Make `maxval` argument optional

2 files changed, 29 insertions, 21 deletions

diff --git a/pnm/pgm.scm b/pnm/pgm.scm
index 89f4c35..200720f 100644
--- a/pnm/pgm.scm
+++ b/pnm/pgm.scm
@@ -23,16 +23,20 @@
           (scheme case-lambda)
           (pnm image))
   (begin
-    (define (make-pgm-image width height maxval)
-      (when (or (< maxval 0)
-                (< 65536 maxval))
-        (error "(pnm pgm) make-pgm: maxval is out of range"))
-      (let* ((byte-count (* width height
-                            (if (< maxval 256)
-                                1
-                                2)))
-             (data (make-bytevector byte-count 0)))
-        (%make-pgm-image width height maxval data)))
+    (define make-pgm-image
+      (case-lambda
+        ((width height)
+         (make-pgm-image width height 255))
+        ((width height maxval)
+         (when (or (< maxval 0)
+                   (< 65536 maxval))
+           (error "(pnm pgm) make-pgm: maxval is out of range"))
+         (let* ((byte-count (* width height
+                               (if (< maxval 256)
+                                   1
+                                   2)))
+                (data (make-bytevector byte-count 0)))
+           (%make-pgm-image width height maxval data)))))
 
     (define (%make-pgm-image width height maxval data)
       (when (or (< maxval 0)
diff --git a/pnm/ppm.scm b/pnm/ppm.scm
index 496eee1..11331af 100644
--- a/pnm/ppm.scm
+++ b/pnm/ppm.scm
@@ -23,17 +23,21 @@
           (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
+      (case-lambda
+        ((width height)
+         (make-ppm-image width height 255))
+        ((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)