Pixel-to-nanometer conversion is derivable from .zarr metadata, no need to specify in config file

[vreuter]

If it's specified, we should at least validate the specification against what we can glean from the .zarr metadata; otherwise, we can just infer this from the metadata. In particular, we can use voxel_size, axes, and unit together. Here's an example of the metadata:

$ cat .zattrs
{
    "metadata": {
        "channel_0": {
            "emissionLambdaNm": 700.5,
            "excitationLambdaNm": null,
            "name": "Far Red"
        },
        "channel_1": {
            "emissionLambdaNm": 630.0,
            "excitationLambdaNm": 561.0,
            "name": "Red"
        },
        "microscope": {
            "immersionRefractiveIndex": 1.515,
            "modalityFlags": [
                "fluorescence",
                "camera"
            ],
            "objectiveMagnification": 60.0,
            "objectiveName": 60.0,
            "objectiveNumericalAperture": 1.4,
            "zoomMagnification": 1.0
        },
        "voxel_size": [
            0.3,
            0.107325563330673,
            0.107325563330673
        ]
    },
    "multiscales": [
        {
            "axes": [
                {
                    "name": "t",
                    "type": "time",
                    "unit": "minute"
                },
                {
                    "name": "c",
                    "type": "channel"
                },
                {
                    "name": "z",
                    "type": "space",
                    "unit": "micrometer"
                },
                {
                    "name": "y",
                    "type": "space",
                    "unit": "micrometer"
                },
                {
                    "name": "x",
                    "type": "space",
                    "unit": "micrometer"
                }
            ],
            "datasets": [
                {
                    "coordinateTransformations": [
                        {
                            "scale": [
                                1.0,
                                1.0,
                                0.3,
                                0.107325563330673,
                                0.107325563330673
                            ],
                            "type": "scale"
                        }
                    ],
                    "path": "0"
                }
            ],
            "name": "seq_images_raw_zarr_P0002.zarr",
            "version": "0.4"
        }
    ]

[vreuter]

Look at mapping the unit name to a type and pairing with something like use of the squants library.