Make the noise blue

4 files changed, 63 insertions, 11 deletions

diff --git a/bluenoise.c b/bluenoise.c
index ed57192..54dd4a1 100644
--- a/bluenoise.c
+++ b/bluenoise.c
@@ -4,7 +4,7 @@
 
 #include "fft.h"
 
-#define N_SAMPLES 512
+#define N_SAMPLES 256
 
 #define K   ((2 * M_PI) / N_SAMPLES)
 
@@ -25,7 +25,8 @@ main ()
 {
     complex_t *noise = malloc (sizeof (complex_t) * N_SAMPLES * N_SAMPLES);
     int i, j;
-
+    double max, min;
+    
     for (i = 0; i < N_SAMPLES; ++i)
     {
 	for (j = 0; j < N_SAMPLES; ++j)
@@ -36,10 +37,45 @@ main ()
     }
 
     fft_2d (noise, N_SAMPLES);
-
+    
     shift_2d (noise, N_SAMPLES);
 
-    show_image (noise, N_SAMPLES);
+    max = noise[0].re;
+    min = noise[0].re;
+
+    for (i = 0; i < N_SAMPLES; ++i)
+    {
+	for (j = 0; j < N_SAMPLES; ++j)
+	{
+	    double d = sqrt ((i - N_SAMPLES/2) * (i - N_SAMPLES/2) +
+			     (j - N_SAMPLES/2) * (j - N_SAMPLES/2));
+	    double f = (d / (sqrt (2) * N_SAMPLES)); // * (d / N_SAMPLES);
+	    
+
+	    if (d != 0.0)
+	    {
+#if 0
+		noise[i * N_SAMPLES + j].re *= 0.5 * (cos (M_PI * (1 - 2 * f)) + 1.0);
+		noise[i * N_SAMPLES + j].im *= 0.5 * (cos (M_PI * (1 - 2 * f)) + 1.0);
+#endif
+		noise[i * N_SAMPLES + j].re *= f;
+		noise[i * N_SAMPLES + j].im *= f;
+	    }
+	}
+    }
+
+    printf ("%f %f\n", noise[i * (N_SAMPLES/2) + N_SAMPLES/2].re, noise[i * (N_SAMPLES/2) + N_SAMPLES/2].im);
+    
+#if 0
+    noise[i * (N_SAMPLES / 2) + N_SAMPLES / 2].re = 1.5;
+    noise[i * (N_SAMPLES / 2) + N_SAMPLES / 2].im = 0;
+#endif
+    
+    shift_2d (noise, N_SAMPLES);
+    
+    ifft_2d (noise, N_SAMPLES);
+    
+    show_image ("blue noise", noise, N_SAMPLES);
     
     return 0;
 }
diff --git a/fft.c b/fft.c
index 9a9682f..46215cb 100644
--- a/fft.c
+++ b/fft.c
@@ -90,9 +90,10 @@ shift (complex_t *buffer, int n)
     }
 }
 
+typedef void (* fft_1d_t) (complex_t *buffer, int n);
 
-void
-fft_2d (complex_t *buffer, int n)
+static void
+do_fft_2d (complex_t *buffer, int n, fft_1d_t func1d)
 {
     int i;
 
@@ -101,7 +102,7 @@ fft_2d (complex_t *buffer, int n)
     {
 	complex_t *b = buffer + i * n;
 
-	fft (b, n);
+	func1d (b, n);
     }
 
     /* Then the columns */
@@ -113,7 +114,7 @@ fft_2d (complex_t *buffer, int n)
 	for (j = 0; j < n; ++j)
 	    tmp[j] = buffer[j * n + i];
 
-	fft (tmp, n);
+	func1d (tmp, n);
 
 	for (j = 0; j < n; ++j)
 	    buffer[j * n + i] = tmp[j];
@@ -123,6 +124,18 @@ fft_2d (complex_t *buffer, int n)
 }
 
 void
+fft_2d (complex_t *buffer, int n)
+{
+    do_fft_2d (buffer, n, fft);
+}
+
+void
+ifft_2d (complex_t *buffer, int n)
+{
+    do_fft_2d (buffer, n, ifft);
+}
+
+void
 shift_2d (complex_t *buffer, int n)
 {
     int i, j;
diff --git a/fft.h b/fft.h
index d82a992..31d7667 100644
--- a/fft.h
+++ b/fft.h
@@ -74,6 +74,9 @@ ifft (complex_t *buffer, int n);
 void
 fft_2d (complex_t *buffer, int n);
 
+void
+ifft_2d (complex_t *buffer, int n);
+
 /* Shifts the zero component to the center of the array */
 void
 shift (complex_t *buffer, int n);
@@ -82,4 +85,4 @@ void
 shift_2d (complex_t *buffer, int n);
 
 void
-show_image (complex_t *image, int n);
+show_image (const char *name, complex_t *image, int n);
diff --git a/gtk-utils.c b/gtk-utils.c
index 39f697a..0e2c848 100644
--- a/gtk-utils.c
+++ b/gtk-utils.c
@@ -51,13 +51,13 @@ on_expose (GtkWidget *widget, GdkEventExpose *expose, gpointer data)
 }
 
 void
-show_image (complex_t *image, int n)
+show_image (const char *name, complex_t *image, int n)
 {
     GtkWidget *window;
     GdkPixbuf *pixbuf;
     int argc;
     char **argv;
-    char *arg0 = g_strdup ("pixman-test-program");
+    char *arg0 = g_strdup (name);
 
     argc = 1;
     argv = (char **)&arg0;