Changeset 2715 for libpipi/trunk/pipi/filter/blur.cTweet

Timestamp:

Aug 14, 2008, 8:34:44 PM (15 years ago)

Author:

Sam Hocevar

Message:

• blur.c: add an argument to the gaussian convolution to specify an angle. Of course since the kernel is no longer separable, it becomes awfully slow with large images. Here is a tileable brushed metal texture: # pipi pipi:random512x512 --wrap --blur 20x0r25 -o image.png

File:

• libpipi/trunk/pipi/filter/blur.c (modified) (3 diffs)

libpipi/trunk/pipi/filter/blur.c

@@ -35 +35 @@
 pipi_image_t *pipi_gaussian_blur(pipi_image_t *src, float radius)
 {
-    return pipi_gaussian_blur_ext(src, radius, radius, 0.0, 0.0);
+    return pipi_gaussian_blur_ext(src, radius, radius, 0.0, 0.0, 0.0);
 }
 
 pipi_image_t *pipi_gaussian_blur_ext(pipi_image_t *src, float rx, float ry,
-                                     float dx, float dy)
+                                     float angle, float dx, float dy)
 {
     pipi_image_t *ret;
     double *kernel;
-    double Kx, Ky, t = 0.0;
+    double Kx, Ky, t = 0.0, sint, cost, bbx, bby;
     int i, j, krx, kry, m, n;
 
@@ -49 +49 @@
     if(ry < BLUR_EPSILON) ry = BLUR_EPSILON;
 
+    sint = sin(angle * M_PI / 180.);
+    cost = cos(angle * M_PI / 180.);
+
+    /* Compute the final ellipse's bounding box */
+    bbx = sqrt(rx * rx * cost * cost + ry * ry * sint * sint);
+    bby = sqrt(ry * ry * cost * cost + rx * rx * sint * sint);
+
     /* FIXME: the kernel becomes far too big with large values of dx, because
      * we grow both left and right. Fix the growing direction. */
-    krx = (int)(3. * rx + .99999 + ceil(abs(dx)));
+    krx = (int)(3. * bbx + .99999 + ceil(abs(dx)));
     m = 2 * krx + 1;
     Kx = -1. / (2. * rx * rx);
 
-    kry = (int)(3. * ry + .99999 + ceil(abs(dy)));
+    kry = (int)(3. * bby + .99999 + ceil(abs(dy)));
     n = 2 * kry + 1;
     Ky = -1. / (2. * ry * ry);
@@ -63 +70 @@
     for(j = -kry; j <= kry; j++)
     {
-        double ey = Ky * ((double)j + dy) * ((double)j + dy);
-
         for(i = -krx; i <= krx; i++)
         {
-            double ex = Kx * ((double)i + dx) * ((double)i + dx);
+            double u = (double)i * cost - (double)j * sint + dx;
+            double v = (double)j * cost + (double)i * sint + dy;
+            double ex = Kx * u * u;
+            double ey = Ky * v * v;
             double d = exp(ex + ey);