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;;; R7RS-PNM --- Library for reading and writing PNM (Portable Any Map) files for R7RS
;;; Copyright © 2024 Masaya Tojo <masaya@tojo.tokyo>
;;;
;;; This file is part of R7RS-PNM.
;;;
;;; R7RS-PNM is free software: you can redistribute it and/or modify it
;;; under the terms of the GNU Lesser General Public License as published
;;; by the Free Software Foundation, either version 3 of the License, or
;;; (at your option) any later version.
;;;
;;; R7RS-PNM 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 Lesser General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public License
;;; along with R7RS-PNM. If not, see <https://www.gnu.org/licenses/>.
(define-library (pnm ppm)
(export make-ppm-image
%make-ppm-image)
(import (scheme base)
(scheme case-lambda)
(pnm image))
(begin
(define (make-ppm-image width height maxval)
(when (or (< maxval 0)
(< 65536 maxval))
(error "(pnm ppm) make-ppm-image: Maxval is out of range"))
(let ((data (make-bytevector (* width
height
(if (< maxval 256)
3
6))
0)))
(%make-ppm-image width height maxval data)))
(define (%make-ppm-image width height maxval data)
(when (or (< maxval 0)
(< 65536 maxval))
(error "(pnm ppm) make-ppm-image: Maxval is out of range"))
(if (< maxval 256)
(let* ((w*3 (* width 3))
(byte-count (* w*3 height)))
(define (xy->idx x y) (+ (* 3 x) (* y w*3)))
(define (pixel-getter x y)
(let ((idx (xy->idx x y)))
(values (bytevector-u8-ref data idx)
(bytevector-u8-ref data (+ idx 1))
(bytevector-u8-ref data (+ idx 2)))))
(define (pixel-setter x y r g b)
(let ((idx (xy->idx x y)))
(bytevector-u8-set! data idx r)
(bytevector-u8-set! data (+ idx 1) g)
(bytevector-u8-set! data (+ idx 2) b)))
(unless (= byte-count (bytevector-length data))
(error (string-append "(pnm pbm) make-pbm-image: Invalid bytevector length" byte-count)))
(make-image 'ppm width height maxval data pixel-getter pixel-setter))
(let* ((w*6 (* width 6))
(byte-count (* w*6 height)))
(define (xy->idx x y) (+ (* 6 x) (* y w*6)))
(define (pixel-getter x y)
(let ((idx (xy->idx x y)))
(values (combine-values (bytevector-u8-ref data idx)
(bytevector-u8-ref data (+ idx 1)))
(combine-values (bytevector-u8-ref data (+ idx 2))
(bytevector-u8-ref data (+ idx 3)))
(combine-values (bytevector-u8-ref data (+ idx 4))
(bytevector-u8-ref data (+ idx 5))))))
(define (pixel-setter x y r g b)
(let ((idx (xy->idx x y)))
(let-values (((r1 r2) (split-value r))
((g1 g2) (split-value g))
((b1 b2) (split-value b)))
(bytevector-u8-set! data idx r1)
(bytevector-u8-set! data (+ idx 1) r2)
(bytevector-u8-set! data (+ idx 2) g1)
(bytevector-u8-set! data (+ idx 3) g2)
(bytevector-u8-set! data (+ idx 4) b1)
(bytevector-u8-set! data (+ idx 5) b2))))
(unless (= byte-count (bytevector-length data))
(error (string-append "(pnm pbm) make-pbm-image: Invalid bytevector length" byte-count)))
(make-image 'ppm width height maxval data pixel-getter pixel-setter))))
(define (split-value v)
(values (modulo (quotient v 256) 256)
(modulo v 256)))
(define (combine-values l r)
(+ (* 256 l) r))))
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