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Supported File Types

This page contains details about the file types that are supported by Vitessce, both those which can be loaded natively (by specifying file URLs in the view config) and those other file types for which conversion to native file types is straightforward. Use the tabs on the page to toggle between code snippets for JSON- and JavaScript API-based view configs.

Native File Types

Native file types are those which Vitessce can read directly from a static web server via a loader class. We welcome pull requests which implement loader classes to support additional file types natively.

AnnData as Zarr

Once your AnnData object has been written to a Zarr store, columns and keys in the original object (such as adata.obs["leiden"] or adata.obsm["X_umap"]) become relative file paths such as obs/leiden and obsm/X_umap. In the options property for file definitions in the Vitessce view config, you must specify which columns and keys will be used for visualization using POSIX-style paths.

note

The same Zarr store URL can be used for defining multiple files in the view config, for different data types and file types.

caution

The Zarr file types are not yet compatible with the Vitessce R package because Zarr is not yet supported in R.

anndata-cells.zarr

  • View config file definition snippet:

      ...,
      {
        "url": "http://example.com/my_store.zarr",
        "type": "cells",
        "fileType": "anndata-cells.zarr",
        "options": {
          // XY values represent spatial centroids, so values point to an array of tuples, one per observation/cell.
          "xy": "obsm/centroids",
          // Polygon values represent spatial segmentations, so values point to an array of arrays, one per observation/cell.
          "poly": "obsm/polygons",
          // Mappings define coordinates for scatterplot points - 
          // the original arrays may contain more than two dimensions per observation/cell,
          // so the dims property must slice these down to tuples.
          // This allows comparing the fourth and fifth principal components, for example.
          // The key immediately under mappings must be used in the coordination scopes.
          "mappings": {
            "UMAP": {
              "key": "obsm/umap",
              "dims": [ 0, 1 ]
            },
            "PCA": {
              "key": "obsm/pca",
              "dims": [ 4, 5 ]
            }
          },
          // Factors define per-observation annotations, like clustering results, to display in the popover.
          "factors": [
            "obs/leiden"
          ]
        }
      },
      ...

anndata-cell-sets.zarr

  • View config file definition snippet:

    {
        "url": "http://example.com/my_store.zarr",
        "type": "cell-sets",
        "fileType": "anndata-cell-sets.zarr",
        // Options defines which columns contain cell sets (clustering results) in the cell sets component.
        // The groupName is the display name and the setName is the path within the Zarr store.
        "options": [
          {
            "groupName": "Ledien",
            "setName": "obs/leiden"
          },
          {
            "groupName": "Cell Type",
            "setName": "obs/cell_type"
          },
        ]
      }

anndata-expression-matrix.zarr

  • View config file definition snippet:

    {
        "url": "http://example.com/my_store.zarr",
        "type": "expression-matrix",
        "fileType": "anndata-expression-matrix.zarr",
        "options": {
          "matrix": "X"
        }
      }
    While the expression matrix file loader does not fetch the entire matrix and store it in memory, displaying a heatmap will fetch whatever genes are needed for the heatmap. Similarly, selecting a gene to display over a scatterplot or spatial component can be costly if the expression matrix is not stored properly. In both cases, a poor chunking strategy can lead to too much data being requested for every gene selection/gene needed for the heatmap. If you experience performance issues, you may [use or store a subset of the matrix](#use-or-store-a-subset-of-x) to the Zarr store.

    The following snippet uses a Zarr store in which var/highly_variable provides a boolean filter of X for displaying a heatmap of highly variable genes:

    {
        "url": "http://example.com/my_store.zarr",
        "type": "expression-matrix",
        "fileType": "anndata-expression-matrix.zarr",
        "options": {
          // Matrix provides the location of an
          // obs-by-var (cell-by-gene) matrix to load into memory.
          "matrix": "obsm/X",
          // Matrix genes filter is a boolean list which defines
          // the subset of genes contained in the matrix to be visualized in the heatmap.
          // All of the genes in `var` will display in the `Genes` component though.
          // Use `geneFilter` instead if you only want to show a subset of the genes there
          // (this must be defined if the matrix is a subset of AnnData.X).
          "matrixGeneFilter": "var/highly_variable"
        }
      }

cells.json

  • JSON schema

  • JSON schema fixture

  • Example file

  • View config file definition snippet:

    {
        "url": "http://example.com/my_cells.json",
        "type": "cells",
        "fileType": "cells.json"
      }

cell-sets.json

  • JSON schema

  • JSON schema fixture

  • Example file

  • View config file definition snippet:

    {
        "url": "http://example.com/my_cell_sets.json",
        "type": "cell-sets",
        "fileType": "cell-sets.json"
      }

molecules.json

  • JSON schema

  • JSON schema fixture

  • Example file

  • View config file definition snippet:

    {
        "url": "http://example.com/my_molecules.json",
        "type": "molecules",
        "fileType": "molecules.json"
      }

genes.json

tip

The genes.json format is not very efficient from a file size perspective. For large expression matrices, we recommend using the more compact Zarr expression-matrix.zarr or anndata-expression-matrix.zarr formats.

  • JSON schema

  • JSON schema fixture

  • Example file

  • View config file definition snippet:

    {
        "url": "http://example.com/my_matrix_a.json",
        "type": "expression-matrix",
        "fileType": "genes.json"
      }

clusters.json

note

The name clusters.json is misleading; this file type is not intended to store clustering results (see cell-sets.json for storing clustering results). clusters.json is meant to store cell-by-gene expression matrices.

tip

The clusters.json format is not very efficient from a file size perspective. For large expression matrices, we recommend using the more compact Zarr expression-matrix.zarr or anndata-expression-matrix.zarr formats.

  • JSON schema

  • JSON schema fixture

  • Example file

  • View config file definition snippet:

    {
        "url": "http://example.com/my_matrix_b.json",
        "type": "expression-matrix",
        "fileType": "clusters.json"
      }

expression-matrix.zarr

  • View config file definition snippet:

    {
        "url": "http://example.com/my_matrix.zarr",
        "type": "expression-matrix",
        "fileType": "expression-matrix.zarr"
      }

raster.json

  • JSON schema for options

    note

    When defining image data with the raster.json file type, the main url property is not used. Instead, image URLs may be specified in the images array in the options property.

  • View config file definition snippet with an OME-TIFF image and segmentation bitmask:

    {
        "type": "raster",
        "fileType": "raster.json",
        "options": {
          "renderLayers": ["My OME-TIFF Image", "My OME-TIFF Mask"],
          "schemaVersion": "0.0.2",
          "images": [
            {
              "name": "My OME-TIFF Image",
              "url": "http://example.com/my_image.ome.tif",
              "type": "ome-tiff",
              "metadata": {
                "transform": {
                  // An optional transformation matrix
                  // in column-major order.
                  "matrix": [
                    0.81915098, -0.57357901, 0, 3264.76514684,
                    0.57357502, 0.819152, 0, 556.50440621,
                    0, 0, 1, 0,
                    0, 0, 0, 1
                  ]
                }
              }
            },
            {
              "name": "My OME-TIFF Mask",
              "url": "http://example.com/my_mask.ome.tif",
              "type": "ome-tiff",
              "metadata": {
                "isBitmask": true
              }
            }
          ]
        }
      }

  • View config file definition snippet with a Zarr store:

    {
        "type": "raster",
        "fileType": "raster.json",
        "options": {
          "schemaVersion": "0.0.2",
          "images": [
            {
              "name": "My Bioformats-Zarr Image",
              "url": "http://example.com/my_image.zarr",
              "type": "zarr",
              "metadata": {
                "dimensions": [
                  {
                    "field": "channel",
                    "type": "nominal",
                    "values": [
                      "DAPI - Hoechst (nuclei)",
                      "FITC - Laminin (basement membrane)",
                      "Cy3 - Synaptopodin (glomerular)",
                      "Cy5 - THP (thick limb)"
                    ]
                  },
                  {
                    "field": "y",
                    "type": "quantitative",
                    "values": null
                  },
                  {
                    "field": "x",
                    "type": "quantitative",
                    "values": null
                  }
                ],
                "isPyramid": true,
                "transform": {
                  "translate": {
                    "y": 0,
                    "x": 0
                  },
                  "scale": 1
                }
              }
            }
          ]
        }
      }

raster.ome-zarr

  • View config file definition snippet:

    {
        "url": "http://example.com/my_image.ome.zarr",
        "type": "raster",
        "fileType": "raster.ome-zarr"
      }

neighborhoods.json

  • JSON schema

  • JSON schema fixture

  • Example file

  • View config file definition snippet:

    {
        "url": "http://example.com/my_neighborhoods.json",
        "type": "neighborhoods",
        "fileType": "neighborhoods.json"
      }

genomic-profiles.zarr

  • View config file definition snippet:

    {
        "url": "http://example.com/my_genomic_profiles.zarr",
        "type": "genomic-profiles",
        "fileType": "genomic-profiles.zarr"
      }

Other File Types

Other file types must be converted to native file types prior to being used with Vitessce. Here we provide tips for conversion from common single-cell file types.

AnnData as h5ad

Convert to Zarr

Use AnnData's read_h5ad function to load the file as an AnnData object, then use the .write_zarr function to convert to a Zarr store. 

from anndata import read_h5ad
import zarr

adata = read_h5ad('path/to/my_dataset.h5ad')
adata.write_zarr('my_store.zarr')

Converted outputs can be used with the AnnData as Zarr family of native file types.

note

The ids in the obs part of the AnnData store must match the other data files with which you wish to coordinate outside the AnnData store. For example, if you have a bitmask that you wish to use with an AnnData store, the ids in obs need to be the very integers from each segmentation the bitmask.

Use or Store a subset of X

When the full expression matrix adata.X is large, there may be performance costs if Vitessce tries to load the full matrix for visualization, whether it be a heatmap or just loading genes to overlay on a spatial or scatterplot component. To offset this there are two things you can do:

  1. Use CSC format or chunk the zarr store efficiently (the later is recommended at the moment, see below) so that the UI remains responsive when selecting a gene to load into the client. Every time a gene is selected (or the heatmap is loaded), the client will use Zarr to fetch all the "cell x gene" information needed for rendering - however, a poor chunking strategy can result in too much data be loaded (and then not used). To remedy this, we recommend passing in the chunk_size argument to write_zarr so that the data is chunked in a manner that allows remote sources (like browsers) to fetch only the genes (and all cells) necessary for efficient display - to this end the chunk size is usually something like [num_cells, small_number] so every chunk contains all the cells, but only a few genes. That way, when you select a gene, only a small chunk of data is fetched for rendering and little is wasted. Ideally, at most one small request is made for every selection. You are welcome to try different chunking strategies as you see fit though!
  2. If only interested in a subset of the expression matrix for a heatmap, a filter (matrixGeneFilter in the view config) for the matrix can be stored as a boolean array in var. In this case, it is the highly_variable key from the sc.pp.highly_variable_genes call below. This will not alter the genes displayed in the Genes component (use geneFilter for that in the view config).
import scanpy as sc
from anndata import read_h5ad
import zarr

adata = read_h5ad('path/to/my_dataset.h5ad')

# Adds the `highly_variable` key to `var`
sc.pp.highly_variable_genes(adata, n_top_genes=200)
# If the matrix is sparse, it's best for performance to
# use non-sparse formats + chunking to keep the UI responsive.
# In the future, we should be able to use CSC sparse data natively
# and get equal performance with chunking:
# https://github.com/theislab/anndata/issues/524 
# but for now, it is still not as good (although not unusable).
if isinstance(adata.X, sparse.spmatrix):
    adata.X = adata.X.todense() # Or adata.X.tocsc() if you need to.
adata.write_zarr(zarr_path, [adata.shape[0], VAR_CHUNK_SIZE])  # VAR_CHUNK_SIZE should be something small like 10

Alternatively, a smaller matrix can be stored as multi-dimensional observation array in adata.obsm and used in conjunction with the geneFilter part of the view config.

sc.pp.highly_variable_genes(adata, n_top_genes=200)
adata.obsm['X_top_200_genes'] = adata[:, adata.var['highly_variable']].X.copy()
adata.write_zarr('my_store.zarr')

Converted outputs can be used with the AnnData as Zarr family of native file types. Both dense and sparse expression matrices are supported.

Loom

Convert to Zarr via AnnData

Use AnnData's read_loom function to load the Loom file as an AnnData object, then use the .write_zarr function to convert to a Zarr store. 

from anndata import read_loom

adata = read_loom(
  'path/to/my_dataset.loom',
  obsm_names={ "tSNE": ["_tSNE_1", "_tSNE_2"], "spatial": ["X", "Y"] }
)
adata.write_zarr('my_store.zarr')

Converted outputs can be used with the AnnData as Zarr family of native file types.

Seurat

The Vitessce R package can be used to convert Seurat objects to the cells.json and cell-sets.json file types.

SnapATAC

The Vitessce Python package can be used to convert SnapATAC outputs to the genomic-profiles.zarr, cells.json, and cell-sets.json file types.