Always marshal tile metadata on presence of pyramid

[chris-allan]

It is possible, in particular for floating point data, that a pyramid is
present even if the server thinks a pyramid is not required. The
condition for tile metadata being available is now pyramid presence.

See:

• Presence of existing pyramids for floating point data masked omero-romio#24
• Always marshal tile metadata on presence of pyramid omero-web#193

[chris-allan]

Additional requirement for restoring all the pyramid metadata that was started in ome/omero-web#193.

/cc @sbesson

[joshmoore]

The change seems straight-forward enough, though I imagine we should clarify in https://github.com/ome/omero-blitz/blob/master/src/main/slice/omero/api/PyramidService.ice when each of the methods should be used.

[chris-allan]

@joshmoore: Yeah, in particular requirePixelsPyramid() as currently documented is already largely incorrect:

• https://github.com/ome/omero-blitz/blob/master/src/main/slice/omero/api/PyramidService.ice#L38

[sbesson]

Tested with the same sample floating-point multi-resolution image as the one noted in ome/omero-web#193

Without this PR, the marshalled image data for this image is:

 "tiles": true,
  "tile_size": {
    "width": 1024,
    "height": 1024
  },
  "levels": 5,
  "interpolate": true,
  "size": {
    "width": 7676,
    "height": 7420,
    "z": 38,
    "t": 1,
    "c": 1
  },
  "pixel_size": {
    "x": 0.00006375423073768616,
    "y": 0.00006375423073768616,
    "z": 1
  },
  "init_zoom": 0,
  "nominalMagnification": 105000,
  "pixel_range": [
    -2147483648,
    2147483647
  ],

With this PR included

  "tiles": true,
  "tile_size": {
    "width": 1024,
    "height": 1024
  },
  "levels": 5,
  "zoomLevelScaling": {
    "0": 1,
    "1": 0.5,
    "2": 0.25,
    "3": 0.12493486190724336,
    "4": 0.06240229286086504
  },
  "interpolate": true,
  "size": {
    "width": 7676,
    "height": 7420,
    "z": 38,
    "t": 1,
    "c": 1
  },
  "pixel_size": {
    "x": 0.00006375423073768616,
    "y": 0.00006375423073768616,
    "z": 1
  },
  "init_zoom": 0,
  "nominalMagnification": 105000,
  "pixel_range": [
    -2147483648,
    2147483647
  ],

So the proposed change is functional, is inline with the fix already released in the latest omero-web patch release.

While reviewing #239 (comment), I also found the getResolutionLevels docstring includes a caveat about the usage of this API https://github.com/ome/omero-blitz/blob/master/src/main/slice/omero/api/PyramidService.ice#L43. Any thought on whether this limitation is still applicable and should change the beheavior of this gateway API? If no longer valid, it can probably be reviewed together with the documentation of requiresPixelsPyramid.

Once the question above is cleared, proposing to get this merged for inclusion in the upcoming omero-py minor release.