Cropping investigation

tests/test_paper_ruling.py

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+import unittest
+from unittest.mock import patch
+
+import cv2
+import numpy as np
+
+from copienator.ink_detection import detect_bounds
+
+
+class PaperRulingTests(unittest.TestCase):
+    def scan(self, colour, *, warp=False):
+        image = np.full((1200, 850, 3), 255, np.uint8)
+        for y in range(20, 1200, 20):
+            cv2.line(image, (0, y), (849, y), colour, 1)
+        for x in range(10, 850, 20):
+            cv2.line(image, (x, 0), (x, 1199), colour, 1)
+        cv2.line(image, (80, 0), (80, 1199), (210, 70, 80), 2)
+        cv2.putText(image, 'answer', (120, 410), cv2.FONT_HERSHEY_SIMPLEX,
+                    1, (20, 60, 180), 2)
+        cv2.putText(image, 'more', (120, 710), cv2.FONT_HERSHEY_SIMPLEX,
+                    1, (20, 60, 180), 2)
+        if warp:
+            yy, xx = np.indices(image.shape[:2], dtype=np.float32)
+            image = cv2.remap(image, xx+2*np.sin(yy/95), yy,
+                              cv2.INTER_LINEAR, borderValue=(255,255,255))
+        return image
+
+    def test_default_path_does_not_run_experimental_colour_model(self):
+        image = self.scan((70, 110, 225))
+        with patch('copienator.ink_detection.ruling_suppression',
+                   side_effect=AssertionError('Expensive colour model invoked')):
+            result = detect_bounds(image, dpi=150)
+        self.assertLess(result['top_px'], 410)
+        self.assertGreater(result['bottom_px'], 710)
+        self.assertFalse(result.get('ruling_cleanup', False))
+
+    def test_saturated_coloured_grid_and_margin_do_not_seed_blank_edges(self):
+        for colour in [(65, 65, 65), (70, 110, 225), (155, 170, 240)]:
+            for warp in [False, True]:
+                with self.subTest(colour=colour, warp=warp):
+                    image = self.scan(colour, warp=warp)
+                    debug = {}
+                    result = detect_bounds(image, dpi=150, colour_cleanup=True, diagnostics=debug)
+                    self.assertGreater(result['top_px'], 280)
+                    self.assertLess(result['bottom_px'], 810)
+                    self.assertTrue(result['ruling_cleanup'])
+                    self.assertTrue(debug['masks']['paper_suppressed'].any())
+                    self.assertFalse(debug['masks']['foreground'][:250].any())
+
+    def test_writing_crossing_ruling_keeps_both_outer_bounds(self):
+        image = self.scan((70, 110, 225))
+        cv2.putText(image, 'top', (120, 200), cv2.FONT_HERSHEY_SIMPLEX,
+                    .7, (190, 20, 20), 2)
+        cv2.putText(image, 'bottom', (120, 1000), cv2.FONT_HERSHEY_SIMPLEX,
+                    .7, (20, 20, 20), 2)
+        result = detect_bounds(image, dpi=150, colour_cleanup=True)
+        self.assertLess(result['top_px'], 180)
+        self.assertGreater(result['bottom_px'], 1000)
+
+    def test_isolated_bars_and_axes_are_not_a_ruling_colour_family(self):
+        for colour in [(190, 20, 20), (20, 20, 20), (20, 90, 190)]:
+            with self.subTest(colour=colour):
+                image = self.scan((70, 110, 225))
+                cv2.line(image, (100, 1020), (700, 1020), colour, 3)
+                cv2.line(image, (425, 980), (425, 1120), colour, 3)
+                result = detect_bounds(image, dpi=150, colour_cleanup=True)
+                self.assertGreater(result['bottom_px'], 1120)
+
+    def test_grid_colour_with_a_thicker_answer_bar_is_preserved(self):
+        colour = (70, 110, 225)
+        image = self.scan(colour)
+        cv2.line(image, (150, 1020), (650, 1020), colour, 5)
+        self.assertGreater(detect_bounds(image, dpi=150, colour_cleanup=True)['bottom_px'], 1020)
+
+    def test_regular_fraction_bars_inside_an_answer_are_not_paper(self):
+        image = np.full((1200,850,3),255,np.uint8)
+        cv2.putText(image,'answer',(120,300),cv2.FONT_HERSHEY_SIMPLEX,
+                    1,(20,60,180),2)
+        for y in (400,550,700,850,1000):
+            cv2.line(image,(130,y),(700,y),(20,20,20),3)
+        result = detect_bounds(image,dpi=150, colour_cleanup=True)
+        self.assertGreater(result['bottom_px'],1000)
+        self.assertFalse(result.get('ruling_cleanup',False))
+
+
+if __name__ == '__main__':
+    unittest.main()