Hi,I continued to work on the anti-aliasing, specifically the lack of aliasing when the line hits the edge of the image.
Attached is a patch that is applied AFTER the last one I posted. It cleans up the lines, so tiled images now look awesome.
Also attached is the build-script and the last diff, plus the little segfault test file, for completeness.
Please let me know what you are going to do with these patches. I intend to get them applied upstream, I'm hoping you could be the one to do it since you are the maintainer of its package and are therefore a good guy.
cheers, Paul
--- libgd2-2.0.33/gd.c 2006-04-21 11:31:18.000000000 +0800
+++ libgd2-2.0.33/gd.c 2006-04-21 11:31:15.000000000 +0800
@@ -3095,7 +3095,8 @@
/* TBB: set the last pixel for consistency (<=) */
while ((x >> 16) <= x2) {
gdImageSetAAPixelColor(im, x >> 16, y >> 16, col, (y >>
8) & 0xFF);
- gdImageSetAAPixelColor(im, x >> 16, (y >> 16) + 1,col,
(~y >> 8) & 0xFF);
+ if ((y >> 16) + 1 <= im->cy2)
+ gdImageSetAAPixelColor(im, x >> 16, (y >> 16) + 1,col, (~y >> 8) &
0xFF);
x += (1 << 16);
y += inc;
}
@@ -3116,7 +3117,8 @@
/* TBB: set the last pixel for consistency (<=) */
while ((y>>16) <= y2) {
gdImageSetAAPixelColor(im, x >> 16, y >> 16, col, (x >>
8) & 0xFF);
- gdImageSetAAPixelColor(im, (x >> 16) + 1, (y >>
16),col, (~x >> 8) & 0xFF);
+ if ((x >> 16) + 1 <= im->cx2)
+ gdImageSetAAPixelColor(im, (x >> 16) + 1, (y >> 16),col, (~x >> 8)
& 0xFF);
x += inc;
y += (1<<16);
}
--- libgd2-2.0.33/gd.c 2006-04-21 16:37:55.000000000 +0800
+++ libgd2-2.0.33/gd.c 2006-04-21 16:39:07.000000000 +0800
@@ -3055,6 +3055,9 @@
im->tpixels[y][x]=gdTrueColorAlpha(dr, dg, db, gdAlphaOpaque);
}
+/* simple helper */
+inline int min_int(int a, int b) { return (a < b ? a : b); }
+
static void gdImageAALine (gdImagePtr im, int x1, int y1, int x2, int y2, int
col)
{
/* keep them as 32bits */
@@ -3065,11 +3068,15 @@
gdImageLine(im, x1, y1, x2, y2, col);
return;
}
- /* TBB: use the clipping rectangle */
- if (clip_1d (&x1, &y1, &x2, &y2, im->cx1, im->cx2) == 0)
- return;
- if (clip_1d (&y1, &x1, &y2, &x2, im->cy1, im->cy2) == 0)
- return;
+
+ /* TBB: use the clipping rectangle */
+ /* use expanded image bounds to ensure we get all the AA pixels drawn on
the edges */
+ /* Note the +1 and -1 */
+ if (clip_1d (&x1, &y1, &x2, &y2, im->cx1-1, im->cx2+1) == 0)
+ return;
+ if (clip_1d (&y1, &x1, &y2, &x2, im->cy1-1, im->cy2+1) == 0)
+ return;
+
dx = x2 - x1;
dy = y2 - y1;
@@ -3089,15 +3096,25 @@
dx = x2 - x1;
dy = y2 - y1;
}
- x = x1 << 16;
+ x = x1;
y = y1 << 16;
inc = (dy * 65536) / dx;
+
/* TBB: set the last pixel for consistency (<=) */
- while ((x >> 16) <= x2) {
- gdImageSetAAPixelColor(im, x >> 16, y >> 16, col, (y >>
8) & 0xFF);
- if ((y >> 16) + 1 <= im->cy2)
- gdImageSetAAPixelColor(im, x >> 16, (y >> 16) + 1,col, (~y >> 8) &
0xFF);
- x += (1 << 16);
+ /* Constrain the loop to the image bounds */
+ if (x < 0)
+ {
+ y -= inc * x;
+ x = 0;
+ }
+ x2 = min_int(x2,im->cx2);
+ while (x <= x2) {
+ int py = y >> 16;
+ if (py >= im->cy1 && py <= im->cy2)
+ gdImageSetAAPixelColor(im, x, py, col, (y >> 8) & 0xFF);
+ if (py + 1 <= im->cy2)
+ gdImageSetAAPixelColor(im, x, py + 1,col, (~y >> 8) & 0xFF);
+ x += 1;
y += inc;
}
} else {
@@ -3112,15 +3129,26 @@
dy = y2 - y1;
}
x = x1 << 16;
- y = y1 << 16;
+ // y = y1 << 16;
+ y = y1;
inc = (dx * 65536) / dy;
+
/* TBB: set the last pixel for consistency (<=) */
- while ((y>>16) <= y2) {
- gdImageSetAAPixelColor(im, x >> 16, y >> 16, col, (x >>
8) & 0xFF);
- if ((x >> 16) + 1 <= im->cx2)
- gdImageSetAAPixelColor(im, (x >> 16) + 1, (y >> 16),col, (~x >> 8)
& 0xFF);
+ /* Constrain the loop to the image bounds */
+ if (y < 0)
+ {
+ x -= inc * y;
+ y = 0;
+ }
+ y2 = min_int(y2,im->cy2);
+ while (y <= y2) {
+ int px = x >> 16;
+ if (px >= im->cx1 && px <= im->cx2)
+ gdImageSetAAPixelColor(im, px, y, col, (x >> 8) & 0xFF);
+ if (px + 1 <= im->cx2)
+ gdImageSetAAPixelColor(im, px + 1, y,col, (~x >> 8) & 0xFF);
x += inc;
- y += (1<<16);
+ y += 1;
}
}
}
make_libgd2.sh
Description: Bourne shell script
#include <gd.h>
int main()
{
gdImagePtr im = gdImageCreateTrueColor(100,100);
int colour = gdTrueColorAlpha(100,100,100,100);
gdImageSetAntiAliased(im,colour);
gdImageLine(im, 95, 100, 100, 98, gdAntiAliased);
return 0;
}
