A Clojure implementation of Blurhash.
Blurhash is an algorithm by Dag Ågren of Wolt that decodes an image to a very compact (~ 20-30 bytes) ASCII string representation, which can be then decoded into a blurred placeholder image. See the main repo for the rationale and details.
Both the encoder and decoder are implemented and work in both Clojure and ClojureScript.
The encode->hash->decode cycle looks something like this:
→ UIGuXeS@x[xX_MORbuoy?uNGM{nTNHMzIVnn →
The Clojure implementation is written in CLJC files, so that they can be used from Clojure and ClojureScript code alike.
You can encode an image to a blurhash using the function blurhash.encode/encode. It takes an image as an RGB matrix, currently represented as nested native vectors. The blurhash.core namespace contains (Clojure-specific) functions to convert an image file into a matrix, so you can do something like this:
(ns my-namespace
(:require [blurhash.core :refer [file->pixels]
[blurhash.encode :refer [encode]]]))
(def image
(file->pixels "./resources/example.jpg"))
(encode image)
=> "UIGuXeS@x[xX_MORbuoy?uNGM{nTNHMzIVnn"Here's an example of how to decode a blurhash into a placeholder image:
(ns my-namespace
(:require [blurhash.core :refer [pixels->file]
[blurhash.decode :refer [decode]]]))
(def blurred-image
(decode "UIGuXeS@x[xX_MORbuoy?uNGM{nTNHMzIVnn" 300 236))
(pixels->file blurred-image "blurred-image.jpg")
In ClojureScript (Reagent), you can decode a hash and render the placeholder like this:
(ns blurhash-example.core
(:require [reagent.core :as r]
[blurhash.decode :refer [decode]
[blurhash.util :as util]]))
(defn draw-canvas-contents [canvas]
(let [pixels (decode "UIGuXeS@x[xX_MORbuoy?uNGM{nTNHMzIVnn" 100 100)
ctx (.getContext canvas "2d")
imageData (.createImageData ctx 100 100)]
(do
(.set (. imageData -data) pixels)
(. ctx putImageData imageData 0 0))))
(defn div-with-canvas []
(let [dom-node (r/atom nil)]
(r/create-class
{:component-did-update
(fn [_]
(draw-canvas-contents (.-firstChild @dom-node)))
:component-did-mount
(fn [this]
(reset! dom-node (r/dom-node this)))
:reagent-render
(fn []
[:div
[:canvas (if-let [node @dom-node]
{:width (.-clientWidth node)
:height (.-clientHeight node)})]])})))
(defn home-page []
[:div [:h2 "Look at this blur!"]
[div-with-canvas]])
(defn mount-root []
(r/render [home-page] (.getElementById js/document "app")))
(defn init! []
(mount-root))
Copyright (c) 2019-2022 Tuomo Virolainen
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