On Wed, Sep 30, 2009 at 07:56:32AM -0700, Randolph Bentson wrote:
> I've found that wide lines drawn with PIL 1.1.6 have a directional
> dependence, e.g., lines from (0,0) to (-100,0) are thinner than those
> from (0,0) to (0,-100).
A few days ago I posted a hack which reduced the magnitude of the problem.
The following patch does a better job at little additional cost.
I've introduced variables dX and dY to improve the readability of the
code which computes the values of the pixel-based dx and dy values. The
reference to "diagonal lines" doesn't implement proper antialiasing,
but it improves things with modest code change.)
Feedback is welcome because I do hope this'll get in the 1.1.7 release.
--- OLD_Draw.c 2009-10-03 14:44:31.000000000 -0700
+++ Draw.c 2009-10-03 15:42:41.000000000 -0700
@@ -665,6 +665,7 @@
Edge e[4];
+ int dX, dY;
int dx, dy;
double d;
@@ -675,18 +676,34 @@
return 0;
}
- dx = x1-x0;
- dy = y1-y0;
+ dX = x1-x0;
+ dY = y1-y0;
- if (dx == 0 && dy == 0) {
+ if (dX == 0 && dY == 0) {
draw->point(im, x0, y0, ink);
return 0;
}
- d = width / sqrt(dx*dx + dy*dy) / 2.0;
+ d = width / sqrt(dX*dX + dY*dY) / 2.0;
- dx = (int) (d * (y1-y0) + 0.5);
- dy = (int) (d * (x1-x0) + 0.5);
+ /* Negative values are rounded down and positive
+ values are rounded up, else the deltas disappear!
+ */
+ if (dY < 0) dx = (int) (d * dY - 0.5);
+ else dx = (int) (d * dY + 0.5);
+ if (dX < 0) dy = (int) (d * dX - 0.5);
+ else dy = (int) (d * dX + 0.5);
+
+ /* This is necessary because diagonal lines are too wide.
+ */
+ if ( 4*(dx*dx+dy*dy) > (width*width) ){
+ if (abs(dx) > abs(dy))
+ if (dx < 0) dx ++;
+ else dx --;
+ else
+ if (dy < 0) dy ++;
+ else dy --;
+ }
add_edge(e+0, x0 - dx, y0 + dy, x1 - dx, y1 + dy);
add_edge(e+1, x1 - dx, y1 + dy, x1 + dx, y1 - dy);
--
Randolph Bentson
bent...@holmsjoen.com
_______________________________________________
Image-SIG maillist - Image-SIG@python.org
http://mail.python.org/mailman/listinfo/image-sig
