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Image Sources

go-dims supports multiple source backends for fetching original images: http, s3, and file.

You can explicitly specify the backend using a scheme-style prefix:

  • http://example.com/image.jpg
  • s3://bucket/key/image.jpg
  • file://path/to/image.jpg

If the URL does not include a scheme prefix (e.g., just ?url=cat.jpg), go-dims will fall back to the backend defined by:

DIMS_DEFAULT_SOURCE_BACKEND​

  • Default: http

To support simplified URLs with S3 or file sources, you must set that backend as the default:

DIMS_DEFAULT_SOURCE_BACKEND=s3

This allows you to make requests like:

?url=my-folder/image.jpg

And go-dims will resolve it using the configured S3.

DIMS_ALLOWED_SOURCE_BACKENDS​

Comma-separated list of backends that are permitted.

  • Default: http

Only the specified backends will be allowed to handle requests. If a backend is not listed, requests using that scheme will return an error.

note

By default, s3 and file are disabled. You must explicitly enable them to allow access.

DIMS_ALLOWED_SOURCE_BACKENDS=http,s3

To allow all supported backends:

DIMS_ALLOWED_SOURCE_BACKENDS=http,s3,file

S3 Source Configuration​

Enable fetching images from Amazon S3 by configuring the following variables:

DIMS_S3_BUCKET​

The S3 bucket name from which to fetch images.

  • Default: (empty)

DIMS_S3_PREFIX​

Optional prefix to apply to all S3 object keys.

  • Default: (empty)

This is useful if you store images in a specific folder or namespace within your bucket.

Example:

DIMS_S3_BUCKET=my-bucket  
DIMS_S3_PREFIX=images/2024/

A request for image.jpg would resolve to s3://my-bucket/images/2024/image.jpg.

File Source Configuration​

Enable local file access (useful for development or staging).

DIMS_FILE_BASE_DIR​

Specifies the base directory for reading local files.

  • Default: ./resources

Example:

DIMS_FILE_BASE_DIR=/var/images

A request for sample.jpg would resolve to /var/images/sample.jpg.