[BUG] zmin and zmax not working in imshow for 2d data

[emmanuelle]

See for example

import plotly.express as px
import numpy as np
img = np.random.random((10, 10))
px.imshow(img, zmin=0.3, zmax=0.7)

I think this is because the Heatmap trace uses instead the range_color argument which was quite introduced quite late in the process. It's easy to fix, we just have to decide first if the API is ok as it is.

[nicolaskruchten]

Conclusion from discussion: we should continue to use range_color if provided, but if it isn't, we insert zmin and zmax in its place.

[emmanuelle]

So of course it's a bit more complicated than I originally thought because in the coloraxis if you give cmin you must also give cmax (I don't see why, btw). Working on it!