The go-thumbhash library implements the Thumbhash image placeholder generation algorithm invented by Evan Wallace.

This algorithm is used to calculate a small binary hash representing an image using a Discrete Cosine Transform. The hash can then be used to generate a lossy representation of the original image.

The main use case is progressive loading of a web page containing lots of images, e.g. a photo gallery. Store the hash of each image in your database, and send it in the HTML document. On the client side, use Javascript (e.g. Evan Wallace's library) to generate a placeholder image from the hash. Then load the original image asynchronously.

Refer to the Go package documentation for information about the API.

See the thumbhash program for a practical use case.

Go-thumbhash is open source software distributed under the ISC license.