[Pixman] [PATCH v12 04/14] pixman-image: Added enable-gnuplot config to view filters in gnuplot

[spitzak at gmail.com]

From: Bill Spitzak <spitzak at gmail.com>

If enable-gnuplot is configured, then you can pipe the output of a pixman-using program
to gnuplot and get a continuously-updated plot of the horizontal filter. This
works well with demos/scale to test the filter generation.

The plot is all the different subposition filters shuffled together. This is
misleading in a few cases:

  IMPULSE.BOX - goes up and down as the subfilters have different numbers of non-zero samples
  IMPULSE.TRIANGLE - somewhat crooked for the same reason
  1-wide filters - looks triangular, but a 1-wide box would be more accurate

v7: First time this ability was included

v8: Use config option
    Moved code to the filter generator
    Modified scale demo to not call filter generator a second time.

v10: Only print if successful generation of plots
     Use #ifdef, not #if

v11: small whitespace fixes

Signed-off-by: Bill Spitzak <spitzak at gmail.com>
Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>
---
 configure.ac           | 13 +++++++++++++
 pixman/pixman-filter.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/configure.ac b/configure.ac
index 6b2134e..e833e45 100644
--- a/configure.ac
+++ b/configure.ac
@@ -834,6 +834,19 @@ fi
 AC_SUBST(PIXMAN_TIMERS)
 
 dnl ===================================
+dnl gnuplot
+
+AC_ARG_ENABLE(gnuplot,
+   [AC_HELP_STRING([--enable-gnuplot],
+                   [enable output of filters that can be piped to gnuplot [default=no]])],
+   [enable_gnuplot=$enableval], [enable_gnuplot=no])
+
+if test $enable_gnuplot = yes ; then
+   AC_DEFINE(PIXMAN_GNUPLOT, 1, [enable output that can be piped to gnuplot])
+fi
+AC_SUBST(PIXMAN_GNUPLOT)
+
+dnl ===================================
 dnl GTK+
 
 AC_ARG_ENABLE(gtk,
diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c
index b2bf53f..3981c8b 100644
--- a/pixman/pixman-filter.c
+++ b/pixman/pixman-filter.c
@@ -297,6 +297,47 @@ create_1d_filter (int             *width,
     return params;
 }
 
+#ifdef PIXMAN_GNUPLOT
+/* If enable-gnuplot is configured, then you can pipe the output of a
+ * pixman-using program to gnuplot and get a continuously-updated plot
+ * of the horizontal filter. This works well with demos/scale to test
+ * the filter generation.
+ *
+ * The plot is all the different subposition filters shuffled
+ * together. This is misleading in a few cases:
+ *
+ *  IMPULSE.BOX - goes up and down as the subfilters have different
+ *		  numbers of non-zero samples
+ *  IMPULSE.TRIANGLE - somewhat crooked for the same reason
+ *  1-wide filters - looks triangular, but a 1-wide box would be more
+ *		     accurate
+ */
+static void
+gnuplot_filter(int width, int samples, const pixman_fixed_t* p)
+{
+    int x,y;
+    printf("plot '-' with linespoints\n");
+    printf("%g 0\n", - width * .5);
+    for (x = 0; x < width; ++x) {
+	for (y = 0; y < samples; ++y) {
+	    int yy;
+	    if (width & 1)
+		yy = y;
+	    else if (y >= samples / 2)
+		yy = y - samples / 2;
+	    else
+		yy = samples / 2 + y;
+	    printf("%g %g\n",
+		   x - width * 0.5 + (y + 0.5) * (1.0 / samples),
+		   pixman_fixed_to_double(p[(yy + 1) * width - x - 1]));
+	}
+    }
+    printf("%g 0\n", width * .5);
+    printf("e\n");
+    fflush(stdout);
+}
+#endif
+
 /* Create the parameter list for a SEPARABLE_CONVOLUTION filter
  * with the given kernels and scale parameters
  */
@@ -342,6 +383,10 @@ pixman_filter_create_separable_convolution (int             *n_values,
     memcpy (params + 4 + width * subsample_x, vert,
 	    height * subsample_y * sizeof (pixman_fixed_t));
 
+#ifdef PIXMAN_GNUPLOT
+    gnuplot_filter(width, subsample_x, params+4);
+#endif
+
 out:
     free (horz);
     free (vert);
-- 
1.9.1