coord2index(scores.shape(), candidate); |
| uint8_t thresh_max = UINT8_MAX; |
| uint8_t thresh_min = threshold; |
| uint8_t response = (thresh_min + thresh_max) / 2; |
| |
| // Corner score (response) is the largest threshold for which the pixel remains a corner |
| 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; |
| } |
| |
| scores = non_maxima_suppression(scores, border_mode, 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 |