* blur.c: implement box blur; currently runs in O(n) but we could make it

O(1) trivially.

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2681 92316355-f0b4-4df1-b90c-862c8a59935f

pipi/filter/blur.c

@@ -85,3 +85,27 @@ pipi_image_t *pipi_gaussian_blur_ext(pipi_image_t *src, float rx, float ry,
     return ret;
 }
 
+/* FIXME: box blur would be incredibly faster using an accumulator instead
+ * of a convolution filter... */
+pipi_image_t *pipi_box_blur(pipi_image_t *src, int size)
+{
+    return pipi_box_blur_ext(src, size, size);
+}
+
+pipi_image_t *pipi_box_blur_ext(pipi_image_t *src, int m, int n)
+{
+    pipi_image_t *ret;
+    double *kernel;
+    int i;
+
+    kernel = malloc(m * n * sizeof(double));
+    for(i = 0; i < m * n; i++)
+        kernel[i] = 1. / (m * n);
+
+    ret = pipi_convolution(src, m, n, kernel);
+
+    free(kernel);
+
+    return ret;
+}
+

pipi/pipi.h

@@ -81,6 +81,8 @@ extern pipi_image_t *pipi_convolution(pipi_image_t *, int, int, double[]);
 extern pipi_image_t *pipi_gaussian_blur(pipi_image_t *, float);
 extern pipi_image_t *pipi_gaussian_blur_ext(pipi_image_t *,
                                             float, float, float, float);
+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 int pipi_flood_fill(pipi_image_t *,