From: Bill Spitzak <spit...@gmail.com>
If GNUPLOT_OUTPUT is set, 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
---
pixman/pixman-image.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/pixman/pixman-image.c b/pixman/pixman-image.c
index 1ff1a49..69743c4 100644
--- a/pixman/pixman-image.c
+++ b/pixman/pixman-image.c
@@ -531,6 +531,46 @@ compute_image_info (pixman_image_t *image)
image->common.flags = flags;
image->common.extended_format_code = code;
+/* If GNUPLOT_OUTPUT is set, 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
+ */
+/* #define GNUPLOT_OUTPUT 1 */
+#if GNUPLOT_OUTPUT
+ if ((flags & FAST_PATH_SEPARABLE_CONVOLUTION_FILTER) &&
image->common.filter_params) {
+ const pixman_fixed_t* p = image->common.filter_params;
+ int width = pixman_fixed_to_int(p[0]);
+ int samples = 1 << pixman_fixed_to_int(p[2]);
+ int x,y;
+ p += 4;
+ 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 * .5 + (y + .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
}
void
--
1.9.1
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