def compress(img_path: str, b: int, out_path: str) -> str:
"""
Compresses an image into a format with bits to
represent each channel. Saves the image and returns
the path to compressed output image specified by the out_path.
Parameters:
----------
img_path: str (file path to a .png image)
b: int in [1, 8]
out_path: str (file path to the compressed png image)
Returns:
-------
compressed_img : str (file path to the image with each channel
compressed to b bits, same as out_path)
Examples:
-------
>>> imageCompress.compress("..//image.png", b = 5, "..//compressed_image.png")
>>> "..//compressed_image.png"
"""
if type(img_path) != str:
raise TypeError(
"Input image path type not correct, make sure you are passing a string!"
)
if type(out_path) != str:
raise TypeError(
"Output path type not correct, make sure you are passing a string!"
)
if type(b) != int:
raise TypeError("b should be a positive integer <= 8!")
if b <= 0:
raise ValueError(
"b should be a positive integer greater than 0 and less than 9!")
if b > 8:
raise ValueError("b should be a positive integer <= 8!")
min_size_img = compression(
img_path, 1,
os.path.join((os.path.dirname(os.path.abspath(img_path))), "1.png"))
desired_size_img = compression(
img_path, b,
os.path.join((os.path.dirname(os.path.abspath(img_path))), "2.png"))
if image_size(min_size_img) > image_size(img_path):
os.remove(min_size_img)
os.remove(desired_size_img)
raise Exception("The image is already compressed")
elif image_size(desired_size_img) > image_size(img_path):
os.remove(min_size_img)
os.remove(desired_size_img)
raise Exception("Choose a smaller b to compress the image.")
else:
os.remove(min_size_img)
os.remove(desired_size_img)
return compression(img_path, b, out_path)
def compress(img_path, b, out_path):
"""
Compresses an image into a format with bits to
represent each channel.
Parameters:
----------
img_path: str (file path to a .png image)
b: int in [1, 8]
out_path: str (file path to the compressed png image)
Returns:
-------
compressed_img : str (file path to the image with each channel
compressed to b bits, same as out_path)
"""
if type(img_path) != str or type(out_path) != str:
raise TypeError(
"Image path not correct, make sure you are passing a string!")
if type(b) != int:
raise TypeError("b should be a positive integer <= 8!")
if b <= 0 or b > 8:
raise ValueError("b should be a positive integer <= 8!")
min_size_img = compression(
img_path, 1,
os.path.join((os.path.dirname(os.path.abspath(img_path))), "1.png"))
desired_size_img = compression(
img_path, b,
os.path.join((os.path.dirname(os.path.abspath(img_path))), "2.png"))
if image_size(min_size_img) > image_size(img_path):
os.remove(min_size_img)
os.remove(desired_size_img)
raise Exception("The image is already compressed")
elif image_size(desired_size_img) > image_size(img_path):
os.remove(min_size_img)
os.remove(desired_size_img)
raise Exception("Choose a smaller b to compress the image.")
else:
os.remove(min_size_img)
os.remove(desired_size_img)
return compression(img_path, b, out_path)
def test_size_type(self):
'''
Function to test that a TypeError is raised when invalid type is passed in
as image
'''
with pytest.raises(TypeError):
image_size(imread(img_path))
with pytest.raises(TypeError):
image_size(True)
with pytest.raises(TypeError):
image_size(123)
with pytest.raises(TypeError):
image_size(12.2)
def test_compress_size(self):
'''
Function to test that the size of the compressed image
is correct
'''
compressed_img = compress(img_path, 3, outpath)
assert image_size(compressed_img) < 7 / 8 * image_size(img_path)
compressed_img = compress(img_path, 1, outpath)
assert image_size(compressed_img) < 5 / 8 * image_size(img_path)
compressed_img = compress(img_path, 6, outpath)
assert image_size(compressed_img) <= 8 / 8 * image_size(img_path)
compressed_img = compress(img_path, 8, outpath)
assert image_size(compressed_img) <= image_size(img_path)
def test_size_output(self):
'''
Function to test that correct size is returned
'''
assert image_size(img_path) <= 1.1 * imread(img_path).nbytes