Adding upstream version 0.1.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tests/__init__.py

@@ -0,0 +1,80 @@
+"""
+Test suite for pydyf.
+
+This module adds a PNG export based on GhostScript, that is released under
+AGPL. As "the end user has the ability to opt out of installing the AGPL
+version of [Ghostscript] during the install process", and with explicit
+aggreement from Artifex, it is OK to distribute this code under BSD.
+
+See https://www.ghostscript.com/license.html.
+
+"""
+
+import io
+import os
+from pathlib import Path
+from subprocess import PIPE, run
+
+from PIL import Image
+
+PIXELS_BY_CHAR = dict(
+    _=(255, 255, 255),  # white
+    R=(255, 0, 0),  # red
+    B=(0, 0, 255),  # blue
+    G=(0, 255, 0),  # lime green
+    K=(0, 0, 0),  # black
+    z=None,  # any color
+)
+
+
+def assert_pixels(document, reference_pixels):
+    """Test that the rendered document matches the reference pixels."""
+
+    # Transform the PDF document into a list of RGB tuples
+    pdf = io.BytesIO()
+    document.write(pdf)
+    command = [
+        'gs', '-q', '-dNOPAUSE', '-dSAFER', '-sDEVICE=png16m',
+        '-r576', '-dDownScaleFactor=8', '-sOutputFile=-', '-']
+    png = run(command, input=pdf.getvalue(), stdout=PIPE).stdout
+    image = Image.open(io.BytesIO(png))
+    pixels = image.getdata()
+
+    # Transform reference drawings into a list of RGB tuples
+    lines = tuple(
+        line.strip() for line in reference_pixels.splitlines() if line.strip())
+    assert len({len(line) for line in lines}) == 1, (
+        'The lines of reference pixels don’t have the same length')
+    width, height = len(lines[0]), len(lines)
+    assert (width, height) == image.size, (
+        f'Reference size is {width}×{height}, '
+        f'output size is {image.width}×{image.height}')
+    reference_pixels = tuple(
+        PIXELS_BY_CHAR[char] for line in lines for char in line)
+
+    # Compare pixels
+    if pixels != reference_pixels:  # pragma: no cover
+        for i, (value, reference) in enumerate(zip(pixels, reference_pixels)):
+            if reference is None:
+                continue
+            if any(value != reference
+                   for value, reference in zip(value, reference)):
+                name = os.environ.get('PYTEST_CURRENT_TEST')
+                name = name.split(':')[-1].split(' ')[0]
+                write_png(f'{name}', pixels, width, height)
+                reference_pixels = [
+                    pixel or (255, 255, 255) for pixel in reference_pixels]
+                write_png(f'{name}-reference', reference_pixels, width, height)
+                x, y = i % width, i // width
+                assert 0, (
+                    f'Pixel ({x}, {y}) in {name}: '
+                    f'reference rgba{reference}, got rgba{value}')
+
+
+def write_png(name, pixels, width, height):  # pragma: no cover
+    """Take a pixel matrix and write a PNG file."""
+    directory = Path(__file__).parent / 'results'
+    directory.mkdir(exist_ok=True)
+    image = Image.new('RGB', (width, height))
+    image.putdata(pixels)
+    image.save(directory / f'{name}.png')