Automatic profile image preview

[lazka]

Currently the frontend hardcodes specific images for a signature profile and the width/height as configured in pdf-as. Ideally the activity would just get a profile ID to use, or figure out which profiles are available for the current user and everything else would be auto-magic.

pdf-as provides a visblock endpoint which provides a preview and allows selecting the profile and a resolution:

http://127.0.0.1:8080/pdf-as-web/visblock?r=100&p=BASE_NORMAL

esign could provide a "profiles" API which contains the profile name, size (can be derived from the vizblock)

profile:
  id: "my-profile"
  name: "My Profile"
  width: 123 (in points)
  height: 45 (in points)
  previewimage: "data:image/png;base64,..."
  supportsUserText: true

width/height could be derived from the image:

profile width/height: round((pixel / resolution) * 72) -> points

To do:

• add a profiles resource
• add a bundle config setting for a user visible profile name
• cache the profile image
• derive the width/height from it
• make visblock accessible in the firewall config
• expose if user text is configured

Open questions:

• name translation? -> leave up to the bundle config I guess?
• previewimage resolution? -> a multiple for 72 works nicely because of rounding, e.g. 360, or 504, use to calc width/height, and scale down.
• If we allow to extend the signature block the preview wont show that -> but that's already a problem
• We currently allow setting a different width when signing via the API, there is no way to get a preview for that though, unless we patch pdf-as. The frontend uses the default width though, so that's not a problem there.

All in all this would mean the following

<dbp-official-signature-pdf-upload
    signature-width="162"
    signature-height="28"
    signature-placeholder-image-src="official-signature-placeholder.png">
</dbp-official-signature-pdf-upload>

could be reduced to:

<dbp-official-signature-pdf-upload
    profile-id="official">
</dbp-official-signature-pdf-upload>