From 5ed490cac58d9f548bc141cc334c25dea9bfcaf2 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sun, 9 Oct 2022 20:35:05 -0400
Subject: image: png: Add support for paletted images via auto-expansion.

---
 chickadee/image/png.scm | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/chickadee/image/png.scm b/chickadee/image/png.scm
index b6cb3bf..6cdbc14 100644
--- a/chickadee/image/png.scm
+++ b/chickadee/image/png.scm
@@ -36,7 +36,8 @@
 ;;; Enums
 ;;;
 
-(define PNG_TRANSFORM_IDENTITY 0)
+(define PNG_TRANSFORM_IDENTITY #x0000)
+(define PNG_TRANSFORM_EXPAND #x0010)
 
 (define PNG_COLOR_MASK_PALETTE 1)
 (define PNG_COLOR_MASK_COLOR 2)
@@ -185,7 +186,7 @@
 (define (read-png read-struct info-struct)
   (png-read-png (unwrap-png-read-struct read-struct)
                 (unwrap-png-info-struct info-struct)
-                PNG_TRANSFORM_IDENTITY
+                PNG_TRANSFORM_EXPAND
                 %null-pointer))
 
 (define (png-header? header)
@@ -247,8 +248,9 @@
                        (bytevector-u16-ref row offset
                                            (endianness big)))))
            (values gray gray gray 255))))))
+   ;; This case should hopefully not happen due to using the
+   ;; PNG_TRANSFORM_EXPAND read flag, but just in case...
    ((= color-type PNG_COLOR_TYPE_PALETTE)
-    ;; TODO: Handle palettes.
     (raise-exception
      (make-exception-with-message
       "PNG images using color palettes are not supported")))
-- 
cgit v1.2.3