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import pytest
from PIL import Image, ImageMath, ImageMode
from .helper import convert_to_comparable, skip_unless_feature
codecs = dir(Image.core)
# There are several internal implementations
remarkable_factors = [
# special implementations
1,
2,
3,
4,
5,
6,
# 1xN implementation
(1, 2),
(1, 3),
(1, 4),
(1, 7),
# Nx1 implementation
(2, 1),
(3, 1),
(4, 1),
(7, 1),
# general implementation with different paths
(4, 6),
(5, 6),
(4, 7),
(5, 7),
(19, 17),
]
gradients_image = Image.open("Tests/images/radial_gradients.png")
gradients_image.load()
def test_args_factor():
im = Image.new("L", (10, 10))
assert (4, 4) == im.reduce(3).size
assert (4, 10) == im.reduce((3, 1)).size
assert (10, 4) == im.reduce((1, 3)).size
with pytest.raises(ValueError):
im.reduce(0)
with pytest.raises(TypeError):
im.reduce(2.0)
with pytest.raises(ValueError):
im.reduce((0, 10))
def test_args_box():
im = Image.new("L", (10, 10))
assert (5, 5) == im.reduce(2, (0, 0, 10, 10)).size
assert (1, 1) == im.reduce(2, (5, 5, 6, 6)).size
with pytest.raises(TypeError):
im.reduce(2, "stri")
with pytest.raises(TypeError):
im.reduce(2, 2)
with pytest.raises(ValueError):
im.reduce(2, (0, 0, 11, 10))
with pytest.raises(ValueError):
im.reduce(2, (0, 0, 10, 11))
with pytest.raises(ValueError):
im.reduce(2, (-1, 0, 10, 10))
with pytest.raises(ValueError):
im.reduce(2, (0, -1, 10, 10))
with pytest.raises(ValueError):
im.reduce(2, (0, 5, 10, 5))
with pytest.raises(ValueError):
im.reduce(2, (5, 0, 5, 10))
def test_unsupported_modes():
im = Image.new("P", (10, 10))
with pytest.raises(ValueError):
im.reduce(3)
im = Image.new("1", (10, 10))
with pytest.raises(ValueError):
im.reduce(3)
im = Image.new("I;16", (10, 10))
with pytest.raises(ValueError):
im.reduce(3)
def get_image(mode):
mode_info = ImageMode.getmode(mode)
if mode_info.basetype == "L":
bands = [gradients_image]
for _ in mode_info.bands[1:]:
# rotate previous image
band = bands[-1].transpose(Image.ROTATE_90)
bands.append(band)
# Correct alpha channel by transforming completely transparent pixels.
# Low alpha values also emphasize error after alpha multiplication.
if mode.endswith("A"):
bands[-1] = bands[-1].point(lambda x: int(85 + x / 1.5))
im = Image.merge(mode, bands)
else:
assert len(mode_info.bands) == 1
im = gradients_image.convert(mode)
# change the height to make a not-square image
return im.crop((0, 0, im.width, im.height - 5))
def compare_reduce_with_box(im, factor):
box = (11, 13, 146, 164)
reduced = im.reduce(factor, box=box)
reference = im.crop(box).reduce(factor)
assert reduced == reference
def compare_reduce_with_reference(im, factor, average_diff=0.4, max_diff=1):
"""Image.reduce() should look very similar to Image.resize(BOX).
A reference image is compiled from a large source area
and possible last column and last row.
+-----------+
|..........c|
|..........c|
|..........c|
|rrrrrrrrrrp|
+-----------+
"""
reduced = im.reduce(factor)
if not isinstance(factor, (list, tuple)):
factor = (factor, factor)
reference = Image.new(im.mode, reduced.size)
area_size = (im.size[0] // factor[0], im.size[1] // factor[1])
area_box = (0, 0, area_size[0] * factor[0], area_size[1] * factor[1])
area = im.resize(area_size, Image.BOX, area_box)
reference.paste(area, (0, 0))
if area_size[0] < reduced.size[0]:
assert reduced.size[0] - area_size[0] == 1
last_column_box = (area_box[2], 0, im.size[0], area_box[3])
last_column = im.resize((1, area_size[1]), Image.BOX, last_column_box)
reference.paste(last_column, (area_size[0], 0))
if area_size[1] < reduced.size[1]:
assert reduced.size[1] - area_size[1] == 1
last_row_box = (0, area_box[3], area_box[2], im.size[1])
last_row = im.resize((area_size[0], 1), Image.BOX, last_row_box)
reference.paste(last_row, (0, area_size[1]))
if area_size[0] < reduced.size[0] and area_size[1] < reduced.size[1]:
last_pixel_box = (area_box[2], area_box[3], im.size[0], im.size[1])
last_pixel = im.resize((1, 1), Image.BOX, last_pixel_box)
reference.paste(last_pixel, area_size)
assert_compare_images(reduced, reference, average_diff, max_diff)
def assert_compare_images(a, b, max_average_diff, max_diff=255):
assert a.mode == b.mode, f"got mode {repr(a.mode)}, expected {repr(b.mode)}"
assert a.size == b.size, f"got size {repr(a.size)}, expected {repr(b.size)}"
a, b = convert_to_comparable(a, b)
bands = ImageMode.getmode(a.mode).bands
for band, ach, bch in zip(bands, a.split(), b.split()):
ch_diff = ImageMath.eval("convert(abs(a - b), 'L')", a=ach, b=bch)
ch_hist = ch_diff.histogram()
average_diff = sum(i * num for i, num in enumerate(ch_hist)) / (
a.size[0] * a.size[1]
)
msg = (
f"average pixel value difference {average_diff:.4f} > "
f"expected {max_average_diff:.4f} for '{band}' band"
)
assert max_average_diff >= average_diff, msg
last_diff = [i for i, num in enumerate(ch_hist) if num > 0][-1]
assert max_diff >= last_diff, (
f"max pixel value difference {last_diff} > expected {max_diff} "
f"for '{band}' band"
)
def test_mode_L():
im = get_image("L")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_LA():
im = get_image("LA")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor, 0.8, 5)
# With opaque alpha, an error should be way smaller.
im.putalpha(Image.new("L", im.size, 255))
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_La():
im = get_image("La")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_RGB():
im = get_image("RGB")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_RGBA():
im = get_image("RGBA")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor, 0.8, 5)
# With opaque alpha, an error should be way smaller.
im.putalpha(Image.new("L", im.size, 255))
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_RGBa():
im = get_image("RGBa")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_I():
im = get_image("I")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor)
compare_reduce_with_box(im, factor)
def test_mode_F():
im = get_image("F")
for factor in remarkable_factors:
compare_reduce_with_reference(im, factor, 0, 0)
compare_reduce_with_box(im, factor)
@skip_unless_feature("jpg_2000")
def test_jpeg2k():
with Image.open("Tests/images/test-card-lossless.jp2") as im:
assert im.reduce(2).size == (320, 240)
|
