#!/usr/bin/env -S guile -e main -s
!#
;;; extract-green-color --- Extract green color from a photo of LCD Writing Tablet.
;;; Copyright © 2021 Masaya Tojo <masaya@tojo.tokyo>
;;;
;;; This file is part of extract-green-color.
;;;
;;; Extract-green-color is free software; you can redistribute
;;; it and/or modify it under the terms of the GNU General Public
;;; License as published by the Free Software Foundation; either
;;; version 3 of the License, or (at your option) any later version.
;;;
;;; Extract-green-color is distributed in the hope that it will
;;; be useful, but WITHOUT ANY WARRANTY; without even the implied
;;; warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
;;; See the GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with extract-green-color.  If not, see
;;; <http://www.gnu.org/licenses/>.

(use-modules (cv)
             ((cv idata) #:prefix idata:)
             (srfi srfi-8)
             (ice-9 getopt-long)
             (ice-9 match))

(define (rgb->hsv r g b)
  (let* ((max* (max r g b))
         (min* (min r g b)) (max-min* (- max* min*)))
    (let ((h (cond
              ((= max* min*) #f)
              ((= b min*) (+ (* 60 (/ (- g r) max-min*)) 60))
              ((= r min*) (+ (* 60 (/ (- b g) max-min*)) 180))
              (else       (+ (* 60 (/ (- r b) max-min*)) 300))))
          (s (/ max-min* max*))
          (v (/ max* 256.0)))
      (values h s v))))

(define (im-resize* img new-w)
  (match img
    ((w h _ _)
     (im-resize img new-w (floor (* h (/ new-w w)))))))

(define* (extract-green-color img
                              hue-minus-threshold
                              hue-plus-threshold
                              saturation-threshold
                              value-treshold)
  (match img
    ((w h _ _)
     (let ((out (im-make w h 3 0)))
       (do ((i 0 (1+ i)))
           ((= i h))
         (do ((j 0 (1+ j)))
             ((= j w))
           (let ((r (im-fast-ref img i j 0))
                 (g (im-fast-ref img i j 1))
                 (b (im-fast-ref img i j 2)))
             (receive (h s v) (rgb->hsv r g b)
               (when (and h
                          (<= (- 120 hue-minus-threshold)
                              h
                              (+ 120 hue-plus-threshold))
                          (>= s saturation-threshold)
                          (>= s value-treshold))
                 (idata:im-fast-set! out i j 0 r)
                 (idata:im-fast-set! out i j 1 g)
                 (idata:im-fast-set! out i j 2 b))))))
       out))))

(define (show-usage)
  (format (current-error-port)
          "Usage: extract-green-color.scm [OPTION]... input-file output-file
Extract green color from input-file and save to output-file.

Options:
  -r, --hue-red         hue threshold to express distance to red (default 60)
  -b, --hue-blue        hue threshold to express distance to blue (default 60)
  -s, --saturation      saturation threshold (default 0)
  -v, --value           value threshold (default 0)

  -h, --help            show this help
  -V, --version         show version information
"))

(define (show-version)
  (format (current-error-port)
          "extract-green-color.scm 2.0~%"))

(define (main args)
  (let* ((option-spec `((version (single-char #\V))
                        (help (single-char #\h))
                        (hue-red (single-char #\r) (value #t) (predicate ,string->number))
                        (hue-blue (single-char #\b) (value #t) (predicate ,string->number))
                        (saturation (single-char #\s) (value #t) (predicate ,string->number))
                        (value (single-char #\v) (value #t) (predicate ,string->number))))
         (options (getopt-long args option-spec)))
    (when (option-ref options 'help #f)
      (show-usage)
      (exit 1))
    (when (option-ref options 'version #f)
      (show-version)
      (exit 1))
    (unless (= 2 (length (option-ref options '() '())))
      (format (current-error-port) "extract-green-color.scm: non-option argument count must be 2~%")
      (show-usage)
      (exit 1))
    (match-let (((input-file output-file) (option-ref options '() '())))
      (im-save (extract-green-color (im-load input-file)
                                    (string->number (option-ref options 'hue-red "60"))
                                    (string->number (option-ref options 'hue-blue "60"))
                                    (string->number (option-ref options 'saturation "0.0"))
                                    (string->number (option-ref options 'value "0.0")))
               output-file))))