Description
Hi,
I recently ran pyvips.Image.icc_import on an image that didn't have a color profile and I was surprised to find that the command still worked. I expected an error, but after reading the documentation I see that the embedded option is only engaged if it's possible. I couldn't find documentation on what profile it's implicitly assuming, so I did a little (possibly flawed) experiment using numpy and pyvips:
In [1]: import numpy as np
In [2]: import pyvips
In [3]: im = np.c_[255 * np.eye(3, dtype=np.uint8), np.full(3, 255, dtype=np.uint8)].T[None]
In [4]: im # 1 row, 4 colums: red, green, blue and white pixels
Out[4]:
array([[[255, 0, 0],
[ 0, 255, 0],
[ 0, 0, 255],
[255, 255, 255]]], dtype=uint8)
In [5]: vim = pyvips.Image.new_from_array(im)
In [6]: vim
Out[6]: <pyvips.Image 4x1 uchar, 3 bands, srgb>
# Now I extract the chromaticity coordinates of these 4:
In [7]: vim.icc_import(pcs='xyz').colourspace('yxy').numpy().squeeze()[...,1:]
Out[7]:
array([[0.64086705, 0.33172554], # red primary
[0.31002232, 0.5852917 ], # green primary
[0.12321617, 0.05295137], # blue primary
[0.31268787, 0.32899842]], dtype=float32) # white
# embedded=True has no effect since there's no profile.
In [8]: vim.icc_import(pcs='xyz', embedded=True).colourspace('yxy').numpy().squeeze()[...,1:]
Out[8]:
array([[0.64086705, 0.33172554],
[0.31002232, 0.5852917 ],
[0.12321617, 0.05295137],
[0.31268787, 0.32899842]], dtype=float32)If Wikipedia can be trusted (?), this is close to, but not the same as, the sRGB primaries and whitepoint. In particular, the blue primary is listed there as x=0.15, y=0.06 while the value calculated above is x=0.12, y=0.05. At any rate I'm confused about the expected behavior when using icc_import without a color profile and whether the above is the expected output.
Many thanks in advance!