Support for multi-arch docker images on size badge

[sh-cho]

📋 Description

![Docker Image Size (latest by date)](https://img.shields.io/docker/image-size/_/mysql/latest)

For example, mysql:latest image supports ["linux/amd64", "linux/arm64/v8"] os/architecture, but looks like I can't choose which one to use in the badge.

Is there any way to specify docker image's platform?

I can see docker version badge is available to select architecture with &arch=.. parameter.

[chris48s]

For the docker image size badge, we don't have an arch param and we also don't explicitly make an assumption about architecture. We just report the value of full_size, so if we look at

https://registry.hub.docker.com/v2/repositories/library/mysql/tags/latest

{
  "creator": 7,
  "id": 20021,
  "images": [
    {
      "architecture": "amd64",
      "features": "",
      "variant": null,
      "digest": "sha256:44f98f4dd825a945d2a6a4b7b2f14127b5d07c5aaa07d9d232c2b58936fb76dc",
      "os": "linux",
      "os_features": "",
      "os_version": null,
      "size": 131789857,
      "status": "active",
      "last_pulled": "2022-07-23T14:07:03.54267Z",
      "last_pushed": "2022-07-13T07:05:12.182358Z"
    },
    {
      "architecture": "arm64",
      "features": "",
      "variant": "v8",
      "digest": "sha256:12cf01a51f803d0ad49ee0dbbb3025a6eef3341e24757c2ed8150b6654c3fb07",
      "os": "linux",
      "os_features": "",
      "os_version": null,
      "size": 138716495,
      "status": "active",
      "last_pulled": "2022-07-23T08:20:42.387497Z",
      "last_pushed": "2022-07-13T08:05:31.345335Z"
    }
  ],
  "last_updated": "2022-07-13T08:05:52.466381Z",
  "last_updater": 1156886,
  "last_updater_username": "doijanky",
  "name": "latest",
  "repository": 21179,
  "full_size": 131789857,
  "v2": true,
  "tag_status": "active",
  "tag_last_pulled": "2022-07-23T14:07:03.54267Z",
  "tag_last_pushed": "2022-07-13T08:05:52.466381Z"
}

It looks like full_size in this case is the size of the amd64 image, but I'm not 100% sure what the rule is for how the API decides which image size to report there.

I think it would be reasonable to add an arch param to this endpoint, but if it is not specified, we just report the value of full_size (deferring to the DockerHub API's rules for deciding which image is the "default") if it is not specified.

[PaulaBarszcz]

I would like to work on this :)

[chris48s]

Cool - the post above should contain all the info. You can also have a look at the docker versions badge for some pointers (although this one should be a bit more straightforward!)