diff --git a/pipi/combine/rgb.c b/pipi/combine/rgb.c
index 4f00725..1d1553d 100644
--- a/pipi/combine/rgb.c
+++ b/pipi/combine/rgb.c
@@ -60,3 +60,75 @@ pipi_image_t *pipi_rgb(pipi_image_t *i1, pipi_image_t *i2, pipi_image_t *i3)
     return dst;
 }
 
+pipi_image_t *pipi_red(pipi_image_t *src)
+{
+    pipi_image_t *dst;
+    pipi_pixels_t *srcp, *dstp;
+    float *srcdata, *dstdata;
+    int x, y, w, h;
+
+    w = src->w;
+    h = src->h;
+
+    dst = pipi_new(w, h);
+    dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F);
+    dstdata = (float *)dstp->pixels;
+
+    srcp = pipi_getpixels(src, PIPI_PIXELS_RGBA_F);
+    srcdata = (float *)srcp->pixels;
+
+    for(y = 0; y < h; y++)
+        for(x = 0; x < w; x++)
+            dstdata[y * w + x] = srcdata[4 * (y * w + x)];
+
+    return dst;
+}
+
+pipi_image_t *pipi_green(pipi_image_t *src)
+{
+    pipi_image_t *dst;
+    pipi_pixels_t *srcp, *dstp;
+    float *srcdata, *dstdata;
+    int x, y, w, h;
+
+    w = src->w;
+    h = src->h;
+
+    dst = pipi_new(w, h);
+    dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F);
+    dstdata = (float *)dstp->pixels;
+
+    srcp = pipi_getpixels(src, PIPI_PIXELS_RGBA_F);
+    srcdata = (float *)srcp->pixels;
+
+    for(y = 0; y < h; y++)
+        for(x = 0; x < w; x++)
+            dstdata[y * w + x] = srcdata[4 * (y * w + x) + 1];
+
+    return dst;
+}
+
+pipi_image_t *pipi_blue(pipi_image_t *src)
+{
+    pipi_image_t *dst;
+    pipi_pixels_t *srcp, *dstp;
+    float *srcdata, *dstdata;
+    int x, y, w, h;
+
+    w = src->w;
+    h = src->h;
+
+    dst = pipi_new(w, h);
+    dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F);
+    dstdata = (float *)dstp->pixels;
+
+    srcp = pipi_getpixels(src, PIPI_PIXELS_RGBA_F);
+    srcdata = (float *)srcp->pixels;
+
+    for(y = 0; y < h; y++)
+        for(x = 0; x < w; x++)
+            dstdata[y * w + x] = srcdata[4 * (y * w + x) + 2];
+
+    return dst;
+}
+
diff --git a/pipi/pipi.h b/pipi/pipi.h
index 41fd07a..840b6ab 100644
--- a/pipi/pipi.h
+++ b/pipi/pipi.h
@@ -106,6 +106,9 @@ extern double pipi_measure_rmsd(pipi_image_t *, pipi_image_t *);
 extern pipi_image_t *pipi_resize(pipi_image_t *, int, int);
 
 extern pipi_image_t *pipi_rgb(pipi_image_t *, pipi_image_t *, pipi_image_t *);
+extern pipi_image_t *pipi_red(pipi_image_t *);
+extern pipi_image_t *pipi_green(pipi_image_t *);
+extern pipi_image_t *pipi_blue(pipi_image_t *);
 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 *);