| /* |
| * Copyright (c) 2016-2019 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 "arm_compute/core/NEON/kernels/NEFastCornersKernel.h" |
| |
| #include "arm_compute/core/Coordinates.h" |
| #include "arm_compute/core/Error.h" |
| #include "arm_compute/core/Helpers.h" |
| #include "arm_compute/core/Validate.h" |
| |
| #include <algorithm> |
| #include <arm_neon.h> |
| #include <cstddef> |
| #include <limits> |
| |
| using namespace arm_compute; |
| |
| NEFastCornersKernel::NEFastCornersKernel() |
| : INEKernel(), _input(nullptr), _output(nullptr), _threshold(0), _non_max_suppression(false) |
| { |
| } |
| |
| namespace |
| { |
| constexpr size_t PERMUTATIONS = 16; |
| constexpr size_t PERM_SIZE = 16; |
| |
| inline uint8x8x2_t create_permutation_index(size_t k) |
| { |
| ARM_COMPUTE_ERROR_ON(k >= PERMUTATIONS); |
| |
| static const std::array<std::array<uint8_t, PERMUTATIONS>, PERM_SIZE> permutations_table{ { { 0, 1, 2, 3, 4, 5, 6, 7, 8, 255, 255, 255, 255, 255, 255, 255 }, |
| { 15, 0, 1, 2, 3, 4, 5, 6, 7, 255, 255, 255, 255, 255, 255, 255 }, |
| { 14, 15, 0, 1, 2, 3, 4, 5, 6, 255, 255, 255, 255, 255, 255, 255 }, |
| { 13, 14, 15, 0, 1, 2, 3, 4, 5, 255, 255, 255, 255, 255, 255, 255 }, |
| { 12, 13, 14, 15, 0, 1, 2, 3, 4, 255, 255, 255, 255, 255, 255, 255 }, |
| { 11, 12, 13, 14, 15, 0, 1, 2, 3, 255, 255, 255, 255, 255, 255, 255 }, |
| { 10, 11, 12, 13, 14, 15, 0, 1, 2, 255, 255, 255, 255, 255, 255, 255 }, |
| { 9, 10, 11, 12, 13, 14, 15, 0, 1, 255, 255, 255, 255, 255, 255, 255 }, |
| { 8, 9, 10, 11, 12, 13, 14, 15, 0, 255, 255, 255, 255, 255, 255, 255 }, |
| { 7, 8, 9, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255 }, |
| { 6, 7, 8, 9, 10, 11, 12, 13, 14, 255, 255, 255, 255, 255, 255, 255 }, |
| { 5, 6, 7, 8, 9, 10, 11, 12, 13, 255, 255, 255, 255, 255, 255, 255 }, |
| { 4, 5, 6, 7, 8, 9, 10, 11, 12, 255, 255, 255, 255, 255, 255, 255 }, |
| { 3, 4, 5, 6, 7, 8, 9, 10, 11, 255, 255, 255, 255, 255, 255, 255 }, |
| { 2, 3, 4, 5, 6, 7, 8, 9, 10, 255, 255, 255, 255, 255, 255, 255 }, |
| { 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255, 255 } |
| |
| } }; |
| |
| const uint8x8x2_t index = |
| { |
| { |
| vld1_u8(permutations_table[k].data()), |
| vld1_u8(permutations_table[k].data() + 8) |
| } |
| }; |
| |
| return index; |
| } |
| |
| inline uint8x8x4_t create_circle_index_register() |
| { |
| /* |
| This function creates the index registers to retrieve the 16 texels in the Bresenham circle of radius 3 with center in P. |
| |
| . . F 0 1 . . . |
| . E . . . 2 . . |
| D . . . . . 3 . |
| C . . P . . 4 . |
| B . . . . . 5 . |
| . A . . . 6 . . |
| . . 9 8 7 . . . |
| |
| Where . is an irrelevant texel value |
| |
| We want to retrieve all texels [0,F] |
| |
| The 4 registers in r will then be used to get these texels out of two tables in the function get_circle_texels() |
| |
| The first table holds the top 4 rows of texels |
| . . F 0 1 . . . |
| . E . . . 2 . . |
| D . . . . . 3 . |
| C . . P . . 4 . |
| |
| The second table the bottom 3 rows of texels |
| B . . . . . 5 . |
| . A . . . 6 . . |
| . . 9 8 7 . . . |
| |
| */ |
| static const std::array<uint8_t, 8> top_right = |
| { |
| /* The register r.val[0] will be used to retrieve these texels: |
| . . . 0 1 . . . |
| . . . . . 2 . . |
| . . . . . . 3 . |
| . . . . . . 4 . |
| */ |
| 3 /* top table, first row, elem 4, value 0 in the diagram above */, |
| 4 /* top table, first row, elem 5, value 1 in the diagram above */, |
| 13 /* top table, second row, elem 6, value 2 in the diagram above */, |
| 22 /* top table, third row, elem 7, value 3 in the diagram above*/, |
| 30 /* top table, fourth row, elem 7, value 4 in the diagram above*/, |
| 255, |
| 255, |
| 255 |
| }; |
| |
| static const std::array<uint8_t, 8> bottom_right = |
| { |
| /* The register r.val[1] will be used to retrieve these texels: |
| . . . . . . 5 . |
| . . . . . 6 . . |
| . . . . 7 . . . |
| */ |
| 255, |
| 255, |
| 255, |
| 255, |
| 255, |
| 6 /* low table, first row, elem 7, value 5 in the diagram above*/, |
| 13 /* low table, second row, elem 6, value 6 in the diagram above*/, |
| 20 /* low table, third row, elem 5, value 7 in the diagram above*/ |
| }; |
| |
| static const std::array<uint8_t, 8> top_left = |
| { |
| /* The register r.val[2] will be used to retrieve these texels: |
| . . F . . . . . |
| . E . . . . . . |
| D . . . . . . . |
| C . . . . . . . |
| */ |
| 255, |
| 255, |
| 255, |
| 255, |
| 24 /* top table, fourth row, elem 1, value C in the diagram above */, |
| 16 /* top table, third row, elem 1, value D in the diagram above*/, |
| 9 /* top table, second row, elem 2, value E in the diagram above*/, |
| 2 /* top table, first row, elem 3, value F in the diagram above*/ |
| }; |
| |
| static const std::array<uint8_t, 8> bottom_left = |
| { |
| /* The register r.val[3] will be used to retrieve these texels: |
| B . . . . . . . |
| . A . . . . . . |
| . . 9 8 . . . . |
| */ |
| 19 /* low table, third row, elem 4, value 8 in the diagram above */, |
| 18 /* low table, third row, elem 3, value 9 in the diagram above */, |
| 9 /* low table, second row, elem 2, value A in the diagram above */, |
| 0 /* low table, first row, elem 1, value B in the diagram above */, |
| 255, |
| 255, |
| 255, |
| 255 |
| }; |
| |
| const uint8x8x4_t reg = |
| { |
| { |
| vld1_u8(top_right.data()), |
| vld1_u8(bottom_right.data()), |
| vld1_u8(top_left.data()), |
| vld1_u8(bottom_left.data()) |
| } |
| }; |
| |
| return reg; |
| } |
| |
| inline uint8x16_t get_circle_texels(const uint8x8x4_t &index, const uint8x8x4_t &tbl_hi, const uint8x8x3_t &tbl_lo) |
| { |
| /* |
| This function loads the 16 texels in the Bresenham circle of radius 3 into the register 'texels'. |
| The parameter 'index' is an array of indices which was previously setup in setup_circle_index_register(). |
| tbl_hi and tbl_lo are the two tables holding the texels in the window [(-3,-3),(+3,+3)] for a given texel P |
| */ |
| return vcombine_u8(vtbx3_u8(vtbl4_u8(tbl_hi, index.val[0]), tbl_lo, index.val[1]), |
| vtbx3_u8(vtbl4_u8(tbl_hi, index.val[2]), tbl_lo, index.val[3])); |
| } |
| |
| inline uint8x16_t get_permutation_texels(const uint8x8x2_t &permutation_index, const uint8x8x2_t &tbl_circle) |
| { |
| /* |
| This function stores the 9 texels of a give permutation X in the neon register 'texels' |
| |
| 'tbl_circle' is a LUT with the texels 0 to F |
| |
| . . F 0 1 . . . |
| . E . . . 2 . . |
| D . . . . . 3 . |
| C . . P . . 4 . |
| B . . . . . 5 . |
| . A . . . 6 . . |
| . . 9 8 7 . . . |
| |
| 'permutation_index' is one of the permutations below: |
| |
| { 0, 1, 2, 3, 4, 5, 6, 7, 8}, |
| { F, 0, 1, 2, 3, 4, 5, 6, 7}, |
| { E, F, 0, 1, 2, 3, 4, 5, 6}, |
| { D, E, F, 0, 1, 2, 3, 4, 5}, |
| { C, D, E, F, 0, 1, 2, 3, 4}, |
| { B, C, D, E, F, 0, 1, 2, 3}, |
| { A, B, C, D, E, F, 0, 1, 2}, |
| { 9, A, B, C, D, E, F, 0, 1}, |
| { 8, 9, A, B, C, D, E, F, 0}, |
| { 7, 8, 9, A, B, C, D, E, F}, |
| { 6, 7, 8, 9, A, B, C, D, E}, |
| { 5, 6, 7, 8, 9, A, B, C, D}, |
| { 4, 5, 6, 7, 8, 9, A, B, C}, |
| { 3, 4, 5, 6, 7, 8, 9, A, B}, |
| { 2, 3, 4, 5, 6, 7, 8, 9, A}, |
| { 1, 2, 3, 4, 5, 6, 7, 8, 9}, |
| */ |
| static const uint8x8_t perm_right = vdup_n_u8(255); // init to 255 so that vtbx preserves the original values of the lanes |
| |
| return vcombine_u8(vtbl2_u8(tbl_circle, permutation_index.val[0]), |
| vtbx2_u8(perm_right, tbl_circle, permutation_index.val[1])); |
| } |
| |
| inline bool is_permutation_brighter(const uint8x16_t &permutation, const uint8x16_t &pg) |
| { |
| const uint8x16_t res_gt = vcgtq_u8(permutation, pg); |
| |
| return vget_lane_u64(vreinterpret_u64_u8(vand_u8(vget_high_u8(res_gt), vget_low_u8(res_gt))), 0) == std::numeric_limits<uint64_t>::max(); |
| } |
| |
| inline bool is_permutation_darker(const uint8x16_t &permutation, const uint8x16_t &pl) |
| { |
| const uint8x16_t res_lt = vcltq_u8(permutation, pl); |
| const uint64x2_t u64res_lt = vreinterpretq_u64_u8(res_lt); |
| const uint64_t t3 = vgetq_lane_u64(u64res_lt, 0); |
| const uint64_t t4 = vgetq_lane_u64(u64res_lt, 1); |
| |
| return std::numeric_limits<uint64_t>::max() == t3 && 255 == t4; |
| } |
| |
| inline bool is_permutation_corner(const uint8x16_t &permutation, const uint8x16_t &pg, const uint8x16_t &pl) |
| { |
| return is_permutation_brighter(permutation, pg) || is_permutation_darker(permutation, pl); |
| } |
| |
| inline bool point_is_fast_corner(uint8_t p, uint8_t threshold, const uint8x8x2_t &tbl_circle_texels, std::array<uint8x8x2_t, PERMUTATIONS> &perm_indices) |
| { |
| /* |
| This function determines whether the point 'p' is a corner. |
| */ |
| uint8x16_t pg = vqaddq_u8(vdupq_n_u8(p), vdupq_n_u8(threshold)); |
| uint8x16_t pl = vqsubq_u8(vdupq_n_u8(p), vdupq_n_u8(threshold)); |
| |
| bool corner_detected = false; |
| |
| for(size_t j = 0; !corner_detected && j < PERMUTATIONS; ++j) |
| { |
| const uint8x16_t pe_texels = get_permutation_texels(perm_indices[j], tbl_circle_texels); |
| corner_detected = is_permutation_corner(pe_texels, pg, pl); |
| } |
| |
| return corner_detected; |
| } |
| |
| inline uint8x8x2_t create_circle_tbl(const std::array<uint8_t *const __restrict, 7> &buffer, size_t in_offset, const uint8x8x4_t &circle_index_r) |
| { |
| /* |
| This function builds a LUT holding the 16 texels in the Brensenham circle radius 3. |
| circle_index_r is a vector of 4 registers to retrieve the texels from the two tables mentioned above. |
| */ |
| |
| //Load the texels in the window [(x-3,y-3),(x+3,y+3)]. |
| //The top 4 rows are loaded in tbl_hi and the low 3 rows in tbl_lo. |
| //These two tables are then used to retrieve the texels in the Bresenham circle of radius 3. |
| const uint8x8x4_t tbl_window_hi = |
| { |
| { |
| vld1_u8(buffer[0] + in_offset), |
| vld1_u8(buffer[1] + in_offset), |
| vld1_u8(buffer[2] + in_offset), |
| vld1_u8(buffer[3] + in_offset) |
| } |
| }; |
| |
| const uint8x8x3_t tbl_window_lo = |
| { |
| { |
| vld1_u8(buffer[4] + in_offset), |
| vld1_u8(buffer[5] + in_offset), |
| vld1_u8(buffer[6] + in_offset) |
| } |
| }; |
| |
| const uint8x16_t circle_texels = get_circle_texels(circle_index_r, tbl_window_hi, tbl_window_lo); |
| |
| const uint8x8x2_t tbl_circle_texels = |
| { |
| { |
| vget_low_u8(circle_texels), |
| vget_high_u8(circle_texels) |
| } |
| }; |
| |
| return tbl_circle_texels; |
| } |
| |
| inline uint8_t get_point_score(uint8_t p, uint8_t tolerance, const uint8x8x2_t &tbl_circle, std::array<uint8x8x2_t, PERMUTATIONS> &perm_indices) |
| { |
| uint8_t b = 255; |
| uint8_t a = tolerance; |
| |
| while(b - a > 1) |
| { |
| const uint16_t ab = a + b; |
| const uint8_t c = ab >> 1; |
| |
| if(point_is_fast_corner(p, c, tbl_circle, perm_indices)) |
| { |
| a = c; |
| } |
| else |
| { |
| b = c; |
| } |
| } |
| |
| return a; |
| } |
| } // namespace |
| |
| BorderSize NEFastCornersKernel::border_size() const |
| { |
| return BorderSize(3); |
| } |
| |
| void NEFastCornersKernel::configure(const IImage *input, IImage *output, uint8_t threshold, bool non_max_suppression, bool border_undefined) |
| { |
| ARM_COMPUTE_ERROR_ON_TENSOR_NOT_2D(input); |
| ARM_COMPUTE_ERROR_ON_TENSOR_NOT_2D(output); |
| ARM_COMPUTE_ERROR_ON_DATA_TYPE_CHANNEL_NOT_IN(input, 1, DataType::U8); |
| ARM_COMPUTE_ERROR_ON_DATA_TYPE_CHANNEL_NOT_IN(output, 1, DataType::U8); |
| ARM_COMPUTE_ERROR_ON_MSG(border_undefined == false, "Not implemented"); |
| |
| _input = input; |
| _output = output; |
| _threshold = threshold; |
| _non_max_suppression = non_max_suppression; |
| |
| constexpr unsigned int num_elems_processed_per_iteration = 1; |
| constexpr unsigned int num_elems_read_per_iteration = 8; |
| constexpr unsigned int num_elems_written_per_iteration = 1; |
| constexpr unsigned int num_rows_read_per_iteration = 7; |
| |
| // Configure kernel window |
| Window win = calculate_max_window(*input->info(), Steps(num_elems_processed_per_iteration), border_undefined, border_size()); |
| AccessWindowHorizontal output_access(output->info(), 0, num_elems_written_per_iteration); |
| AccessWindowRectangle input_access(input->info(), -border_size().left, -border_size().top, num_elems_read_per_iteration, num_rows_read_per_iteration); |
| |
| update_window_and_padding(win, input_access, output_access); |
| |
| output_access.set_valid_region(win, input->info()->valid_region(), border_undefined, border_size()); |
| |
| INEKernel::configure(win); |
| } |
| |
| void NEFastCornersKernel::run(const Window &window, const ThreadInfo &info) |
| { |
| ARM_COMPUTE_UNUSED(info); |
| ARM_COMPUTE_ERROR_ON_UNCONFIGURED_KERNEL(this); |
| ARM_COMPUTE_ERROR_ON_INVALID_SUBWINDOW(INEKernel::window(), window); |
| |
| std::array<uint8x8x2_t, PERMUTATIONS> perm_index{ {} }; |
| /* |
| We use a LUT loaded with 7 rows of uint8_t from the input image [-3,-3]...[+3,+3] to retrieve the texels in the Brensenham circle radius 3 and put them in one neon register uint8x16_t. |
| The three lines below setup the neon index registers to get these texels out from the table |
| */ |
| const uint8x8x4_t circle_index_r = create_circle_index_register(); |
| /* |
| We put the 16 texels (circle) in a LUT to easily generate all the permutations. The for block below setups the indices for each permutation. |
| */ |
| for(size_t k = 0; k < PERMUTATIONS; ++k) |
| { |
| perm_index[k] = create_permutation_index(k); |
| } |
| |
| Iterator in(_input, window); |
| Iterator out(_output, window); |
| |
| const std::array<uint8_t *const __restrict, 7> in_row |
| { |
| _input->ptr_to_element(Coordinates(-3, -3)), |
| _input->ptr_to_element(Coordinates(-3, -2)), |
| _input->ptr_to_element(Coordinates(-3, -1)), |
| _input->ptr_to_element(Coordinates(-3, 0)), |
| _input->ptr_to_element(Coordinates(-3, 1)), |
| _input->ptr_to_element(Coordinates(-3, 2)), |
| _input->ptr_to_element(Coordinates(-3, 3)) |
| }; |
| |
| auto is_rejected = [](uint8_t p, uint8_t q, uint8_t a, uint8_t b) |
| { |
| const bool p_is_in_ab = (a <= p) && (p <= b); |
| const bool q_is_in_ab = (a <= q) && (q <= b); |
| return p_is_in_ab && q_is_in_ab; |
| }; |
| |
| execute_window_loop(window, [&](const Coordinates &) |
| { |
| const size_t in_offset = in.offset(); |
| const uint8_t p0 = *in.ptr(); |
| const uint8_t b = std::min(p0 + _threshold, 255); |
| const uint8_t a = std::max(p0 - _threshold, 0); |
| uint8_t score = 0; |
| /* |
| Fast check to discard points which cannot be corners and avoid the expensive computation of the potential 16 permutations |
| |
| pixels 1 and 9 are examined, if both I1 and I9 are within [Ip - t, Ip + t], then candidate p is not a corner. |
| */ |
| const uint8_t p1 = (in_offset + in_row[0])[3]; |
| const uint8_t p9 = (in_offset + in_row[6])[3]; |
| |
| if(!is_rejected(p1, p9, a, b)) |
| { |
| /* pixels 5 and 13 are further examined to check whether three of them are brighter than Ip + t or darker than Ip - t */ |
| const uint8_t p5 = (in_offset + in_row[3])[6]; |
| const uint8_t p13 = (in_offset + in_row[3])[0]; |
| |
| if(!is_rejected(p5, p13, a, b)) |
| { |
| /* at this stage we use the full test with the 16 permutations to classify the point as corner or not */ |
| const uint8x8x2_t tbl_circle_texel = create_circle_tbl(in_row, in_offset, circle_index_r); |
| |
| if(point_is_fast_corner(p0, _threshold, tbl_circle_texel, perm_index)) |
| { |
| if(_non_max_suppression) |
| { |
| score = get_point_score(p0, _threshold, tbl_circle_texel, perm_index); |
| } |
| else |
| { |
| score = 1; |
| } |
| } |
| } |
| } |
| |
| *out.ptr() = score; |
| }, |
| in, out); |
| } |