Simplify pregrader

This merge request processes the SIG feedback related to fix_corner_markers()

tests/test_images.py

+import cv2
+import os
+import numpy as np
+import pytest
+
+from zesje.images import get_delta, get_corner_marker_sides, fix_corner_markers, add_tup, sub_tup
+from zesje.scans import find_corner_marker_keypoints
+
+
+@pytest.mark.parametrize(
+    'shape,corners,expected',
+    [((240, 200, 3), [(120, 50), (50, 200), (120, 200)], (50, 50)),
+     ((240, 200, 3), [(50, 50), (50, 200), (120, 200)], (120, 50)),
+     ((240, 200, 3), [(50, 50), (120, 50), (120, 200)], (50, 200)),
+     ((240, 200, 3), [(50, 50), (120, 50), (50, 200)], (120, 200))],
+    ids=["missing top left", "missing top right", "missing bottom left", "missing bottom right"])
+def test_three_straight_corners(shape, corners, expected):
+    corner_markers = fix_corner_markers(corners, shape)
+    assert expected in corner_markers
+
+
+def test_pdf(datadir):
+    # Max deviation of inferred corner marker and actual location
+    epsilon = 2
+
+    # Scan rotated image with 4 corner markers
+    image_filename1 = 'a4-rotated.png'
+    image_path = os.path.join(datadir, 'cornermarkers', image_filename1)
+    page_img = cv2.imread(image_path)
+
+    corners1 = find_corner_marker_keypoints(page_img)
+
+    # Scan the same image with 3 corner markers
+    image_filename2 = 'a4-rotated-3-markers.png'
+    image_path = os.path.join(datadir, 'cornermarkers', image_filename2)
+    page_img = cv2.imread(image_path)
+
+    corners2 = find_corner_marker_keypoints(page_img)
+
+    # Get marker that was removed
+    diff = [corner for corner in corners1 if corner not in corners2]
+    diff_marker = min(diff)
+
+    fixed_corners2 = fix_corner_markers(corners2, page_img.shape)
+    added_marker = [corner for corner in fixed_corners2 if corner not in corners1][0]
+
+    # Check if 'inferred' corner marker is not too far away
+    dist = np.linalg.norm(np.subtract(added_marker, diff_marker))
+
+    assert dist < epsilon
+
+
+@pytest.mark.parametrize(
+    'inputs,expected',
+    [
+        (((0, 1), (1, 1), (0, 0), None), (0, 1)),
+        (((0, 1), None, (0, 0), (0, 1)), (0, 1)),
+        (((1, 1), (2, 1), None, (2, 2)), (0, -1)),
+        ((None, (1, 1), (1, 2), (2, 2)), (-1, -1))
+    ],
+    ids=["missing bottom right", "missing top right", "missing bottom left", "missing top left"]
+)
+def test_get_delta(inputs, expected):
+    # unpack inputs so that the individual elements are paramaters
+    delta = get_delta(*inputs)
+
+    assert delta == expected
+
+
+def test_get_corner_marker_sides_all_four():
+    shape = (100, 100)
+    corner_markers = [(0, 0), (100, 0), (0, 100), (100, 100)]
+
+    assert tuple(corner_markers) == get_corner_marker_sides(corner_markers, shape)
+
+
+def test_get_corner_markers_three():
+    shape = (100, 100)
+    corner_markers = [(0, 0), (0, 100), (100, 0)]
+
+    top_left, top_right, bottom_left, bottom_right = get_corner_marker_sides(corner_markers, shape)
+
+    assert not bottom_right
+
+
+def test_add_tup():
+    tup1 = tup2 = (1, 1)
+
+    assert add_tup(tup1, tup2) == (2, 2)
+
+
+def test_sub_tup():
+    tup1 = tup2 = (1, 1)
+
+    assert sub_tup(tup1, tup2) == (0, 0)