function imageSmoothArc(&$img, $cx, $cy, $w, $h, $color, $start, $stop)
{
// Originally written from scratch by Ulrich Mierendorff, 06/2006
// Rewritten and improved, 04/2007, 07/2007
// compared to old version:
// + Support for transparency added
// + Improved quality of edges & antialiasing
// note: This function does not represent the fastest way to draw elliptical
// arcs. It was written without reading any papers on that subject. Better
// algorithms may be twice as fast or even more.
// what it cannot do: It does not support outlined arcs, only filled
// Parameters:
// $cx - Center of ellipse, X-coord
// $cy - Center of ellipse, Y-coord
// $w - Width of ellipse ($w >= 2)
// $h - Height of ellipse ($h >= 2 )
// $color - Color of ellipse as a four component array with RGBA
// $start - Starting angle of the arc, no limited range!
// $stop - Stop angle of the arc, no limited range!
// $start _can_ be greater than $stop!
// If any value is not in the given range, results are undefined!
// This script does not use any special algorithms, everything is completely
// written from scratch; see http://de.wikipedia.org/wiki/Ellipse for formulas.
while ($start < 0) {
$start += 2 * M_PI;
}
while ($stop < 0) {
$stop += 2 * M_PI;
}
while ($start > 2 * M_PI) {
$start -= 2 * M_PI;
}
while ($stop > 2 * M_PI) {
$stop -= 2 * M_PI;
}
if ($start > $stop) {
imageSmoothArc($img, $cx, $cy, $w, $h, $color, $start, 2 * M_PI);
imageSmoothArc($img, $cx, $cy, $w, $h, $color, 0, $stop);
return;
}
$a = 1.0 * round($w / 2);
$b = 1.0 * round($h / 2);
$cx = 1.0 * round($cx);
$cy = 1.0 * round($cy);
$aaAngle = atan($b * $b / ($a * $a) * tan(0.25 * M_PI));
$aaAngleX = $a * cos($aaAngle);
$aaAngleY = $b * sin($aaAngle);
$a -= 0.5;
// looks better...
$b -= 0.5;
for ($i = 0; $i < 4; $i++) {
if ($start < ($i + 1) * M_PI / 2) {
if ($start > $i * M_PI / 2) {
if ($stop > ($i + 1) * M_PI / 2) {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $aaAngleX, $aaAngleY, $color, $start, ($i + 1) * M_PI / 2, $i);
} else {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $aaAngleX, $aaAngleY, $color, $start, $stop, $i);
break;
}
} else {
if ($stop > ($i + 1) * M_PI / 2) {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $aaAngleX, $aaAngleY, $color, $i * M_PI / 2, ($i + 1) * M_PI / 2, $i);
} else {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $aaAngleX, $aaAngleY, $color, $i * M_PI / 2, $stop, $i);
break;
}
}
}
}
}
function imageSmoothArc(&$img, $cx, $cy, $w, $h, $color, $start, $stop)
{
while ($start < 0) {
$start += 2 * M_PI;
}
while ($stop < 0) {
$stop += 2 * M_PI;
}
while ($start > 2 * M_PI) {
$start -= 2 * M_PI;
}
while ($stop > 2 * M_PI) {
$stop -= 2 * M_PI;
}
if ($start > $stop) {
imageSmoothArc(&$img, $cx, $cy, $w, $h, $color, $start, 2 * M_PI);
imageSmoothArc(&$img, $cx, $cy, $w, $h, $color, 0, $stop);
return;
}
$a = 1.0 * round($w / 2);
$b = 1.0 * round($h / 2);
$cx = 1.0 * round($cx);
$cy = 1.0 * round($cy);
for ($i = 0; $i < 4; $i++) {
if ($start < ($i + 1) * M_PI / 2) {
if ($start > $i * M_PI / 2) {
if ($stop > ($i + 1) * M_PI / 2) {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $color, $start, ($i + 1) * M_PI / 2, $i);
} else {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $color, $start, $stop, $i);
break;
}
} else {
if ($stop > ($i + 1) * M_PI / 2) {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $color, $i * M_PI / 2, ($i + 1) * M_PI / 2, $i);
} else {
imageSmoothArcDrawSegment($img, $cx, $cy, $a, $b, $color, $i * M_PI / 2, $stop, $i);
break;
}
}
}
}
}
