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Experimenting with some basic image dithering, in the style of 10 PRINT (see also, the idea was inspired by _bitcraft's_ OpenProcessing version:
(ns enchilada.image-dither
(:require-macros [cljs.core.async.macros :refer [go]])
[enchilada :refer [canvas ctx value-of canvas-size proxy-request]]
[cljs.core.async :as async :refer [<!]]
[dataview.loader :refer [fetch-image]]
[jayq.core :refer [show]]
[big-bang.core :refer [big-bang]]
[ :refer [client-coords]]
[monet.canvas :refer [draw-image]]))
(def images
; TODO: move into
(defn touch-coords [event]
(when-let [touch-object (.-changedTouches event)]
(client-coords (aget touch-object 0))))
(defn resize [dest src {:keys [w h]}]
(let [ctx (.getContext dest "2d")
temp-canvas (.createElement js/document "canvas")
temp-ctx (.getContext temp-canvas "2d")]
(set! (.-width temp-canvas) (.-width src))
(set! (.-height temp-canvas) (.-height src))
(draw-image temp-ctx src {:x 0 :y 0})
(draw-image ctx temp-canvas
{:sx 0 :sy 0 :sw (.-width temp-canvas) :sh (.-height temp-canvas)
:dx 0 :dy 0 :dw w :dh h })
; TODO remove temp-canvas?
(defn sample [src new-width]
(let [ratio (/ (.-height src) (.-width src))
new-height (* ratio new-width)
dest (.createElement js/document "canvas")]
(set! (.-width dest) new-width)
(set! (.-height dest) new-height)
(resize dest src {:w new-width :h new-height})))
(defn rotate [coll]
(vec (next coll))
(first coll)))
(defn constrain [amt low high]
(< amt low) low
(> amt high) high
:else amt))
(defn handle-mousemove [event {:keys [width] :as world-state}]
(let [mouse-x (first (or (touch-coords event) (client-coords event)))]
(assoc world-state :m (constrain (/ (* 130 (- mouse-x 200)) (* 2 width)) 1 129))))
(defn next-resolution [event {:keys [resolutions width image] :as world-state}]
(let [n (first resolutions)]
:n n
:d (/ width n)
:sample (sample image n)
:resolutions (rotate resolutions)))))
(defn next-effect [event {:keys [effects] :as world-state}]
(if (= (.-keyCode event) 67) ; 'C' key
(assoc world-state :effects (rotate effects))
(defn brightness [pixels x y w]
(let [offset (* 4 (+ (* y w) x))
r (aget pixels offset)
g (aget pixels (inc offset))
b (aget pixels (+ offset 2))]
(/ (+ r g b) 3)))
(defn brightness! [pixels x y w value]
(let [offset (* 4 (+ (* y w) x))]
(aset pixels offset value)
(aset pixels (inc offset) value)
(aset pixels (+ offset 2) value)
(aset pixels (+ offset 3) 0xff)))
(defn diagonal [value dx dy d m]
(let [value (- 0xff value)
z (if (< (mod value (* 2 m)) m)
(/ (* (+ dx dy 1) 0xff) d)
(/ (* (- (+ dx d) dy) 0xff) d))]
(if (> value (+ (* 2 (Math/abs (- z 0xff) 2)))) 0x00 0xff)))
(defn inverse [value dx dy d m]
(- 0xff value))
(defn threshold [value dx dy d m]
(if (> value (* 2 m)) 0x00 0xff))
(defn solarize [value dx dy d m]
(let [a 1
b -4
c 4
x (/ value 0xff)]
(* 0xff (+ a (* b x) (* c x x)))))
(defn render [{:keys [m d n sample image ratio width effects] :as world-state}]
(let [sample-ctx (.getContext sample "2d")
sample-data (.-data (.getImageData sample-ctx 0 0 n (inc (Math/floor (* n ratio)))))
pixels (.getImageData ctx 0 0 width (* width ratio))
pixel-data (.-data pixels)
effect (first effects)]
(dotimes [y (inc (Math/floor (* n ratio)))]
(dotimes [x n]
(let [value (brightness sample-data x y n)
x (* x d)
y (* y d)]
(dotimes [dy d]
(dotimes [dx d]
(+ x dx)
(+ y dy)
(effect value dx dy d m)))))))
(.putImageData ctx pixels 0 0)))
(let [width 400
img (<! (fetch-image (proxy-request (rand-nth images))))
sample (sample img width)
initial-state (next-resolution nil
{:m 6
:width width
:ratio (/ (.-height img) (.-width img))
:image img
:resolutions [50 100 50 25 20 25]
:effects [diagonal identity inverse solarize]})]
(set! (.-height (.get canvas 0)) (.-height sample))
(show canvas)
(draw-image ctx sample {:x width :y 0})
(render initial-state)
;:event-target canvas
:initial-state initial-state
:on-keydown next-effect
:on-mousedown next-resolution
:on-mousemove handle-mousemove
:to-draw render)))
  • Move the mouse horizontally to change threshold point
  • Click the mouse to alter the resolution
  • Press the 'C' key to cycle between [10-Print, Greyscale, Inverse, Solarize]
  • Refresh the page for a different image (chosen at random)
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