diff --git a/libgimpcolor/gimpcolor.def b/libgimpcolor/gimpcolor.def
index 3a3d02ec1a..494c6bf218 100644
--- a/libgimpcolor/gimpcolor.def
+++ b/libgimpcolor/gimpcolor.def
@@ -82,8 +82,6 @@ EXPORTS
 	gimp_rgb_composite
 	gimp_rgb_get_type
 	gimp_rgb_get_uchar
-	gimp_rgb_luminance
-	gimp_rgb_luminance_uchar
 	gimp_rgb_max
 	gimp_rgb_min
 	gimp_rgb_multiply
diff --git a/libgimpcolor/gimprgb.c b/libgimpcolor/gimprgb.c
index abe8b6e2af..e5fed9a7a4 100644
--- a/libgimpcolor/gimprgb.c
+++ b/libgimpcolor/gimprgb.c
@@ -197,42 +197,6 @@ gimp_rgb_clamp (GimpRGB *rgb)
   rgb->a = CLAMP (rgb->a, 0.0, 1.0);
 }
 
-/**
- * gimp_rgb_luminance:
- * @rgb: a #GimpRGB struct
- *
- * Returns: the luminous intensity of the range from 0.0 to 1.0.
- *
- * Since: 2.4
- **/
-gdouble
-gimp_rgb_luminance (const GimpRGB *rgb)
-{
-  gdouble luminance;
-
-  g_return_val_if_fail (rgb != NULL, 0.0);
-
-  luminance = GIMP_RGB_LUMINANCE (rgb->r, rgb->g, rgb->b);
-
-  return CLAMP (luminance, 0.0, 1.0);
-}
-
-/**
- * gimp_rgb_luminance_uchar:
- * @rgb: a #GimpRGB struct
- *
- * Returns: the luminous intensity in the range from 0 to 255.
- *
- * Since: 2.4
- **/
-guchar
-gimp_rgb_luminance_uchar (const GimpRGB *rgb)
-{
-  g_return_val_if_fail (rgb != NULL, 0);
-
-  return ROUND (gimp_rgb_luminance (rgb) * 255.0);
-}
-
 void
 gimp_rgb_composite (GimpRGB              *color1,
                     const GimpRGB        *color2,
diff --git a/libgimpcolor/gimprgb.h b/libgimpcolor/gimprgb.h
index ab502be195..0bf6eac995 100644
--- a/libgimpcolor/gimprgb.h
+++ b/libgimpcolor/gimprgb.h
@@ -78,9 +78,6 @@ gdouble   gimp_rgb_max             (const GimpRGB *rgb);
 gdouble   gimp_rgb_min             (const GimpRGB *rgb);
 void      gimp_rgb_clamp           (GimpRGB       *rgb);
 
-gdouble   gimp_rgb_luminance       (const GimpRGB *rgb);
-guchar    gimp_rgb_luminance_uchar (const GimpRGB *rgb);
-
 void      gimp_rgb_composite       (GimpRGB              *color1,
                                     const GimpRGB        *color2,
                                     GimpRGBCompositeMode  mode);
diff --git a/plug-ins/common/checkerboard.c b/plug-ins/common/checkerboard.c
index 52af2b1a3e..2ba3acd3f9 100644
--- a/plug-ins/common/checkerboard.c
+++ b/plug-ins/common/checkerboard.c
@@ -258,7 +258,10 @@ do_checkerboard_pattern (GObject      *config,
 {
   CheckerboardParam_t  param;
   GeglColor           *color;
-  GimpRGB              fg, bg;
+  guchar               fg[4]     = {0, 0, 0, 0};
+  guchar               bg[4]     = {0, 0, 0, 0};
+  guchar               fg_lum[1] = {0};
+  guchar               bg_lum[1] = {0};
   const Babl          *format;
   gint                 bpp;
   gboolean             mode = FALSE;
@@ -271,38 +274,40 @@ do_checkerboard_pattern (GObject      *config,
                   NULL);
 
   color = gimp_context_get_background ();
-  gegl_color_get_pixel (color, babl_format_with_space ("R'G'B'A double", NULL), &bg);
+  gegl_color_get_pixel (color, babl_format_with_space ("R'G'B'A u8", NULL), bg);
+  gegl_color_get_pixel (color, babl_format_with_space ("Y' u8", NULL), bg_lum);
   g_object_unref (color);
   color = gimp_context_get_foreground ();
-  gegl_color_get_pixel (color, babl_format_with_space ("R'G'B'A double", NULL), &fg);
+  gegl_color_get_pixel (color, babl_format_with_space ("R'G'B'A u8", NULL), fg);
+  gegl_color_get_pixel (color, babl_format_with_space ("Y' u8", NULL), fg_lum);
   g_object_unref (color);
 
   if (gimp_drawable_is_gray (drawable))
     {
-      param.bg[0] = gimp_rgb_luminance_uchar (&bg);
-      gimp_rgba_get_uchar (&bg, NULL, NULL, NULL, param.bg + 1);
+      param.bg[0] = bg_lum[0];
+      param.bg[1] = bg[3];
 
-      param.fg[0] = gimp_rgb_luminance_uchar (&fg);
-      gimp_rgba_get_uchar (&fg, NULL, NULL, NULL, param.fg + 3);
-
-      if (gimp_drawable_has_alpha (drawable))
-        format = babl_format ("R'G'B'A u8");
-      else
-        format = babl_format ("R'G'B' u8");
-    }
-  else
-    {
-      gimp_rgba_get_uchar (&bg,
-                           param.bg, param.bg + 1, param.bg + 2, param.bg + 1);
-
-      gimp_rgba_get_uchar (&fg,
-                           param.fg, param.fg + 1, param.fg + 2, param.fg + 3);
+      param.fg[0] = fg_lum[0];
+      param.fg[1] = fg[3];
 
       if (gimp_drawable_has_alpha (drawable))
         format = babl_format ("Y'A u8");
       else
         format = babl_format ("Y' u8");
     }
+  else
+    {
+      for (gint i = 0; i < 4; i++)
+        {
+          param.bg[i] = bg[i];
+          param.fg[i] = fg[i];
+        }
+
+      if (gimp_drawable_has_alpha (drawable))
+        format = babl_format ("R'G'B'A u8");
+      else
+        format = babl_format ("R'G'B' u8");
+    }
 
   bpp = babl_format_get_bytes_per_pixel (format);
 
diff --git a/plug-ins/gradient-flare/gradient-flare.c b/plug-ins/gradient-flare/gradient-flare.c
index 201667eb07..7bd436ad40 100644
--- a/plug-ins/gradient-flare/gradient-flare.c
+++ b/plug-ins/gradient-flare/gradient-flare.c
@@ -1258,7 +1258,9 @@ plugin_put_pixel_func (gint      ix,
     }
   else
     {
-      dest[0] = gimp_rgb_luminance_uchar (color);
+      guchar rgb[3] = {color->r * 255, color->g * 255, color->b * 255};
+
+      dest[0] = GIMP_RGB_LUMINANCE (rgb[0], rgb[1], rgb[2]);
     }
 
   if (dinfo.has_alpha)