Initial cropping support

tests/test_crop_blank_margins.py

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+import unittest
+
+import numpy as np
+import pymupdf
+
+from copienator.crop_blank_margins import apply_bounds
+
+
+class CropBlankMarginsTests(unittest.TestCase):
+    def test_cropbox_coordinates_with_rotation_and_existing_crop(self):
+        for rotation in (0, 90, 180, 270):
+            with self.subTest(rotation=rotation), pymupdf.open() as doc:
+                page = doc.new_page(width=600, height=800)
+                page.set_cropbox(pymupdf.Rect(30, 40, 570, 760))
+                page.set_rotation(rotation)
+                before = page.rect
+                page.insert_text((80, 220), 'Visible content', fontsize=20)
+                pix = page.get_pixmap()
+                original = np.frombuffer(pix.samples, np.uint8).reshape(pix.height, pix.width, 3)
+                apply_bounds(page, .2, .8)
+                self.assertAlmostEqual(page.rect.width, before.width)
+                self.assertAlmostEqual(page.rect.height, before.height*.6, places=3)
+                self.assertEqual(page.rotation, rotation)
+                pix = page.get_pixmap()
+                cropped = np.frombuffer(pix.samples, np.uint8).reshape(pix.height, pix.width, 3)
+                np.testing.assert_array_equal(cropped, original[int(before.height*.2):int(before.height*.8)])
+
+
+if __name__ == '__main__':
+    unittest.main()