Serving image via output stream with ningle, running on woo

imger.lisp

(ql:quickload :clack :silent t)
(ql:quickload :vecto :silent t)
(ql:quickload :ningle :silent t)
(ql:quickload :babel :silent t)
(ql:quickload :babel-streams :silent t)

(in-package :cl-user)

(defpackage imger
  (:use :cl :ningle :babel :babel-streams :vecto)
  (:import-from :lack.response
    :response-status
    :response-headers)
  (:import-from :ningle
    :*response*)
  (:import-from :babel-streams
    :with-output-to-sequence)
  (:import-from :vecto
    :with-canvas
    :set-rgb-fill
    :clear-canvas
    :save-png-stream)
  (:export :start)
)

(in-package :imger)

(defvar *app* (make-instance '<app>))
(defvar *h* nil)

(defmacro n-param (param params)
  `(parse-integer (cdr (assoc ,param ,params))))

(defun serve-image (params)
  (let ((w (n-param :w params))
        (h (n-param :h params)))
    (progn
      (setf (response-status *response*) 200)
      (setf (getf (response-headers *response*) :content-type) "image/png")
      (with-output-to-sequence (s)
                               (with-canvas (:width w :height h)
                                            (set-rgb-fill 0.2 0.2 0.9)
                                            (clear-canvas)
                                            (save-png-stream s))
                               :element-type '(unsigned-byte 8)))))

(setf (route *app* "/i/:w/:h") #'serve-image)

(defun start ()
  (setf *h* (clack:clackup *app* :server :woo)))