The NFT Media Handler is an Elixir component in Blockscout responsible for fetching, resizing, and uploading NFT media files. It retrieves images and videos from URLs while handling errors and enforcing a size limit. It efficiently resizes images using the vix_vips library to generate various thumbnail sizes. If the original image is smaller than a target thumbnail size, resizing is skipped. For video files, it extracts the first frame to create a thumbnail image. It uploads media data to a cloud storage service using ExAws.S3. The component manages concurrent tasks with a GenServer and Task.Supervisor to optimize processing. It supports distributed processing through a round-robin node selection via a DispatcherInterface. The application is highly configurable through environment variables for different deployment scenarios.

Configuration

You can modify the application settings in the config/config.exs file. Key parameters include:

:enabled? - Enable/disable the application.
:remote? - Use remote mode.
:worker? - Enable worker mode.
:worker_concurrency - Number of concurrent tasks.
:worker_batch_size - Batch size for tasks.
:worker_spawn_tasks_timeout - Timeout between task spawns.
:tmp_dir - Temporary directory for storing files.

Project Structure

lib/nft_media_handler/application.ex - Main application module.
lib/nft_media_handler.ex - Main module for processing and uploading media.
lib/nft_media_handler/dispatcher.ex - Module for managing tasks.
lib/nft_media_handler/dispatcher_interface.ex - Interface for interacting with the dispatcher.
lib/nft_media_handler/image/resizer.ex - Module for resizing images.
lib/nft_media_handler/media/fetcher.ex - Module for fetching media from various sources.
lib/nft_media_handler/r2/uploader.ex - Module for uploading images to R2/S3.

Usage Examples

Resizing an Image

To resize an image, use the NFTMediaHandler.Image.Resizer.resize/3 function:

image = Vix.Vips.Image.new_from_file("path/to/image.jpg")
resized_images = NFTMediaHandler.Image.Resizer.resize(image, "http://example.com/image.jpg", ".jpg")

Uploading an Image

To upload an image, use the NFTMediaHandler.R2.Uploader.upload_image/3 function:

{:ok, result} = NFTMediaHandler.R2.Uploader.upload_image(image_binary, "image.jpg", "folder")

Fetching Media

To fetch media, use the NFTMediaHandler.Media.Fetcher.fetch_media/2 function:

{:ok, media_type, body} = NFTMediaHandler.Media.Fetcher.fetch_media("http://example.com/media.jpg", [])