Rendering settings specification

Over the past few weeks we assembled a draft for a "rendering settings" specification (current spec: https://ngff.openmicroscopy.org/latest/#omero-md ); taking into account how OMERO stores rendering information, how other image formats handle it, and what information various clients / viewers need for rendering image data.

Here's an example how this could look like:

"renderingDefinition": {
   "@id": "renderingDef1"
   "groups": [
        {
            "views": ["view1", "view2"],
            "name": "Cycle1",
            "visible": true
        },
        {
            "views": ["view3"],
            "name": "Cycle2",
            "visible": true
        }
    ],
    "views": [
        {
            "@id": "view1",
            "dimension": [null, 0, null, null, null]  // (t,c,z,y,x)
            "visible": true,
            "mapping": {
               "family": "linear",
            }
            "color": {
                "format": "name",
                "type": "lut",
                "value": "brgbcmyw.lut"
            },
            "deviceSpaceMapping": {
                "reverseIntensity": false
            },
            "label": "GFP",
            "window": {
                "end": 188.89093017578125,
                "max": 188.89093017578125,
                "min": 0.007875712588429451,
                "start": 0.007875712588429451
            }
        },
        {
            "@id": "view2",
             "dimension": [null, 1, null, null, null],  // (t,c,z,y,x)
            "visible": false,
            "color": {
                "format": "hex",
                "type": "rgb",
                "value": "00FF00"
            },
            "deviceSpaceMapping": {
                "reverseIntensity": false
            },
            "mapping": {
               "family": "polynomial", // part of enumeration 
               "coefficient": 1.5,
               "noiseReduction": false,
            }
            "label": "DAPI",
            "window": {
                "end": 1542.5789794921875,
                "max": 1542.5789794921875,
                "min": 0.0,
                "start": 0.0
            }
        },
        {
            "@id": "view3",
            "dimension": [null, 2, null, null, null]  // (t,c,z,y,x)
            "visible": true,
            "color": {
                "format": "hex",
                "type": "rgb",
                "value": "FFFFFF"
            },
            "deviceSpaceMapping": {
                "reverseIntensity": false
            },
            "mapping": {
               "family": "linear",
            }
            "label": "OOOO",
            "window": {
                "end": 1555.0537109375,
                "max": 1555.0537109375,
                "min": 0.0,
                "start": 0.0
            }
        }
    ],
    // e.g. shape is (t,c,z,y,x)
    "defaultIndices": [5, null, "10:20", null, null],   // default view: t=5 and range 10-20 on z axis 
    "planarView": [3, 4], // we want to view y,x plane by default
    "zoom": 50 // percentage starting from highest resolution
}

RGB example

"renderingDefinition": {
   "@id": "renderingDef1"
   "groups": [
        {
            "views": ["view1", "view2", "view3"],
            "name": "The name you want to use",
            "visible": true,
            "metadata": {"rgb": true}
        }
    ],
    "views": [
        {
            "@id": "view1",
            "dimension": [null, 0, null, null, null]  // (t,c,z,y,x)
            "visible": true,
            "color": {
                "format": "hex",
                "type": "rgb",
                "value": "FF0000"
            },
            "label": "Red",
        },
        {
            "@id": "view2",
            "dimension": [null, 2, null, null, null]  // (t,c,z,y,x)
            "visible": true,
            "color": {
                "format": "hex",
                "type": "rgb",
                "value": "00FF00"
            },
            "label": "Green",
        },
        {
            "@id": "view3",
            "dimension": [null, 1, null, null, null]  // (t,c,z,y,x)
            "visible": true,
            "color": {
                "format": "hex",
                "type": "rgb",
                "value": "0000FF"
            },
            "label": "Blue",
        },
    ],
}

Comments, suggestions, etc. welcome!

(Similar issues #36 and #23)

concept like "defaultIndices" and dimension should allow the introduction of new dimension e.g. angle.

The concept of group can be used for example to "combine" channel like RGB, group view for some imaging modalities e.g. CyCIF

renderingDefinition is not mandatory. Currently no fields in renderingDefinition are mandatory.

An image could have multiple renderingDefinition per image

For color: see https://en.wikipedia.org/wiki/List_of_color_palettes and https://colorcet.holoviz.org/

• Support for one format only e.g. hex
  List of family: linear, logarithmic, exponential, polynomial

Start by reviewing the current OMERO metadata specification linked in the issue and compare it with the proposed renderingDefinition examples. Read related issues #36 and #23, then determine the required schema decisions and acceptance criteria; done would mean an agreed rendering-settings specification rather than an illustrative draft.