Allow named color palettes to be used by all sources.

[manthey]

This also increase the ability to handle css and named colors.

This generalized and supercedes #714. This closes #716.

[banesullivan]

This is excellent! However, I'm having some trouble getting this to work:

No problem:

>>> large_image.open('/Users/bane/Desktop/TC_NG_SFBay_US_Geo.tif', style=json.dumps({"band": 1, "palette": ["#000", "#f00"]}))
<large_image_source_gdal.GDALFileTileSource object at 0x7fa138fe3430>
>>>

Problem:

>>> large_image.open('/Users/bane/Desktop/TC_NG_SFBay_US_Geo.tif', style=json.dumps({"band": 1, "palette": "viridis"}))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/bane/Software/kw/large_image/large_image/tilesource/__init__.py", line 140, in open
    return getTileSource(*args, **kwargs)
  File "/Users/bane/Software/kw/large_image/large_image/tilesource/__init__.py", line 128, in getTileSource
    return getTileSourceFromDict(AvailableTileSources, *args, **kwargs)
  File "/Users/bane/Software/kw/large_image/large_image/tilesource/__init__.py", line 113, in getTileSourceFromDict
    sourceName = getSourceNameFromDict(availableSources, pathOrUri, *args, **kwargs)
  File "/Users/bane/Software/kw/large_image/large_image/tilesource/__init__.py", line 98, in getSourceNameFromDict
    if availableSources[sourceName].canRead(pathOrUri, *args, **kwargs):
  File "/Users/bane/Software/kw/large_image/large_image/tilesource/base.py", line 2360, in canRead
    cls(path, *args, **kwargs)
  File "/Users/bane/Software/kw/large_image/large_image/cache_util/cache.py", line 193, in __call__
    instance = super().__call__(*args, **kwargs)
  File "/Users/bane/Software/kw/large_image/sources/gdal/large_image_source_gdal/__init__.py", line 156, in __init__
    self._setDefaultStyle()
  File "/Users/bane/Software/kw/large_image/sources/gdal/large_image_source_gdal/__init__.py", line 227, in _setDefaultStyle
    bstyle['palette'] = self.getHexColors(bstyle['palette'])
  File "/Users/bane/Software/kw/large_image/sources/gdal/large_image_source_gdal/__init__.py", line 358, in getHexColors
    return ['#%02X%02X%02X%02X' % tuple(clr) for clr in palette]
  File "/Users/bane/Software/kw/large_image/sources/gdal/large_image_source_gdal/__init__.py", line 358, in <listcomp>
    return ['#%02X%02X%02X%02X' % tuple(clr) for clr in palette]
TypeError: %X format: an integer is required, not numpy.float64
>>>

[manthey]

Should be fixed and tested now.

[banesullivan]

IMO, this should be a ValueError. Any particular reason that TileSourceError is used here?

[manthey]

My thought was that it prevents the tile source from working, but I'll change it to a ValueError.

[banesullivan]

Would it make sense to fail back to a known value? For example, jet is a valid colormap if colorcet is installed. I'd prefer for this getPaletteColors to raise a ValueError if the named colormap does not exist and for large_image.open to safely fail back to a known palette issuing a warning if a bad palette name is passed

This might not be desired by everyone though...

[banesullivan]

Also could we implement an isValidPalette() function to let downstream packages quickly check a palette?

[manthey]

Also could we implement an isValidPalette() function to let downstream packages quickly check a palette?

Sure -- this would just be

try:
    large_image.tilesource.utilities.getPaletteColors(<value>)
    return True
except ValueError:
    return False

[banesullivan]

Could we also have a getAvailablePalettes() method to list all available named palettes - this would be particularly useful when making front-end that let you select from a list of colormaps. For example what I have here: https://tileserver.banesullivan.com/?band=2&min=&max=&palette=magma

[manthey]

Would it make sense to fail back to a known value? For example, jet is a valid colormap if colorcet is installed. I'd prefer for this getPaletteColors to raise a ValueError if the named colormap does not exist and for large_image.open to safely fail back to a known palette issuing a warning if a bad palette name is passed

I'd rather not. It seems like passing something like #fffff should throw, rather than produce something unexpected.

[banesullivan]

I'd rather not. It seems like passing something like #fffff should throw, rather than produce something unexpected.

Fair enough - leaving it as is works for me

[manthey]

Could we also have a getAvailablePalettes() method to list all available palettes - this would be particularly useful when making front-end that let you select from a list of colormaps. For example what I have here: https://tileserver.banesullivan.com/?band=2&min=&max=&palette=magma

Should such a function actually be called getAvailableNamedPalettes(), since it is basically a list of all of the palettable palettes and matplotlib palettes. Or, since you can pass a single color to get a palette, would such a function return named colors, too?

[banesullivan]

getAvailableNamedPalettes

I was just thinking that -- yes

would such a function return named colors, too?

I think so, I think anything named should be returned (e.g., "red", etc.)

[manthey]

getAvailableNamedPalettes

Let's push off adding getAvailableNamedPalettes into a separate PR.

[manthey]

@banesullivan There is a now a isValidPalette method.