diff --git a/libavfilter/drawutils.c b/libavfilter/drawutils.c
index dd9ceff117..bf308a1c5c 100644
--- a/libavfilter/drawutils.c
+++ b/libavfilter/drawutils.c
@@ -23,6 +23,21 @@
 
 enum { RED = 0, GREEN, BLUE, ALPHA };
 
+int ff_fill_rgba_map(uint8_t *rgba_map, enum PixelFormat pix_fmt)
+{
+    switch (pix_fmt) {
+    case PIX_FMT_ARGB:  rgba_map[ALPHA] = 0; rgba_map[RED  ] = 1; rgba_map[GREEN] = 2; rgba_map[BLUE ] = 3; break;
+    case PIX_FMT_ABGR:  rgba_map[ALPHA] = 0; rgba_map[BLUE ] = 1; rgba_map[GREEN] = 2; rgba_map[RED  ] = 3; break;
+    case PIX_FMT_RGBA:
+    case PIX_FMT_RGB24: rgba_map[RED  ] = 0; rgba_map[GREEN] = 1; rgba_map[BLUE ] = 2; rgba_map[ALPHA] = 3; break;
+    case PIX_FMT_BGRA:
+    case PIX_FMT_BGR24: rgba_map[BLUE ] = 0; rgba_map[GREEN] = 1; rgba_map[RED  ] = 2; rgba_map[ALPHA] = 3; break;
+    default:                    /* unsupported */
+        return AVERROR(EINVAL);
+    }
+    return 0;
+}
+
 int ff_fill_line_with_color(uint8_t *line[4], int pixel_step[4], int w, uint8_t dst_color[4],
                             enum PixelFormat pix_fmt, uint8_t rgba_color[4],
                             int *is_packed_rgba, uint8_t rgba_map_ptr[4])
@@ -32,17 +47,7 @@ int ff_fill_line_with_color(uint8_t *line[4], int pixel_step[4], int w, uint8_t
     const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[pix_fmt];
     int hsub = pix_desc->log2_chroma_w;
 
-    *is_packed_rgba = 1;
-    switch (pix_fmt) {
-    case PIX_FMT_ARGB:  rgba_map[ALPHA] = 0; rgba_map[RED  ] = 1; rgba_map[GREEN] = 2; rgba_map[BLUE ] = 3; break;
-    case PIX_FMT_ABGR:  rgba_map[ALPHA] = 0; rgba_map[BLUE ] = 1; rgba_map[GREEN] = 2; rgba_map[RED  ] = 3; break;
-    case PIX_FMT_RGBA:
-    case PIX_FMT_RGB24: rgba_map[RED  ] = 0; rgba_map[GREEN] = 1; rgba_map[BLUE ] = 2; rgba_map[ALPHA] = 3; break;
-    case PIX_FMT_BGRA:
-    case PIX_FMT_BGR24: rgba_map[BLUE ] = 0; rgba_map[GREEN] = 1; rgba_map[RED  ] = 2; rgba_map[ALPHA] = 3; break;
-    default:
-        *is_packed_rgba = 0;
-    }
+    *is_packed_rgba = ff_fill_rgba_map(rgba_map, pix_fmt) >= 0;
 
     if (*is_packed_rgba) {
         pixel_step[0] = (av_get_bits_per_pixel(pix_desc))>>3;
diff --git a/libavfilter/drawutils.h b/libavfilter/drawutils.h
index e838660579..330b1cb0aa 100644
--- a/libavfilter/drawutils.h
+++ b/libavfilter/drawutils.h
@@ -27,6 +27,8 @@
 #include <stdint.h>
 #include "libavutil/pixfmt.h"
 
+int ff_fill_rgba_map(uint8_t *rgba_map, enum PixelFormat pix_fmt);
+
 int ff_fill_line_with_color(uint8_t *line[4], int pixel_step[4], int w,
                             uint8_t dst_color[4],
                             enum PixelFormat pix_fmt, uint8_t rgba_color[4],