Azure Functions App to generate "smart" thumbnails for uploaded images, using the Azure Computer Vision API.
ProcessThumbnail: Function that generates "smart" thumbnails for images using the Vision API. It defaults to a 150x150 thumbnail size, and can be overridden in the Application Settings.
ProcessResize: Function that scales down images if they are too big. This is because the computer vision api may fail with big images, so this function pre-processes images that are wider or higher than the maximum media size (defaults to 1200px, also overridden by App Settings).
There are two http-triggered functions to allow integration with api consumers:
Upload (GET /api/upload)
Gets a SAS token to upload a file to a pre-defined container (defaults to uploads and can be overridden by AppSettings).
Requires a x-blob-filename header containing the name of the file to upload.
RequestThumbnail (POST /api/thumbnail)
Puts a message in the media-thumbnail-signal queue to request a thumbnail generation.
Requires a x-blob-path header containing the path of the blob (including the container name). This value will be used as the message content.
The "main" Thumbnail function is triggered by a simple string message in a media-thumbnail-signal queue, which contains the full path of an image blob in Blob Storage (in the form of {container}/{blob name}).
If the image is bigger that the maximum configured size, a new message is put on a media-resize-signal and it gets picked up by the Resize function, which creates a new blob for the resized image. Next, a new message is put on the thumbnail signal queue (with the new blob's path) to start a new flow.