diff --git a/wrlib/draw.c b/wrlib/draw.c
index 7f54c7a6..350837c6 100644
--- a/wrlib/draw.c
+++ b/wrlib/draw.c
@@ -61,7 +61,7 @@ Bool RGetPixel(RImage * image, int x, int y, RColor * color)
 	return True;
 }
 
-void RPutPixel(RImage * image, int x, int y, RColor * color)
+void RPutPixel(RImage *image, int x, int y, const RColor *color)
 {
 	unsigned char *ptr;
 
@@ -104,7 +104,7 @@ void RPutPixel(RImage * image, int x, int y, RColor * color)
 	}
 }
 
-static void operatePixel(RImage * image, int ofs, int operation, RColor * color)
+static void operatePixel(RImage * image, int ofs, int operation, const RColor * color)
 {
 	unsigned char *sr, *sg, *sb, *sa;
 	register int alpha, nalpha, tmp;
@@ -170,7 +170,7 @@ static void operatePixel(RImage * image, int ofs, int operation, RColor * color)
 	}
 }
 
-void ROperatePixel(RImage * image, int operation, int x, int y, RColor * color)
+void ROperatePixel(RImage * image, int operation, int x, int y, const RColor * color)
 {
 	int ofs;
 
@@ -184,7 +184,7 @@ void ROperatePixel(RImage * image, int operation, int x, int y, RColor * color)
 	operatePixel(image, ofs, operation, color);
 }
 
-void RPutPixels(RImage * image, RPoint * points, int npoints, int mode, RColor * color)
+void RPutPixels(RImage * image, const RPoint * points, int npoints, int mode, const RColor * color)
 {
 	register int x, y, i;
 
@@ -205,7 +205,7 @@ void RPutPixels(RImage * image, RPoint * points, int npoints, int mode, RColor *
 	}
 }
 
-void ROperatePixels(RImage * image, int operation, RPoint * points, int npoints, int mode, RColor * color)
+void ROperatePixels(RImage * image, int operation, const RPoint * points, int npoints, int mode, const RColor * color)
 {
 	register int x, y, i;
 
@@ -287,7 +287,7 @@ static Bool clipLineInRectangle(int xmin, int ymin, int xmax, int ymax, int *x1,
  * This routine is a generic drawing routine, based on Bresenham's line
  * drawing algorithm.
  */
-static int genericLine(RImage * image, int x0, int y0, int x1, int y1, RColor * color, int operation, int polyline)
+static int genericLine(RImage * image, int x0, int y0, int x1, int y1, const RColor * color, int operation, int polyline)
 {
 	int i, err, du, dv, du2, dv2, uofs, vofs, last;
 
@@ -377,17 +377,17 @@ static int genericLine(RImage * image, int x0, int y0, int x1, int y1, RColor *
 	return True;
 }
 
-int RDrawLine(RImage * image, int x0, int y0, int x1, int y1, RColor * color)
+int RDrawLine(RImage * image, int x0, int y0, int x1, int y1, const RColor * color)
 {
 	return genericLine(image, x0, y0, x1, y1, color, RNormalOperation, False);
 }
 
-int ROperateLine(RImage * image, int operation, int x0, int y0, int x1, int y1, RColor * color)
+int ROperateLine(RImage * image, int operation, int x0, int y0, int x1, int y1, const RColor * color)
 {
 	return genericLine(image, x0, y0, x1, y1, color, operation, False);
 }
 
-void RDrawLines(RImage * image, RPoint * points, int npoints, int mode, RColor * color)
+void RDrawLines(RImage * image, const RPoint * points, int npoints, int mode, const RColor * color)
 {
 	register int x1, y1, x2, y2, i;
 
@@ -425,7 +425,7 @@ void RDrawLines(RImage * image, RPoint * points, int npoints, int mode, RColor *
 	genericLine(image, x1, y1, x2, y2, color, RNormalOperation, i);
 }
 
-void ROperateLines(RImage * image, int operation, RPoint * points, int npoints, int mode, RColor * color)
+void ROperateLines(RImage * image, int operation, const RPoint * points, int npoints, int mode, const RColor * color)
 {
 	register int x1, y1, x2, y2, i;
 
@@ -463,7 +463,7 @@ void ROperateLines(RImage * image, int operation, RPoint * points, int npoints,
 	genericLine(image, x1, y1, x2, y2, color, operation, i);
 }
 
-void RDrawSegments(RImage * image, RSegment * segs, int nsegs, RColor * color)
+void RDrawSegments(RImage * image, const RSegment * segs, int nsegs, const RColor * color)
 {
 	register int i;
 
@@ -475,7 +475,7 @@ void RDrawSegments(RImage * image, RSegment * segs, int nsegs, RColor * color)
 	}
 }
 
-void ROperateSegments(RImage * image, int operation, RSegment * segs, int nsegs, RColor * color)
+void ROperateSegments(RImage * image, int operation, const RSegment * segs, int nsegs, const RColor * color)
 {
 	register int i;
 
diff --git a/wrlib/misc.c b/wrlib/misc.c
index bbebee3c..399aa6f3 100644
--- a/wrlib/misc.c
+++ b/wrlib/misc.c
@@ -80,7 +80,7 @@ void RBevelImage(RImage * image, int bevel_type)
 	}
 }
 
-void RFillImage(RImage * image, RColor * color)
+void RFillImage(RImage * image, const RColor * color)
 {
 	unsigned char *d = image->data;
 	unsigned lineSize;
@@ -110,7 +110,7 @@ void RFillImage(RImage * image, RColor * color)
 	}
 }
 
-void RClearImage(RImage * image, RColor * color)
+void RClearImage(RImage * image, const RColor * color)
 {
 	unsigned char *d = image->data;
 	unsigned lineSize;
diff --git a/wrlib/wraster.h b/wrlib/wraster.h
index 8a144e2d..f01f33d9 100644
--- a/wrlib/wraster.h
+++ b/wrlib/wraster.h
@@ -378,31 +378,31 @@ RImage* RMakeCenteredImage(RImage *image, unsigned width, unsigned height,
  */
 Bool RGetPixel(RImage *image, int x, int y, RColor *color);
 
-void RPutPixel(RImage *image, int x, int y, RColor *color);
+void RPutPixel(RImage *image, int x, int y, const RColor *color);
 
-void ROperatePixel(RImage *image, int operation, int x, int y, RColor *color);
+void ROperatePixel(RImage *image, int operation, int x, int y, const RColor *color);
 
-void RPutPixels(RImage *image, RPoint *points, int npoints, int mode,
-                RColor *color);
+void RPutPixels(RImage *image, const RPoint *points, int npoints, int mode,
+                const RColor *color);
 
-void ROperatePixels(RImage *image, int operation, RPoint *points,
-                    int npoints, int mode, RColor *color);
+void ROperatePixels(RImage *image, int operation, const RPoint *points,
+                    int npoints, int mode, const RColor *color);
 
-int RDrawLine(RImage *image, int x0, int y0, int x1, int y1, RColor *color);
+int RDrawLine(RImage *image, int x0, int y0, int x1, int y1, const RColor *color);
 
 int ROperateLine(RImage *image, int operation, int x0, int y0, int x1, int y1,
-                 RColor *color);
+                 const RColor *color);
 
-void RDrawLines(RImage *image, RPoint *points, int npoints, int mode,
-                RColor *color);
+void RDrawLines(RImage *image, const RPoint *points, int npoints, int mode,
+                const RColor *color);
 
-void ROperateLines(RImage *image, int operation, RPoint *points, int npoints,
-                   int mode, RColor *color);
+void ROperateLines(RImage *image, int operation, const RPoint *points, int npoints,
+                   int mode, const RColor *color);
 
-void RDrawSegments(RImage *image, RSegment *segs, int nsegs, RColor *color);
+void RDrawSegments(RImage *image, const RSegment *segs, int nsegs, const RColor *color);
 
-void ROperateSegments(RImage *image, int operation, RSegment *segs, int nsegs,
-                      RColor *color);
+void ROperateSegments(RImage *image, int operation, const RSegment *segs, int nsegs,
+                      const RColor *color);
 
 /*
  * Color convertion
@@ -413,11 +413,11 @@ void RHSVtoRGB(RHSVColor *hsv, RColor *rgb);
 /*
  * Painting
  */
-void RClearImage(RImage *image, RColor *color);
+void RClearImage(RImage *image, const RColor *color);
 
 void RLightImage(RImage *image, RColor *color);
 
-void RFillImage(RImage *image, RColor *color);
+void RFillImage(RImage *image, const RColor *color);
 
 void RBevelImage(RImage *image, int bevel_type);