diff --git a/pipi/Makefile.am b/pipi/Makefile.am
index 621135d..c0a8450 100644
--- a/pipi/Makefile.am
+++ b/pipi/Makefile.am
@@ -41,7 +41,8 @@ codec_sources =
# Submodules
combine_sources = \
combine/mean.c \
- combine/minmax.c
+ combine/minmax.c \
+ combine/subadd.c
filter_sources = \
filter/autocontrast.c \
diff --git a/pipi/combine/subadd.c b/pipi/combine/subadd.c
new file mode 100644
index 0000000..5496535
--- /dev/null
+++ b/pipi/combine/subadd.c
@@ -0,0 +1,122 @@
+/*
+ * 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.
+ */
+
+/*
+ * subadd.c: sub and add computation functions
+ */
+
+#include "config.h"
+#include "common.h"
+
+#include "pipi.h"
+#include "pipi_internals.h"
+
+pipi_image_t *pipi_sub(pipi_image_t *img1, pipi_image_t *img2)
+{
+ pipi_image_t *dst;
+ pipi_pixels_t *img1p, *img2p, *dstp;
+ float *img1data, *img2data, *dstdata;
+ int x, y, w, h;
+
+ if(img1->w != img2->w || img1->h != img2->h)
+ return NULL;
+
+ w = img1->w;
+ h = img1->h;
+
+ dst = pipi_new(w, h);
+ dstp = pipi_getpixels(dst, PIPI_PIXELS_RGBA_F);
+ dstdata = (float *)dstp->pixels;
+
+ img1p = pipi_getpixels(img1, PIPI_PIXELS_RGBA_F);
+ img1data = (float *)img1p->pixels;
+ img2p = pipi_getpixels(img2, PIPI_PIXELS_RGBA_F);
+ img2data = (float *)img2p->pixels;
+
+ for(y = 0; y < h; y++)
+ {
+ for(x = 0; x < w; x++)
+ {
+ float p, q;
+
+ p = img1data[4 * (y * w + x)];
+ q = img2data[4 * (y * w + x)];
+ dstdata[4 * (y * w + x)] = p < q ? 0 : p - q;
+
+ p = img1data[4 * (y * w + x) + 1];
+ q = img2data[4 * (y * w + x) + 1];
+ dstdata[4 * (y * w + x) + 1] = p < q ? 0 : p - q;
+
+ p = img1data[4 * (y * w + x) + 2];
+ q = img2data[4 * (y * w + x) + 2];
+ dstdata[4 * (y * w + x) + 2] = p < q ? 0 : p - q;
+
+ p = img1data[4 * (y * w + x) + 3];
+ q = img2data[4 * (y * w + x) + 3];
+ dstdata[4 * (y * w + x) + 3] = p < q ? 0 : p - q;
+ }
+ }
+
+ return dst;
+}
+
+pipi_image_t *pipi_add(pipi_image_t *img1, pipi_image_t *img2)
+{
+ pipi_image_t *dst;
+ pipi_pixels_t *img1p, *img2p, *dstp;
+ float *img1data, *img2data, *dstdata;
+ int x, y, w, h;
+
+ if(img1->w != img2->w || img1->h != img2->h)
+ return NULL;
+
+ w = img1->w;
+ h = img1->h;
+
+ dst = pipi_new(w, h);
+ dstp = pipi_getpixels(dst, PIPI_PIXELS_RGBA_F);
+ dstdata = (float *)dstp->pixels;
+
+ img1p = pipi_getpixels(img1, PIPI_PIXELS_RGBA_F);
+ img1data = (float *)img1p->pixels;
+ img2p = pipi_getpixels(img2, PIPI_PIXELS_RGBA_F);
+ img2data = (float *)img2p->pixels;
+
+ for(y = 0; y < h; y++)
+ {
+ for(x = 0; x < w; x++)
+ {
+ float p, q;
+
+ p = img1data[4 * (y * w + x)];
+ q = img2data[4 * (y * w + x)];
+ dstdata[4 * (y * w + x)] = (p + q < 1.) ? p + q : 1.;
+
+ p = img1data[4 * (y * w + x) + 1];
+ q = img2data[4 * (y * w + x) + 1];
+ dstdata[4 * (y * w + x) + 1] = (p + q < 1.) ? p + q : 1.;
+
+ p = img1data[4 * (y * w + x) + 2];
+ q = img2data[4 * (y * w + x) + 2];
+ dstdata[4 * (y * w + x) + 2] = (p + q < 1.) ? p + q : 1.;
+
+ p = img1data[4 * (y * w + x) + 3];
+ q = img2data[4 * (y * w + x) + 3];
+ dstdata[4 * (y * w + x) + 3] = (p + q < 1.) ? p + q : 1.;
+ }
+ }
+
+ return dst;
+}
+
diff --git a/pipi/context.c b/pipi/context.c
index 7e273a1..e822f1a 100644
--- a/pipi/context.c
+++ b/pipi/context.c
@@ -146,6 +146,36 @@ int pipi_command(pipi_context_t *ctx, char const *cmd, ...)
ctx->images[ctx->nimages - 2] = dst;
ctx->nimages--;
}
+ else if(!strcmp(cmd, "sub"))
+ {
+ pipi_image_t *dst;
+
+ if(ctx->nimages < 2)
+ return -1;
+ dst = pipi_sub(ctx->images[ctx->nimages - 2],
+ ctx->images[ctx->nimages - 1]);
+ if(dst == NULL)
+ return -1;
+ pipi_free(ctx->images[ctx->nimages - 2]);
+ pipi_free(ctx->images[ctx->nimages - 1]);
+ ctx->images[ctx->nimages - 2] = dst;
+ ctx->nimages--;
+ }
+ else if(!strcmp(cmd, "add"))
+ {
+ pipi_image_t *dst;
+
+ if(ctx->nimages < 2)
+ return -1;
+ dst = pipi_add(ctx->images[ctx->nimages - 2],
+ ctx->images[ctx->nimages - 1]);
+ if(dst == NULL)
+ return -1;
+ pipi_free(ctx->images[ctx->nimages - 2]);
+ pipi_free(ctx->images[ctx->nimages - 1]);
+ ctx->images[ctx->nimages - 2] = dst;
+ ctx->nimages--;
+ }
else if(!strcmp(cmd, "min"))
{
pipi_image_t *dst;
diff --git a/pipi/pipi.h b/pipi/pipi.h
index a9ccc91..7f5a375 100644
--- a/pipi/pipi.h
+++ b/pipi/pipi.h
@@ -88,6 +88,8 @@ extern pipi_image_t *pipi_resize(pipi_image_t *, int, int);
extern pipi_image_t *pipi_mean(pipi_image_t *, pipi_image_t *);
extern pipi_image_t *pipi_min(pipi_image_t *, pipi_image_t *);
extern pipi_image_t *pipi_max(pipi_image_t *, pipi_image_t *);
+extern pipi_image_t *pipi_sub(pipi_image_t *, pipi_image_t *);
+extern pipi_image_t *pipi_add(pipi_image_t *, pipi_image_t *);
extern pipi_image_t *pipi_convolution(pipi_image_t *, int, int, double[]);
extern pipi_image_t *pipi_gaussian_blur(pipi_image_t *, float);
diff --git a/src/pipi.c b/src/pipi.c
index 26e22a6..d2463dd 100644
--- a/src/pipi.c
+++ b/src/pipi.c
@@ -66,6 +66,16 @@ int main(int argc, char *argv[])
if(pipi_command(ctx, "max") != 0)
return EXIT_FAILURE;
}
+ else if(!strcmp(argv[0], "--sub"))
+ {
+ if(pipi_command(ctx, "sub") != 0)
+ return EXIT_FAILURE;
+ }
+ else if(!strcmp(argv[0], "--add"))
+ {
+ if(pipi_command(ctx, "add") != 0)
+ return EXIT_FAILURE;
+ }
else if(!strcmp(argv[0], "--output") || !strcmp(argv[0], "-o"))
{
if(argv[1] == NULL)