--- OLD/ppm/ppmquant.c	Thu Jan  1 00:00:00 1970
+++ NEW/ppm/ppmquant.c	Thu Jan  1 00:00:00 1970
@@ -31,10 +31,10 @@
     };
 
 static colorhist_vector mediancut ARGS(( colorhist_vector chv, int colors, int sum, pixval maxval, int newcolors ));
-static int redcompare ARGS(( colorhist_vector ch1, colorhist_vector ch2 ));
-static int greencompare ARGS(( colorhist_vector ch1, colorhist_vector ch2 ));
-static int bluecompare ARGS(( colorhist_vector ch1, colorhist_vector ch2 ));
-static int sumcompare ARGS(( box_vector b1, box_vector b2 ));
+static int redcompare ARGS((const void *, const void *));
+static int greencompare ARGS((const void *, const void *));
+static int bluecompare ARGS((const void *, const void *));
+static int sumcompare ARGS((const void *, const void *));
 
 int
 main( argc, argv )
@@ -590,30 +590,25 @@
     return colormap;
     }
 
-static int
-redcompare( ch1, ch2 )
-    colorhist_vector ch1, ch2;
+static int redcompare(const void *a1, const void *a2)
     {
-    return (int) PPM_GETR( ch1->color ) - (int) PPM_GETR( ch2->color );
+    return (int) PPM_GETR(((const struct colorhist_item *)a1)->color) -
+	   (int) PPM_GETR(((const struct colorhist_item *)a2)->color);
     }
 
-static int
-greencompare( ch1, ch2 )
-    colorhist_vector ch1, ch2;
+static int greencompare(const void *a1, const void *a2)
     {
-    return (int) PPM_GETG( ch1->color ) - (int) PPM_GETG( ch2->color );
+    return (int) PPM_GETG(((const struct colorhist_item *)a1)->color) -
+	   (int) PPM_GETG(((const struct colorhist_item *)a2)->color);
     }
 
-static int
-bluecompare( ch1, ch2 )
-    colorhist_vector ch1, ch2;
+static int bluecompare(const void *a1, const void *a2)
     {
-    return (int) PPM_GETB( ch1->color ) - (int) PPM_GETB( ch2->color );
+    return (int) PPM_GETB(((const struct colorhist_item *)a1)->color) -
+	   (int) PPM_GETB(((const struct colorhist_item *)a2)->color);
     }
 
-static int
-sumcompare( b1, b2 )
-    box_vector b1, b2;
+static int sumcompare(const void *a1, const void *a2)
     {
-    return b2->sum - b1->sum;
+    return ((const struct box *)a1)->sum - ((const struct box *)a2)->sum;
     }