Fix for the colour balance filter on systems with signed chars.

Added function rgb_to_l for use when we just need the luminosity.

ChangeLog

@@ -1,3 +1,12 @@
+Sun Feb 14 22:16:16 1999  Tor Lillqvist  <tml@iki.fi>
+
+	* app/paint_funcs.c app/paint_funcs.h : New function rgb_to_l for
+ 	when we only want the luminosity.  (rgb_to_hls): Use "else if" for
+ 	case which can't be true if previous test succeeded.
+
+	* app/color_balance.c (struct _ColorBalanceDialog): use
+	lookup tables with unsigned values for the RGB components.
+
 Sun Feb 14 23:27:57 CET 1999 Marc Lehmann <pcg@goof.com>
 
         * docs/parasites.txt: Added some suggestions from Jay Cox.

app/base/color-balance.c

@@ -71,9 +71,9 @@ struct _ColorBalanceDialog
   double       magenta_green[3];
   double       yellow_blue[3];
 
-  char         r_lookup[255];
-  char         g_lookup[255];
-  char         b_lookup[255];
+  guchar       r_lookup[255];
+  guchar       g_lookup[255];
+  guchar       b_lookup[255];
 
   gint         preserve_luminosity;
   gint         preview;

app/color_balance.c

@@ -71,9 +71,9 @@ struct _ColorBalanceDialog
   double       magenta_green[3];
   double       yellow_blue[3];
 
-  char         r_lookup[255];
-  char         g_lookup[255];
-  char         b_lookup[255];
+  guchar       r_lookup[255];
+  guchar       g_lookup[255];
+  guchar       b_lookup[255];
 
   gint         preserve_luminosity;
   gint         preview;

app/paint-funcs/paint-funcs.c

@@ -5327,7 +5327,7 @@ rgb_to_hls (int *r,
 
       if (h < 0)
 	h += 255;
-      if (h > 255)
+      else if (h > 255)
 	h -= 255;
     }
 
@@ -5337,6 +5337,45 @@ rgb_to_hls (int *r,
 }
 
 
+/* Just compute the luminosity component. */
+int
+rgb_to_l (int red,
+	  int green,
+	  int blue)
+{
+  float h, l, s;
+  int min, max;
+  int delta;
+
+  if (red > green)
+    {
+      if (red > blue)
+	max = red;
+      else
+	max = blue;
+
+      if (green < blue)
+	min = green;
+      else
+	min = blue;
+    }
+  else
+    {
+      if (green > blue)
+	max = green;
+      else
+	max = blue;
+
+      if (red < blue)
+	min = red;
+      else
+	min = blue;
+    }
+
+  return (max + min) / 2.0;
+}
+
+
 static int
 hls_value (float n1,
 	   float n2,

app/paint-funcs/paint-funcs.h

@@ -571,6 +571,7 @@ void  combine_regions_replace             (PixelRegion *, PixelRegion *,
 void  rgb_to_hsv            (int *, int *, int *);
 void  hsv_to_rgb            (int *, int *, int *);
 void  rgb_to_hls            (int *, int *, int *);
+int   rgb_to_l              (int, int, int);
 void  hls_to_rgb            (int *, int *, int *);
 
 /* Opacities */

app/paint_funcs.c

@@ -5327,7 +5327,7 @@ rgb_to_hls (int *r,
 
       if (h < 0)
 	h += 255;
-      if (h > 255)
+      else if (h > 255)
 	h -= 255;
     }
 
@@ -5337,6 +5337,45 @@ rgb_to_hls (int *r,
 }
 
 
+/* Just compute the luminosity component. */
+int
+rgb_to_l (int red,
+	  int green,
+	  int blue)
+{
+  float h, l, s;
+  int min, max;
+  int delta;
+
+  if (red > green)
+    {
+      if (red > blue)
+	max = red;
+      else
+	max = blue;
+
+      if (green < blue)
+	min = green;
+      else
+	min = blue;
+    }
+  else
+    {
+      if (green > blue)
+	max = green;
+      else
+	max = blue;
+
+      if (red < blue)
+	min = red;
+      else
+	min = blue;
+    }
+
+  return (max + min) / 2.0;
+}
+
+
 static int
 hls_value (float n1,
 	   float n2,

app/paint_funcs.h

@@ -571,6 +571,7 @@ void  combine_regions_replace             (PixelRegion *, PixelRegion *,
 void  rgb_to_hsv            (int *, int *, int *);
 void  hsv_to_rgb            (int *, int *, int *);
 void  rgb_to_hls            (int *, int *, int *);
+int   rgb_to_l              (int, int, int);
 void  hls_to_rgb            (int *, int *, int *);
 
 /* Opacities */

app/tools/color_balance.c

@@ -71,9 +71,9 @@ struct _ColorBalanceDialog
   double       magenta_green[3];
   double       yellow_blue[3];
 
-  char         r_lookup[255];
-  char         g_lookup[255];
-  char         b_lookup[255];
+  guchar       r_lookup[255];
+  guchar       g_lookup[255];
+  guchar       b_lookup[255];
 
   gint         preserve_luminosity;
   gint         preview;

app/tools/gimpcolorbalancetool.c

@@ -71,9 +71,9 @@ struct _ColorBalanceDialog
   double       magenta_green[3];
   double       yellow_blue[3];
 
-  char         r_lookup[255];
-  char         g_lookup[255];
-  char         b_lookup[255];
+  guchar       r_lookup[255];
+  guchar       g_lookup[255];
+  guchar       b_lookup[255];
 
   gint         preserve_luminosity;
   gint         preview;