Package: libcaca0
Version: 0.99.beta17-1
Severity: normal
Running the foo.c below prints an ellipse like
*****
* *
* *
* *
* *
* *
*****
where I hoped it might look like
***
* *
* *
* *
* *
* *
***
which doesn't have the square corners top and bottom, and is symmetric
vertically and horizontally. Some other sizes have a few doubtful
looking pixels, but this is probably the most obvious.
Nosing around the code, it's possible the +3 from the computer graphics
book might be right. I think the step is supposed to maintain
d1 == (x+1)^2*b^2 + (y-1/2)^2*a^2 - a^2*b^2
or something like that, if chucking in a debug assertion helped. Does
+1 or +3 depend whether the x++ increment is before or after the d1
step, maybe?
Incidentally, in the d1>=0 case is "2*x*1" meant to be "2*x+1"?
#include <stdio.h>
#include <stdlib.h>
#include "caca.h"
int
main (void)
{
caca_canvas_t *c;
caca_display_t *d;
int size = 3;
int a = size;
int b = size;
int x = a;
int y = b;
d = caca_create_display(NULL);
if(!d) abort();
c = caca_get_canvas(d);
caca_draw_ellipse(c, x,y, a,b, '*');
caca_refresh_display(d);
caca_free_canvas(c);
caca_free_display(d);
return 0;
}
-- System Information:
Debian Release: squeeze/sid
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.32-5-486
Locale: LANG=en_AU, LC_CTYPE=en_AU (charmap=ISO-8859-1)
Shell: /bin/sh linked to /bin/dash
Versions of packages libcaca0 depends on:
ii libc6 2.11.1-3 Embedded GNU C Library: Shared lib
ii libgcc1 1:4.4.4-6 GCC support library
ii libncursesw5 5.7+20100313-3 shared libraries for terminal hand
ii libslang2 2.2.2-4 The S-Lang programming library - r
ii libstdc++6 4.4.4-6 The GNU Standard C++ Library v3
ii zlib1g 1:1.2.3.4.dfsg-3 compression library - runtime
libcaca0 recommends no packages.
libcaca0 suggests no packages.
-- no debconf information
