And (def myfn (partial foo "bar")) is copying a pointer/reference to the value of foo, not all of the code of foo.

I'm trying to rotate an image with a transparent background an arbitrary amount of degrees (e.g. 261), and I don't care if I lose the corners of the image (they're empty anyways). I've found collage, ez-image and imgsclr but all seem to only support rotating in multiples of 90. Rotating and saving the image to disk are the only things I need. Any ideas?

because rotating fixed pixels 261 degrees is a bit harder 🙂

if i'd have to do it i'd probably implement it myself... just for the educational ride 🙂

@slack.jcpsantiago I believe clojure2d has a way to do that using the underlying Java Graphics2D library, however the API is not so friendly for doing pure image transformations

yep. should be possible just to tell graphics2d to draw a rotated image on an offscreen image buffer and capture the result from there

doesn't really look that hard

not sure about the outcome quality though, should probably check it out before you invest much time on it 🙂

Now I want to implement that, just for fun

It's really fun to work with linear algebra, which I assume would do the trick

(ns scratch
  (:require
   [clojure2d.core :as c2d]
   [ :as io])
  (:import [java.awt Graphics2D]
           [java.awt.image BufferedImage]
           [javax.imageio ImageIO]))

(defn rotate-around-center
  [img degrees]
  (let [w   (.getWidth img)
        h   (.getHeight img)]
    (c2d/with-canvas-> (c2d/canvas w h)
      (c2d/translate (/ w 2) (/ h 2))
      (c2d/rotate (* degrees (/ Math/PI 180)))
      (c2d/translate (- (/ w 2)) (- (/ h 2)))
      (c2d/image img)
      (c2d/get-image))))


(-> ""
  (io/as-url)
  (ImageIO/read)
  (rotate-around-center 261)
  (ImageIO/write "png" (io/as-file "out.png")))

that was quite painful 😶 gave up on wrangling with Graphics2D interop directly

wow wasn't expecting this to need such low level code, thanks for the interest guys

might be worth a PR to one of the above libraries to add arbitrary rotation support 🙂

@qythium that seems to the trick for me, but clojure2d seems to be discarding background transparency? source code says "Canvas is transparent by default." hum trying to figure that out, then need to figure out how to pay you a beer 😄

this is what I'm trying to rotate