note 78816 added to function.imagefilledpolygon
| From: | Arnapou at osu1 dot php dot net | Date: | Mon, 29 Oct 2007 14:49:00 +0000 |
| Subject: | note 78816 added to function.imagefilledpolygon | ||
| Groups: | php.notes | ||
| Request: | Send a blank email to php-notes+get-131812@lists.php.net to get a copy of this message | ||
I discovered that the GD imagefilledpolygon function is incorrect for some drawing with transparent
color (for example red 50% : RGBA = 255, 0, 0, 64).
I tried to draw a complex form with lots of points really near (1 pixel of distance) and a
transparent red.
The problem was : some border pixels were not drawn by the imagefilledpolygon but were drawn with
imagepolygon !?!?
So I wrote my own imagefilledpolygon function which work very well in all case I tested.
<?php
// $points should be an array of coordinates like that :
$points = array(
array(0, 0),
array(100, 50),
array(90, 100),
array(50, 50),
array(70, 30),
array(10, 10),
);
?>
<?php
function myimagefilledpolygon(& $img, $points, $color) {
$scanline = 99999;
// compute edges
$all_edges = array();
$n = count($points);
for($i=0; $i<$n; $i++) {
$p1 = $points[$i];
if ($i == $n-1) { $p2 = $points[0]; } else { $p2 = $points[$i+1]; }
$x1 = $p1[0]; $y1 = $p1[1];
$x2 = $p2[0]; $y2 = $p2[1];
if ($y1 != $y2) {
$invslope = ($x2 - $x1)/($y2 - $y1);
if ($y1 < $y2 ) {
$ymin = $y1;
$xval = $x1;
$ymax = $y2;
} else {
$ymin = $y2;
$xval = $x2;
$ymax = $y1;
}
$all_edges[] = array($ymin, $ymax, $xval, $invslope);
if ($ymin < $scanline) { $scanline = $ymin; }
} else {
if ($y1 < $scanline) { $scanline = $y1; }
if ($y2 < $scanline) { $scanline = $y2; }
}
}
// draw
$active = array();
do {
// add edges to active array
$tmp = array();
$n = count($all_edges);
for($i=0; $i<$n; $i++) {
if ($all_edges[$i][0] == $scanline) {
$active[] = $all_edges[$i];
} else {
$tmp[] = $all_edges[$i];
}
}
$all_edges = $tmp;
// remove previous edges from active array
$tmp = array();
$n = count($active);
for($i=0; $i<$n; $i++) {
if ($active[$i][1] > $scanline) {
$tmp[] = $active[$i];
}
}
$active = $tmp;
// sort active tab
$n = count($active);
for($i=0; $i<$n-1; $i++) {
$min = $i;
for($k=$i+1; $k<$n; $k++) {
if ($active[$k][2] < $active[$min][2]) { $min = $k; }
}
if ($i != $min) {
$tmp = $active[$i];
$active[$i] = $active[$min];
$active[$min] = $tmp;
}
}
// draw
$n = count($active);
for($i=0; $i<$n; $i+=2) {
if ($i+1 < $n) {
if ($tmp[$i][2] == $active[$i+1][2]) {
imagesetpixel($img, round($active[$i][2]), $scanline, $color);
} else {
imageline($img, round($active[$i][2]), $scanline, round($active[$i+1][2]), $scanline, $color);
}
}
}
// increment x values
$n = count($active);
for($i=0; $i<$n; $i++) { $active[$i][2] += $active[$i][3]; }
$scanline++;
} while (count($all_edges) + count($active) > 0);
}
?>
----
Server IP: 195.221.21.36
Probable Submitter: 171.16.2.5
----
Manual Page -- http://www.php.net/manual/en/function.imagefilledpolygon.php
Edit -- https://master.php.net/note/edit/78816
Del: integrated -- https://master.php.net/note/delete/78816/integrated
Del: useless -- https://master.php.net/note/delete/78816/useless
Del: bad code -- https://master.php.net/note/delete/78816/bad+code
Del: spam -- https://master.php.net/note/delete/78816/spam
Del: non-english -- https://master.php.net/note/delete/78816/non-english
Del: in docs -- https://master.php.net/note/delete/78816/in+docs
Del: other reasons-- https://master.php.net/note/delete/78816
Reject -- https://master.php.net/note/reject/78816
Search -- https://master.php.net/manage/user-notes.php