diff --git a/pipi/Makefile.am b/pipi/Makefile.am
index 76483c3..8367dd6 100644
--- a/pipi/Makefile.am
+++ b/pipi/Makefile.am
@@ -52,8 +52,8 @@ combine_sources = \
 filter_sources = \
 	filter/autocontrast.c \
 	filter/blur.c \
-	filter/convolution.c \
-	filter/convolution.h
+	filter/convolution.c filter/convolution_template.h \
+	filter/color.c
 
 dither_sources = \
 	dither/floydsteinberg.c \
diff --git a/pipi/context.c b/pipi/context.c
index 90ced40..3450fb5 100644
--- a/pipi/context.c
+++ b/pipi/context.c
@@ -383,6 +383,15 @@ int pipi_command(pipi_context_t *ctx, char const *cmd, ...)
         ctx->images[ctx->nimages - 1] = pipi_autocontrast(tmp);
         pipi_free(tmp);
     }
+    else if(!strcmp(cmd, "invert"))
+    {
+        pipi_image_t *tmp;
+        if(ctx->nimages < 1)
+            return -1;
+        tmp = ctx->images[ctx->nimages - 1];
+        ctx->images[ctx->nimages - 1] = pipi_invert(tmp);
+        pipi_free(tmp);
+    }
     else if(!strcmp(cmd, "gray"))
     {
         if(ctx->nimages < 1)
diff --git a/pipi/filter/color.c b/pipi/filter/color.c
new file mode 100644
index 0000000..cc16e5e
--- /dev/null
+++ b/pipi/filter/color.c
@@ -0,0 +1,73 @@
+/*
+ *  libpipi       Proper image processing implementation library
+ *  Copyright (c) 2004-2008 Sam Hocevar <sam@zoy.org>
+ *                All Rights Reserved
+ *
+ *  $Id$
+ *
+ *  This library is free software. It comes without any warranty, to
+ *  the extent permitted by applicable law. You can redistribute it
+ *  and/or modify it under the terms of the Do What The Fuck You Want
+ *  To Public License, Version 2, as published by Sam Hocevar. See
+ *  http://sam.zoy.org/wtfpl/COPYING for more details.
+ */
+
+/*
+ * color.c: colour manipulation functions
+ */
+
+#include "config.h"
+#include "common.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+#include "pipi.h"
+#include "pipi_internals.h"
+
+pipi_image_t *pipi_invert(pipi_image_t *src)
+{
+    pipi_image_t *dst;
+    pipi_pixels_t *srcp, *dstp;
+    float *srcdata, *dstdata;
+    int x, y, w, h, gray;
+
+    w = src->w;
+    h = src->h;
+
+    gray = (src->last_modified == PIPI_PIXELS_Y_F);
+
+    srcp = gray ? pipi_getpixels(src, PIPI_PIXELS_Y_F)
+                : pipi_getpixels(src, PIPI_PIXELS_RGBA_F);
+    srcdata = (float *)srcp->pixels;
+
+    dst = pipi_new(w, h);
+    dstp = gray ? pipi_getpixels(dst, PIPI_PIXELS_Y_F)
+                : pipi_getpixels(dst, PIPI_PIXELS_RGBA_F);
+    dstdata = (float *)dstp->pixels;
+
+    for(y = 0; y < h; y++)
+    {
+        for(x = 0; x < w; x++)
+        {
+            if(gray)
+            {
+                dstdata[y * w + x] = 1. - srcdata[y * w + x];
+            }
+            else
+            {
+                int d = 4 * (y * w + x);
+
+                dstdata[d] = 1. - srcdata[d];
+                dstdata[d + 1] = 1. - srcdata[d + 1];
+                dstdata[d + 2] = 1. - srcdata[d + 2];
+                dstdata[d + 3] = 1. - srcdata[d + 3];
+            }
+        }
+    }
+
+    return dst;
+}
+
diff --git a/pipi/pipi.h b/pipi/pipi.h
index 41dc361..5dc72aa 100644
--- a/pipi/pipi.h
+++ b/pipi/pipi.h
@@ -103,6 +103,7 @@ extern pipi_image_t *pipi_gaussian_blur_ext(pipi_image_t *,
 extern pipi_image_t *pipi_box_blur(pipi_image_t *, int);
 extern pipi_image_t *pipi_box_blur_ext(pipi_image_t *, int, int);
 extern pipi_image_t *pipi_autocontrast(pipi_image_t *);
+extern pipi_image_t *pipi_invert(pipi_image_t *);
 
 extern pipi_image_t *pipi_tile(pipi_image_t *, int, int);
 extern int pipi_flood_fill(pipi_image_t *,
diff --git a/src/pipi.c b/src/pipi.c
index 85c81a0..9ed9169 100644
--- a/src/pipi.c
+++ b/src/pipi.c
@@ -75,6 +75,11 @@ int main(int argc, char *argv[])
             if(pipi_command(ctx, "autocontrast") != 0)
                 return EXIT_FAILURE;
         }
+        else if(!strcmp(argv[0], "--invert"))
+        {
+            if(pipi_command(ctx, "invert") != 0)
+                return EXIT_FAILURE;
+        }
         else if(!strcmp(argv[0], "--wrap"))
         {
             if(pipi_command(ctx, "wrap") != 0)