from io import BytesIO

from pathlib import Path

import pytest

from matplotlib.testing.decorators import image_comparison

from matplotlib import cm, pyplot as plt

@image_comparison(['pngsuite.png'], tol=0.09)

def test_pngsuite():

files = sorted(

(Path(__file__).parent / "baseline_images/pngsuite").glob("basn*.png"))

plt.figure(figsize=(len(files), 2))

for i, fname in enumerate(files):

data = plt.imread(fname)

cmap = None # use default colormap

if data.ndim == 2:

# keep grayscale images gray

cmap = cm.gray

# Using the old default data interpolation stage lets us

# continue to use the existing reference image

plt.imshow(data, extent=(i, i + 1, 0, 1), cmap=cmap,

interpolation_stage='data')

plt.gca().patch.set_facecolor("#ddffff")

plt.gca().set_xlim(0, len(files))

def test_truncated_file(tmp_path):

path = tmp_path / 'test.png'

path_t = tmp_path / 'test_truncated.png'

plt.savefig(path)

with open(path, 'rb') as fin:

buf = fin.read()

with open(path_t, 'wb') as fout:

fout.write(buf[:20])

with pytest.raises(Exception):

plt.imread(path_t)

def test_truncated_buffer():

b = BytesIO()

plt.savefig(b)

b.seek(0)

b2 = BytesIO(b.read(20))

b2.seek(0)

with pytest.raises(Exception):

plt.imread(b2)