tessellation-with-pixel-texture - IfcPixelTexture pixel binary data alpha position

[Andrej730]

@aothms

In IfcPixelTexture example opacity seems to be positioned at the highest byte - e.g. first pixel is 0FF000000 (FF alpha, white color with 100% alpha) but from IfcPixelTexture specs it seems that opacity should be at the lowest byte (e.g. 0x0000FF80 - 80 alpha, blue color with 50% alpha).

[aothms]

You're right as always andrej, not sure how this went unnoticed for over 10y, that surely shows something.

import ifcopenshell
pix = f.by_type('IfcPixelTexture')[0][8]
a = numpy.array(list(map(functools.partial(int, base=2), pix))).reshape((256, 256))[::-1,::1]
plt.imshow(a); plt.show()

a = numpy.array(list(map(lambda s: tuple(map(functools.partial(int, base=2), (s[8:16], s[16:24], s[24:32], s[0:8]))), pix))).reshape((256, 256, 4))[::-1,::1]
plt.imshow(a); plt.show()

Since I had the code here to do the byte swivelling, I just commited the fix (and fixed a serialization issue in ifcopenshell in the meantime).