1 files changed, 70 insertions, 0 deletions
diff --git a/image-format/pnm/pbm.scm b/image-format/pnm/pbm.scm
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+++ b/image-format/pnm/pbm.scm
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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 (image-format pnm pbm)
+  (export make-pbm-image
+          %make-pbm-image)
+  (import (scheme base)
+          (scheme case-lambda)
+          (image-format pnm image)
+          (image-format pnm private checker)
+          (image-format pnm private bitwise))
+  (begin
+    (define make-pbm-image
+      (case-lambda
+        ((width height)
+         (make-pbm-image width height #f))
+        ((width height unsafe?)
+         (let* ((byte-width (ceiling (/ width 8)))
+                (byte-count (* byte-width height))
+                (data (make-bytevector byte-count 0)))
+           (%make-pbm-image width height data unsafe?)))))
+
+    (define (%make-pbm-image width height data unsafe?)
+      (let* ((byte-width (ceiling (/ width 8)))
+             (byte-count (* byte-width height)))
+        (define (xy->byte-idx+bit-idx x y)
+          (let-values (((byte-x bit-x) (floor/ x 8)))
+            (values (+ (* y byte-width)
+                       byte-x)
+                    bit-x)))
+        (define (pixel-getter x y)
+          (let-values (((byte-idx bit-idx) (xy->byte-idx+bit-idx x y)))
+            (let ((byte (bytevector-u8-ref data byte-idx)))
+              (bit-set? (- 7 bit-idx) byte))))
+        (define (pixel-setter x y b)
+          (let-values (((byte-idx bit-idx) (xy->byte-idx+bit-idx x y)))
+            (let ((byte (bytevector-u8-ref data byte-idx)))
+              (bytevector-u8-set! data byte-idx
+                                  (copy-bit (- 7 bit-idx) byte b)))))
+        (unless (= byte-count (bytevector-length data))
+          (error (string-append "(image-format pnm pbm) make-pbm-image: Invalid bytevector length" byte-count)))
+        (let ((check-xy (make-xy-checker width height))
+              (check-boolean-value (make-boolean-value-checker)))
+          (make-pnm-image 'pbm width height #t data
+                          (if unsafe?
+                              pixel-getter
+                              (lambda (x y)
+                                (check-xy x y)
+                                (pixel-getter x y)))
+                          (if unsafe?
+                              pixel-setter
+                              (lambda (x y v)
+                                (check-xy x y)
+                                (check-boolean-value v)
+                                (pixel-setter x y v)))))))))