Re: get bounded box using cairo_stroke_extents
Lawrence D'Oliveiro <[email protected]>
| Newsgroups | gmane.comp.lib.cairo |
|---|---|
| Organization | Geek Central |
| Message-ID | <[email protected]> |
On Sat, 20 Feb 2016 23:52:30 -0700, Mark Olesen wrote:
> I am trying to get the bounded box using cairo_stroke_extents
> (cairo_fill_extents has similar issue). I wind up with x1 being
> way off. The rest look okay. I have attached a png. The blue
> rectangle is the bounds box. Any suggestions?
It makes more sense if you do cairo_restore before trying to get the
extents. Here is the patch I made, and attached is the patched source
and the PNG output.
diff -u stroke_extents.c{-orig,}
--- stroke_extents.c-orig 2016-02-22 11:53:06.963033270 +1300
+++ stroke_extents.c 2016-02-22 11:53:46.594795711 +1300
@@ -1,7 +1,8 @@
-#include <cairo.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
+#include <stdio.h>
+#include <cairo/cairo.h>
int
main (int argc, char *argv[])
@@ -37,10 +38,11 @@
cairo_translate(cr, -50., -20.); // *Lawrence D'Oliveiro tip*
cairo_set_source_rgb(cr, 0., 0., 0.);
cairo_stroke_extents(cr, &x1, &y1, &x2, &y2);
- cairo_stroke(cr);
+ printf("(%lf, %lf) (%lf,%lf)\n", x1, y1, x2, y2);
cairo_restore(cr);
-
+ cairo_stroke_extents(cr, &x1, &y1, &x2, &y2);
printf("(%lf, %lf) (%lf,%lf)\n", x1, y1, x2, y2);
+ cairo_stroke(cr);
/*
x1 is way off
(-1.500000, 19.500000) (151.500000,70.500000)
--
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skew.png
(image/png, 784 B) - not displayed
stroke_extents.c
(text/x-c++src, 1.4 KB)
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <cairo/cairo.h>
int
main (int argc, char *argv[])
{
cairo_surface_t* cs;
cairo_t *cr;
double angle;
double skewx;
cairo_matrix_t matrix;
double x1, x2, y1, y2;
cs= cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 180.,100.);
cr= cairo_create(cs);
cairo_set_line_width(cr, 1.);
cairo_save(cr);
cairo_set_source_rgb(cr, 1., 0., 0.);
cairo_rectangle(cr, 50., 20., 50., 50.);
cairo_stroke(cr);
cairo_restore(cr);
cairo_save(cr);
angle= 45.;
skewx= tan(angle * M_PI / 180.);
cairo_matrix_init(
&matrix,
1.0, 0.0,
skewx, 1.0,
50.0, 20.0);
cairo_transform(cr, &matrix);
cairo_rectangle(cr, 0., 0., 50., 50.);
cairo_translate(cr, -50., -20.); // *Lawrence D'Oliveiro tip*
cairo_set_source_rgb(cr, 0., 0., 0.);
cairo_stroke_extents(cr, &x1, &y1, &x2, &y2);
printf("(%lf, %lf) (%lf,%lf)\n", x1, y1, x2, y2);
cairo_restore(cr);
cairo_stroke_extents(cr, &x1, &y1, &x2, &y2);
printf("(%lf, %lf) (%lf,%lf)\n", x1, y1, x2, y2);
cairo_stroke(cr);
/*
x1 is way off
(-1.500000, 19.500000) (151.500000,70.500000)
*/
cairo_set_source_rgb(cr, 0., 0., 1.);
cairo_rectangle(cr, x1, y1, x2-x1, y2-y1);
cairo_stroke(cr);
cairo_surface_write_to_png(cs, "skew.png");
cairo_destroy(cr);
cairo_surface_destroy(cs);
return 0;
}