three.js new lighting and color management - add colorspace to ImageTexture

[kielnino]

For the transition to the new lighting-model in three.js there were a few updates made to meshcat.

To render obj-files with textures correctly in this new version, the textures need to have the colorSpace attribute set accordingly (see discussion here). This MR adds the parameter to the json.

[kielnino]

I know that this can be also done via kwargs like this:

material = g.MeshLambertMaterial(map=g.ImageTexture(image=g.PngImage.from_file(texture_file), colorSpace="srgb"))

but as srgb is the new default, I would prefer to set it in the code directly.

[kielnino]

The same goes for the g.PointCloud. If we set the color as a numpy-array of RGB-colors, we now need to convert them to linear:

#suppose colors is a np.array of srgb values (range 0. - 1.) with shape (N, 3)

def srgb_to_linear(srgb):
    linear = np.where(srgb <= 0.0404482362771082, srgb / 12.92, ((srgb + 0.055) / 1.055) ** 2.4)
    return linear

colors_linear = srgb_to_linear(colors).T if colors is not None else None
g.PointCloud(position=points.T, color=colors_linear)