1 files changed, 111 insertions, 0 deletions
diff --git a/image-format/pnm/ppm.scm b/image-format/pnm/ppm.scm
new file mode 100644
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+++ b/image-format/pnm/ppm.scm
@@ -0,0 +1,111 @@
+;;; 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 (image-format pnm ppm)
+  (export make-ppm-image
+          %make-ppm-image)
+  (import (scheme base)
+          (scheme case-lambda)
+          (image-format pnm image)
+          (image-format pnm private checker)
+          (image-format pnm private double-byte))
+  (begin
+    (define make-ppm-image
+      (case-lambda
+        ((width height)
+         (make-ppm-image width height 255))
+        ((width height maxval)
+         (make-ppm-image width height maxval #f))
+        ((width height maxval unsafe?)
+         (when (or (< maxval 0)
+                   (< 65536 maxval))
+           (error "(image-format 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 unsafe?)))))
+
+    (define (%make-ppm-image width height maxval data unsafe?)
+      (define (make-safe-pixel-getter pixel-getter)
+        (let ((check-xy (make-xy-checker width height)))
+          (lambda (x y)
+            (check-xy x y)
+            (pixel-getter x y))))
+      (define (make-safe-pixel-setter pixel-setter)
+        (let ((check-xy (make-xy-checker width height))
+              (check-value-r (make-value-checker maxval 'r))
+              (check-value-g (make-value-checker maxval 'g))
+              (check-value-b (make-value-checker maxval 'b)))
+          (lambda (x y r g b)
+            (check-xy x y)
+            (check-value-r r)
+            (check-value-g g)
+            (check-value-b b)
+            (pixel-setter x y r g b))))
+      (when (or (< maxval 0)
+                (< 65536 maxval))
+        (error "(image-format 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 "(image-format pnm pbm) make-pbm-image: Invalid bytevector length" byte-count)))
+            (make-pnm-image 'ppm width height maxval data
+                            (if unsafe? pixel-getter (make-safe-pixel-getter pixel-getter))
+                            (if unsafe? pixel-setter (make-safe-pixel-setter 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-bytes (bytevector-u8-ref data idx)
+                                       (bytevector-u8-ref data (+ idx 1)))
+                        (combine-bytes (bytevector-u8-ref data (+ idx 2))
+                                       (bytevector-u8-ref data (+ idx 3)))
+                        (combine-bytes (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-double-byte r))
+                             ((g1 g2) (split-double-byte g))
+                             ((b1 b2) (split-double-byte 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 "(image-format pnm pbm) make-pbm-image: Invalid bytevector length" byte-count)))
+            (make-pnm-image 'ppm width height maxval data
+                            (if unsafe? pixel-getter (make-safe-pixel-getter pixel-getter))
+                            (if unsafe? pixel-setter (make-safe-pixel-setter pixel-setter))))))))