genesys: Add utility to compute percentille of columns in image

backend/Makefile.am

@@ -516,7 +516,8 @@ libgenesys_la_SOURCES = genesys/genesys.cpp genesys/genesys.h \
     genesys/tables_motor.cpp \
     genesys/tables_motor_profile.cpp \
     genesys/tables_sensor.cpp \
-    genesys/low.cpp genesys/low.h
+    genesys/low.cpp genesys/low.h \
+    genesys/utilities.h
 
 libgenesys_la_CPPFLAGS = $(AM_CPPFLAGS) -DBACKEND_NAME=genesys
 

backend/genesys/utilities.h

@@ -0,0 +1,88 @@
+/* sane - Scanner Access Now Easy.
+
+   Copyright (C) 2019 Povilas Kanapickas <povilas@radix.lt>
+
+   This file is part of the SANE package.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+   MA 02111-1307, USA.
+
+   As a special exception, the authors of SANE give permission for
+   additional uses of the libraries contained in this release of SANE.
+
+   The exception is that, if you link a SANE library with other files
+   to produce an executable, this does not by itself cause the
+   resulting executable to be covered by the GNU General Public
+   License.  Your use of that executable is in no way restricted on
+   account of linking the SANE library code into it.
+
+   This exception does not, however, invalidate any other reasons why
+   the executable file might be covered by the GNU General Public
+   License.
+
+   If you submit changes to SANE to the maintainers to be included in
+   a subsequent release, you agree by submitting the changes that
+   those changes may be distributed with this exception intact.
+
+   If you write modifications of your own for SANE, it is your choice
+   whether to permit this exception to apply to your modifications.
+   If you do not wish that, delete this exception notice.
+*/
+
+#ifndef BACKEND_GENESYS_UTILITIES_H
+#define BACKEND_GENESYS_UTILITIES_H
+
+#include "error.h"
+#include <algorithm>
+#include <vector>
+
+namespace genesys {
+
+template<class T>
+void compute_array_percentile_approx(T* result, const T* data,
+                                     std::size_t line_count, std::size_t elements_per_line,
+                                     float percentile)
+{
+    if (line_count == 0) {
+        throw SaneException("invalid line count");
+    }
+
+    if (line_count == 1) {
+        std::copy(data, data + elements_per_line, result);
+        return;
+    }
+
+    std::vector<T> column_elems;
+    column_elems.resize(line_count, 0);
+
+    std::size_t select_elem = std::min(static_cast<std::size_t>(line_count * percentile),
+                                       line_count - 1);
+
+    auto select_it = column_elems.begin() + select_elem;
+
+    for (std::size_t ix = 0; ix < elements_per_line; ++ix) {
+        for (std::size_t iy = 0; iy < line_count; ++iy) {
+            column_elems[iy] = data[iy * elements_per_line + ix];
+        }
+
+        std::nth_element(column_elems.begin(), select_it, column_elems.end());
+
+        *result++ = *select_it;
+    }
+}
+
+} // namespace genesys
+
+#endif // BACKEND_GENESYS_UTILITIES_H

testsuite/backend/genesys/Makefile.am

@@ -24,6 +24,7 @@ genesys_tests_SOURCES = tests.cpp tests.h \
     tests_calibration.cpp \
     tests_image.cpp \
     tests_image_pipeline.cpp \
-    tests_row_buffer.cpp
+    tests_row_buffer.cpp \
+    tests_utilities.cpp
 
 genesys_tests_LDADD = $(TEST_LDADD)

testsuite/backend/genesys/tests.cpp

@@ -31,5 +31,6 @@ int main()
     genesys::test_image();
     genesys::test_image_pipeline();
     genesys::test_row_buffer();
+    genesys::test_utilities();
     return finish_tests();
 }

testsuite/backend/genesys/tests.h

@@ -29,6 +29,7 @@ void test_calibration_parsing();
 void test_image();
 void test_image_pipeline();
 void test_row_buffer();
+void test_utilities();
 
 } // namespace genesys
 

testsuite/backend/genesys/tests_utilities.cpp

@@ -0,0 +1,110 @@
+/* sane - Scanner Access Now Easy.
+
+   Copyright (C) 2019 Povilas Kanapickas <povilas@radix.lt>
+
+   This file is part of the SANE package.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+   MA 02111-1307, USA.
+*/
+
+#define DEBUG_DECLARE_ONLY
+
+#include "tests.h"
+#include "minigtest.h"
+#include "tests_printers.h"
+
+#include "../../../backend/genesys/utilities.h"
+
+namespace genesys {
+
+void test_utilities_compute_array_percentile_approx_empty()
+{
+    std::vector<std::uint16_t> data;
+    data.resize(1, 0);
+
+    ASSERT_RAISES(compute_array_percentile_approx(data.data(), data.data(), 0, 0, 0.0f),
+                  SaneException);
+}
+
+void test_utilities_compute_array_percentile_approx_single_line()
+{
+    std::vector<std::uint16_t> data = {
+        0, 1, 2, 3, 4, 5, 6, 7, 8, 9
+    };
+    std::vector<std::uint16_t> expected = data;
+    std::vector<std::uint16_t> result;
+    result.resize(data.size(), 0);
+
+    compute_array_percentile_approx(result.data(), data.data(), 1, data.size(), 0.5f);
+    ASSERT_EQ(result, expected);
+}
+
+void test_utilities_compute_array_percentile_approx_multiple_lines()
+{
+    std::vector<std::uint16_t> data = {
+         5, 17,  4, 14,  3,  9,  9,  5, 10,  1,
+         6,  1,  0, 18,  8,  5, 11, 11, 15, 12,
+         6,  8,  7,  3,  2, 15,  5, 12,  3,  3,
+         6, 12, 17,  6,  7,  7,  1,  6,  3, 18,
+        10,  5,  8,  0, 14,  3,  3,  7, 10,  5,
+        18,  7,  3, 11,  0, 14, 12, 19, 18, 11,
+         5, 16,  2,  9,  8,  2,  7,  6, 11, 18,
+        16,  5,  2,  2, 14, 18, 19, 13, 16,  1,
+         5,  9, 14,  6, 17, 16,  1,  1, 16,  0,
+        19, 18,  4, 12,  0,  7, 15,  3,  2,  6,
+    };
+    std::vector<std::uint16_t> result;
+    result.resize(10, 0);
+
+    std::vector<std::uint16_t> expected = {
+        5, 1, 0, 0, 0, 2, 1, 1, 2, 0,
+    };
+    compute_array_percentile_approx(result.data(), data.data(), 10, 10, 0.0f);
+    ASSERT_EQ(result, expected);
+
+    expected = {
+        5, 5, 2, 3, 2, 5, 3, 5, 3, 1,
+    };
+    compute_array_percentile_approx(result.data(), data.data(), 10, 10, 0.25f);
+    ASSERT_EQ(result, expected);
+
+    expected = {
+        6, 9, 4, 9, 8, 9, 9, 7, 11, 6,
+    };
+    compute_array_percentile_approx(result.data(), data.data(), 10, 10, 0.5f);
+    ASSERT_EQ(result, expected);
+
+    expected = {
+        16, 16, 8, 12, 14, 15, 12, 12, 16, 12,
+    };
+    compute_array_percentile_approx(result.data(), data.data(), 10, 10, 0.75f);
+    ASSERT_EQ(result, expected);
+
+    expected = {
+        19, 18, 17, 18, 17, 18, 19, 19, 18, 18,
+    };
+    compute_array_percentile_approx(result.data(), data.data(), 10, 10, 1.0f);
+    ASSERT_EQ(result, expected);
+}
+
+void test_utilities()
+{
+    test_utilities_compute_array_percentile_approx_empty();
+    test_utilities_compute_array_percentile_approx_single_line();
+    test_utilities_compute_array_percentile_approx_multiple_lines();
+}
+
+} // namespace genesys