Pillow/Tests/test_file_webp_alpha.py
2022-11-17 13:58:07 -08:00

155 lines
4.3 KiB
Python

import pytest
from PIL import Image
from .helper import (
assert_image_equal,
assert_image_similar,
assert_image_similar_tofile,
hopper,
)
_webp = pytest.importorskip("PIL._webp", reason="WebP support not installed")
def setup_module():
if _webp.WebPDecoderBuggyAlpha():
pytest.skip("Buggy early version of WebP installed, not testing transparency")
def test_read_rgba():
"""
Can we read an RGBA mode file without error?
Does it have the bits we expect?
"""
# Generated with `cwebp transparent.png -o transparent.webp`
file_path = "Tests/images/transparent.webp"
with Image.open(file_path) as image:
assert image.mode == "RGBA"
assert image.size == (200, 150)
assert image.format == "WEBP"
image.load()
image.getdata()
image.tobytes()
assert_image_similar_tofile(image, "Tests/images/transparent.png", 20.0)
def test_write_lossless_rgb(tmp_path):
"""
Can we write an RGBA mode file with lossless compression without error?
Does it have the bits we expect?
"""
temp_file = str(tmp_path / "temp.webp")
# temp_file = "temp.webp"
pil_image = hopper("RGBA")
mask = Image.new("RGBA", (64, 64), (128, 128, 128, 128))
# Add some partially transparent bits:
pil_image.paste(mask, (0, 0), mask)
pil_image.save(temp_file, lossless=True)
with Image.open(temp_file) as image:
image.load()
assert image.mode == "RGBA"
assert image.size == pil_image.size
assert image.format == "WEBP"
image.load()
image.getdata()
assert_image_equal(image, pil_image)
def test_write_rgba(tmp_path):
"""
Can we write a RGBA mode file to WebP without error.
Does it have the bits we expect?
"""
temp_file = str(tmp_path / "temp.webp")
pil_image = Image.new("RGBA", (10, 10), (255, 0, 0, 20))
pil_image.save(temp_file)
if _webp.WebPDecoderBuggyAlpha():
return
with Image.open(temp_file) as image:
image.load()
assert image.mode == "RGBA"
assert image.size == (10, 10)
assert image.format == "WEBP"
image.load()
image.getdata()
# Early versions of WebP are known to produce higher deviations:
# deal with it
if _webp.WebPDecoderVersion() <= 0x201:
assert_image_similar(image, pil_image, 3.0)
else:
assert_image_similar(image, pil_image, 1.0)
def test_write_rgba_keep_transparent(tmp_path):
"""
Can we write a RGBA mode file to WebP while preserving
the transparent RGB without error.
Does it have the bits we expect?
"""
temp_output_file = str(tmp_path / "temp.webp")
input_image = hopper("RGB")
# make a copy of the image
output_image = input_image.copy()
# make a single channel image with the same size as input_image
new_alpha = Image.new("L", input_image.size, 255)
# make the left half transparent
new_alpha.paste((0,), (0, 0, new_alpha.size[0]//2, new_alpha.size[1]))
# putalpha on output_image
output_image.putalpha(new_alpha)
# now save with transparent area preserved.
output_image.save(temp_output_file, "WEBP", exact=True, lossless=True)
# even though it is lossless, if we don't put exact=True, the transparent
# area will be filled with black (or something more conducive to compression)
with Image.open(temp_output_file) as image:
image.load()
assert image.mode == "RGBA"
assert image.format == "WEBP"
image.load()
image = image.convert("RGB")
assert_image_similar(image, input_image, 1.0)
def test_write_unsupported_mode_PA(tmp_path):
"""
Saving a palette-based file with transparency to WebP format
should work, and be similar to the original file.
"""
temp_file = str(tmp_path / "temp.webp")
file_path = "Tests/images/transparent.gif"
with Image.open(file_path) as im:
im.save(temp_file)
with Image.open(temp_file) as image:
assert image.mode == "RGBA"
assert image.size == (200, 150)
assert image.format == "WEBP"
image.load()
image.getdata()
with Image.open(file_path) as im:
target = im.convert("RGBA")
assert_image_similar(image, target, 25.0)