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Add contributing + changelog guidelines
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dstansby committed Nov 29, 2024
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6 changes: 6 additions & 0 deletions contributing/index.md
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# Contributing

## Minor changes or clarifications

Minor changes or clarifications to the specification should be made against the copy in the `latest` folder.
Please add a changelog entry explaining clearly the change you are making, so when a new version of the specifciation is released it is clear what has changed.
82 changes: 44 additions & 38 deletions latest/index.bs
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Expand Up @@ -52,8 +52,8 @@ Storage format {#storage-format}

OME-Zarr is implemented using the Zarr format as defined by the
[version 3 of the Zarr specification](https://zarr-specs.readthedocs.io/en/latest/v3/core/v3.0.html).
All features of the Zarr format including codecs, chunk grids, chunk
key encodings, data types and storage transformers may be used with
All features of the Zarr format including codecs, chunk grids, chunk
key encodings, data types and storage transformers may be used with
OME-Zarr unless explicitly disallowed in this specification.

An overview of the layout of an OME-Zarr fileset should make
Expand Down Expand Up @@ -87,7 +87,7 @@ Note that the number of dimensions is variable between 2 and 5 and that axis nam
│ ├── zarr.json # All image arrays must be up to 5-dimensional
│ │ # with the axis of type time before type channel, before spatial axes.
│ │
│ └─ ... # Chunks are stored conforming to the Zarr array specification and
│ └─ ... # Chunks are stored conforming to the Zarr array specification and
│ # metadata as specified in the array's `zarr.json`.
│
└── labels
Expand All @@ -106,7 +106,7 @@ Note that the number of dimensions is variable between 2 and 5 and that axis nam
│
├── 0 # Each multiscale level is stored as a separate Zarr array, as above, but only integer values
└── ... # are supported.

</pre>


Expand Down Expand Up @@ -143,7 +143,7 @@ A well group SHOULD NOT be present if there are no images in the well.
│ │ ├── 0 # First field of view of well A1
│ │ │ │
│ │ │ ├── zarr.json # Implements "multiscales", "omero"
│ │ │ ├── 0 # Resolution levels
│ │ │ ├── 0 # Resolution levels
│ │ │ ├── ...
│ │ │ └── labels # Labels (optional)
│ │ └── ... # Other fields of view
Expand All @@ -154,11 +154,11 @@ A well group SHOULD NOT be present if there are no images in the well.
OME-Zarr Metadata {#metadata}
=============================

The "OME-Zarr Metadata" contains metadata keys as specified below
The "OME-Zarr Metadata" contains metadata keys as specified below
for discovering certain types of data, especially images.

The OME-Zarr Metadata is stored in the various `zarr.json` files throughout the above array
hierarchy. In this file, the metadata is stored under the namespaced key
hierarchy. In this file, the metadata is stored under the namespaced key
`ome` in `attributes`.
The version of the OME-Zarr Metadata is denoted as a string in the `version` attribute within the `ome` namespace.

Expand Down Expand Up @@ -293,8 +293,8 @@ The transformations in the list are applied sequentially and in order.
"multiscales" metadata {#multiscale-md}
---------------------------------------

Metadata about an image can be found under the "multiscales" key in the group-level OME-Zarr Metadata.
Here, image refers to 2 to 5 dimensional data representing image or volumetric data with optional time or channel axes.
Metadata about an image can be found under the "multiscales" key in the group-level OME-Zarr Metadata.
Here, image refers to 2 to 5 dimensional data representing image or volumetric data with optional time or channel axes.
It is stored in a multiple resolution representation.

"multiscales" contains a list of dictionaries where each entry describes a multiscale image.
Expand Down Expand Up @@ -384,18 +384,18 @@ for more information.
"labels" metadata {#labels-md}
------------------------------

In OME-Zarr, Zarr arrays representing pixel-annotation data are stored in a group called "labels". Some applications--notably image segmentation--produce
a new image that is in the same coordinate system as a corresponding multiscale image (usually having the same dimensions and coordinate transformations).
This new image is composed of integer values corresponding to certain labels with custom meanings. For example, pixels take the value 1 or 0
if the corresponding pixel in the original image represents cellular space or intercellular space, respectively.
Such an image is referred to in this specification as a 'label image'.
In OME-Zarr, Zarr arrays representing pixel-annotation data are stored in a group called "labels". Some applications--notably image segmentation--produce
a new image that is in the same coordinate system as a corresponding multiscale image (usually having the same dimensions and coordinate transformations).
This new image is composed of integer values corresponding to certain labels with custom meanings. For example, pixels take the value 1 or 0
if the corresponding pixel in the original image represents cellular space or intercellular space, respectively.
Such an image is referred to in this specification as a 'label image'.

The "labels" group is nested within an image group, at the same level of the Zarr hierarchy as the resolution levels for the original image.
The "labels" group is not itself an image; it contains images. The pixels of the label images MUST be integer data types, i.e. one of
[`uint8`, `int8`, `uint16`, `int16`, `uint32`, `int32`, `uint64`, `int64`]. Intermediate groups between "labels" and the images within it are allowed,
The "labels" group is nested within an image group, at the same level of the Zarr hierarchy as the resolution levels for the original image.
The "labels" group is not itself an image; it contains images. The pixels of the label images MUST be integer data types, i.e. one of
[`uint8`, `int8`, `uint16`, `int16`, `uint32`, `int32`, `uint64`, `int64`]. Intermediate groups between "labels" and the images within it are allowed,
but these MUST NOT contain metadata. Names of the images in the "labels" group are arbitrary.

The OME-Zarr Metadata in the `zarr.json` file associated with the "labels" group MUST contain a JSON object with the key `labels`, whose value is a JSON array of paths to the
The OME-Zarr Metadata in the `zarr.json` file associated with the "labels" group MUST contain a JSON object with the key `labels`, whose value is a JSON array of paths to the
labeled multiscale image(s). All label images SHOULD be listed within this metadata file. For example:

```json
Expand All @@ -412,32 +412,32 @@ labeled multiscale image(s). All label images SHOULD be listed within this metad
}
```

The `zarr.json` file for the label image MUST implement the multiscales specification. Within the `multiscales` object, the JSON array
associated with the `datasets` key MUST have the same number of entries (scale levels) as the original unlabeled image.
The `zarr.json` file for the label image MUST implement the multiscales specification. Within the `multiscales` object, the JSON array
associated with the `datasets` key MUST have the same number of entries (scale levels) as the original unlabeled image.

In addition to the `multiscales` key, the OME-Zarr Metadata in this image-level `zarr.json` file SHOULD contain another key, `image-label`,
whose value is also a JSON object. The `image-label` object stores information about the display colors, source image, and optionally,
further arbitrary properties of the label image. That `image-label` object SHOULD contain the following keys: first, a `colors` key,
whose value MUST be a JSON array describing color information for the unique label values. Second, a `version` key, whose value MUST be a
In addition to the `multiscales` key, the OME-Zarr Metadata in this image-level `zarr.json` file SHOULD contain another key, `image-label`,
whose value is also a JSON object. The `image-label` object stores information about the display colors, source image, and optionally,
further arbitrary properties of the label image. That `image-label` object SHOULD contain the following keys: first, a `colors` key,
whose value MUST be a JSON array describing color information for the unique label values. Second, a `version` key, whose value MUST be a
string specifying the version of the OME-Zarr `image-label` schema.

Conforming readers SHOULD display labels using the colors specified by the `colors` JSON array, as follows. This array contains one
JSON object for each unique custom label. Each of these objects MUST contain the `label-value` key, whose value MUST be the integer
corresponding to a particular label. In addition to the `label-value` key, the objects in this array MAY contain an `rgba` key whose
value MUST be an array of four integers between 0 and 255, inclusive. These integers represent the `uint8` values of red, green, and
blue that comprise the final color to be displayed at the pixels with this label. The fourth integer in the `rgba` array represents alpha,
or the opacity of the color. Additional keys under `colors` are allowed.
Conforming readers SHOULD display labels using the colors specified by the `colors` JSON array, as follows. This array contains one
JSON object for each unique custom label. Each of these objects MUST contain the `label-value` key, whose value MUST be the integer
corresponding to a particular label. In addition to the `label-value` key, the objects in this array MAY contain an `rgba` key whose
value MUST be an array of four integers between 0 and 255, inclusive. These integers represent the `uint8` values of red, green, and
blue that comprise the final color to be displayed at the pixels with this label. The fourth integer in the `rgba` array represents alpha,
or the opacity of the color. Additional keys under `colors` are allowed.

Next, the `image-label` object MAY contain the following keys: a `properties` key, and a `source` key.

Like the `colors` key, the value of the `properties` key MUST be an array of JSON objects describing the set of unique possible pixel values.
Each object in the `properties` array MUST contain the `label-value` key, whose value again MUST be an integer specifying the pixel value for that label.
Additionally, an arbitrary number of key-value pairs MAY be present for each label value, denoting arbitrary metadata associated with that label.
Like the `colors` key, the value of the `properties` key MUST be an array of JSON objects describing the set of unique possible pixel values.
Each object in the `properties` array MUST contain the `label-value` key, whose value again MUST be an integer specifying the pixel value for that label.
Additionally, an arbitrary number of key-value pairs MAY be present for each label value, denoting arbitrary metadata associated with that label.
Label-value objects within the `properties` array do not need to have the same keys.

The value of the `source` key MUST be a JSON object containing information about the original image from which the label image derives.
This object MAY include a key `image`, whose value MUST be a string specifying the relative path to a Zarr image group.
The default value is `../../` since most labeled images are stored in a "labels" group that is nested within the original image group.
The value of the `source` key MUST be a JSON object containing information about the original image from which the label image derives.
This object MAY include a key `image`, whose value MUST be a string specifying the relative path to a Zarr image group.
The default value is `../../` since most labeled images are stored in a "labels" group that is nested within the original image group.

Here is an example of a simple `image-label` object for a label image in which 0s and 1s represent intercellular and cellular space, respectively:

Expand All @@ -446,8 +446,8 @@ path: examples/label_strict/colors_properties.json
highlight: json
</pre>

In this case, the pixels consisting of a 0 in the Zarr array will be displayed as 50% blue and 50% opacity. Pixels with a 1 in the Zarr array,
which correspond to cellular space, will be displayed as 50% green and 50% opacity.
In this case, the pixels consisting of a 0 in the Zarr array will be displayed as 50% blue and 50% opacity. Pixels with a 1 in the Zarr array,
which correspond to cellular space, will be displayed as 50% green and 50% opacity.

"plate" metadata {#plate-md}
----------------------------
Expand Down Expand Up @@ -564,6 +564,12 @@ Multi-word keys in this specification should use the `camelCase` style.
NB: some parts of the specification don't obey this convention as they
were added before this was adopted, but they should be updated in due course.

Changelog
=========

Next version (unreleased)
-------------------------

Implementations {#implementations}
==================================

Expand Down

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