hv.RGB does not display image and fails to raise an error

[drrmmng]

The following code results in an error to raise a ValueError, so I think the problem is twofold. hv.RGB cannot handle the shape of the input array and neither can the error message. Maybe this is related to the fact that the image is monochrome?

Code section

to_img = torchvision.transforms.ToPILImage()
input_image = to_img(input.view([1, 28, -1]))
input_image  # correctly shows the image in a notebook

np.array(input_image).shape  # (28, 28)

plot = hv.RGB(np.array(input_image))  # error

plot2 = hv.Image(np.array(input_image))  # works but the colors are wrong (expected, I think)

error

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
 in 
     14 reconstruction = to_img(reconstruction)
     15 
---> 16 plot = hv.RGB(np.array(input_image))
     17 plot
     18 

~/anaconda3/lib/python3.7/site-packages/holoviews/element/raster.py in __init__(self, data, kdims, vdims, **params)
    736             if data.shape[-1] == 4 and len(vdims) == 3:
    737                 vdims.append(self.alpha_dimension)
--> 738         super(RGB, self).__init__(data, kdims=kdims, vdims=vdims, **params)
    739 
    740 

~/anaconda3/lib/python3.7/site-packages/holoviews/element/raster.py in __init__(self, data, kdims, vdims, bounds, extents, xdensity, ydensity, rtol, **params)
    285         elif isinstance(data, np.ndarray) and data.ndim < self._ndim:
    286             raise ValueError('%s type expects %d-D array received %d-D'
--> 287                              'array.' % (self._ndim, data.ndim))
    288 
    289         if rtol is not None:

TypeError: not enough arguments for format string

pyviz packages

colorcet                  2.0.1                      py_0    pyvizdatashader                0.7.0                      py_0    pyviz
holoviews                 1.12.3                     py_0    pyviz
hvplot                    0.4.0                      py_0    pyviz
panel                     0.5.1                      py_0    pyviz
param                     1.9.0                      py_0    pyviz
pyct                      0.4.6                      py_0    pyviz
pyct-core                 0.4.6                      py_0    pyviz
pyviz_comms               0.7.2                      py_0    pyviz

[philippjfr]

A monochrome image is by definition not an RGB image. If you want to display it as a monochrome image simply use hv.Image(np.array(input_image)).opts(cmap='gray')

[drrmmng]

Thank you.
But is the fact, that it fails to throw the ValueError intended?

[philippjfr]

No, you're right that is of course a bug.

[drrmmng]

Should I open a separate issue for that or should this be reopened?

[jlstevens]

I'll go ahead and reopen this issue.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.