[cairo] plots of contiguous rectangles
Carl Worth
cworth at cworth.org
Wed Aug 8 09:57:14 PDT 2007
On Wed, 8 Aug 2007 18:50:16 +0200, Tamas K Papp wrote:
>
> How could I get rid of both?
Snapping to device-space integers is what I would recommend.
Something like:
void
snap_point (cairo_t *cr, double *x, double *y)
{
cairo_user_to_device (cr, x, y);
*x = round (*x);
*y = round (*y);
cairo_device_to_user (cr, x, y);
}
snap_point (cr, &x1, &y1);
snap_point (cr, &x2, &y2);
cairo_rectangle (cr, x1, y2, x2 - x1, y2 - y2);
> Snapping to integer grids is something I
> want to avoid: I am drawing on vector and bitmap surfaces, and I would
> have to keep tack of which is which. But if there is not other
> solution, I can try to manage that, I just need to know.
Even if you didn't distinguish between vector and bitmap surfaces,
(which I can understand your reluctance to do), the device-space grid
for a vector surface such as PostScript or PDF will be 1 device-space
unit == 1 point (1/72 inch). Would a maximum error of half of 1/144
inch be a noticeable problem?
-Carl
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