imagealphablending
Having tried long and hard to get a decent antialiased circle function, I finally gave in a wrote something from scratch. Its very very naive - basically examining every single pixel in the enclosing square, but as a result produces very nice antialiasing, with decent control over stroke width, antialiasing amount and tightness of antialiasing. I'm sure it could be optimised considerably, but it was fast enough for what I was doing. Hope its of some use.
<?php
function imagecircleaa($img, $cx, $cy, $r, $w, $s, $t, $color) // image, centerX, centerY, radius, stroke width, aa width, tightness, color
{
$adj = $w + $s;
$sCol = imagecolorallocate($img, $color['r'], $color['g'], $color['b']);
for($x = -$r - $adj; $x <= $r + $adj; $x++)
{
for($y = -$r - $adj; $y <= $r + $adj; $y++)
{
$d = sqrt($x * $x + $y * $y); // distance from pixel to center
$err = abs($d - $r); // absolute distance from pixel to circle edge
if($err <= $w / 2 + $s) // within the stroke width + smoothing radius
{
if($err <= $w / 2) // inside the stroke width so make it solid color
{
$aaCol = $sCol;
}
else // in the antialisaing region so make it a blended color
{
$err -= $w / 2; // adjust to the aliased part
$err = 1 - $err / $s; // adjust to between 0 and 1
$err = ($err - 0.5) * $t * 2; // adjust to -$t to +$t for tightness
$err = ($err / sqrt(1 + $err * $err) + 1) / 2; // sigmoid curve to smooth edges
$rgb = imagecolorat($img, $x + $cx, $y + $cy); // Get current background color
$rB = ($rgb >> 16) & 0xFF;
$gB = ($rgb >> 8) & 0xFF;
$bB = $rgb & 0xFF;
$rDelta = ($rB - $color['r']); // change in Red from background
$rComp = $rB - $rDelta * $err; // mix Red
$gDelta = ($gB - $color['g']); // change in Red from background
$gComp = $gB - $gDelta * $err; // mix Red
$bDelta = ($bB - $color['b']); // change in Red from background
$bComp = $bB - $bDelta * $err; // mix Red
$aaCol = imagecolorallocate($img, $rComp, $gComp, $bComp);
}
imagesetpixel($img, $x + $cx, $y + $cy, $aaCol);
}
}
}
}
$img = imagecreatetruecolor(500,500);
$cBlack = imagecolorallocate($img, 0, 0, 0);
$cGrey = imagecolorallocate($img, 120, 120, 120);
$cWhite = imagecolorallocate($img, 255, 255, 255);
imagefill($img, 0, 0, $cWhite);
imagepolygon($img, array(0, 0,200, 0, 200, 200, 0, 200), 4, cBlack);
$aWhite = array('r'=>255, 'g'=>255, 'b'=>255);
$aBlack = array('r'=>0, 'g'=>0, 'b'=>0);
$aRed = array('r'=>200, 'g'=>0, 'b'=>0);
$aGreen = array('r'=>0, 'g'=>200, 'b'=>0);
$aBlue = array('r'=>0, 'g'=>0, 'b'=>255);
// standard ellipse function for comparison
imageellipse($img, 100, 100, 50, 50, $cBlack);
// compare different tightnesses - good values are between 2 and 8
// note overall width is stroke width + 2 * aa width (e.g. 12 pixels below)
imagecircleaa($img, 50, 50, 25, 2, 5, 2, $aBlue);
imagecircleaa($img, 50, 150, 25, 2, 5, 8, $aBlue);
// different coloured background to show blending
imagefilledrectangle($img, 150,150, 200, 200, $cGrey);
imagecircleaa($img, 150, 150, 25, 3, 2, 2, $aRed);
// overlapping circles still aa nicely, although the colour blending algorithm produces quite dark intermediate shades
imagecircleaa($img, 150, 60, 25, 2, 3, 2, $aBlue);
imagecircleaa($img, 150, 50, 25, 2, 3, 2, $aGreen);
header("Content-type: image/png");
imagepng($img);
imagedestroy($img);
?>
imageantialias
(PHP 4 >= 4.3.2, PHP 5)
imageantialias — アンチエイリアス機能を使用すべきかどうかを判断する
説明
bool imageantialias
( resource $image
, bool $enabled
)
直線や多角形を高速に描画するためのアンチエイリアス機能を有効にします。 アルファコンポーネントはサポートしていません。ダイレクトブレンド操作を 使用します。truecolor 画像に対してのみ動作します。
thickness および styled はサポートしていません。
背景色が透明な場合にアンチエイリアス機能を使用すると、予期せぬ結果に 終わることがあります。ブレンドメソッドでは、背景色が使用されます。 アルファコンポーネントをサポートしていないため、アルファコンポーネントに 基づいたアンチエイリアス手法は使用できません。
返り値
成功した場合に TRUE を、失敗した場合に FALSE を返します。
例
例1 2 本の直線のうち一方にアンチエイリアスを有効にする
<?php
// アンチエイリアス画像と通常の画像を用意します
$aa = imagecreatetruecolor(400, 100);
$normal = imagecreatetruecolor(200, 100);
// アンチエイリアスを有効にします
imageantialias($aa, true);
// 色を割り当てます
$red = imagecolorallocate($normal, 255, 0, 0);
$red_aa = imagecolorallocate($aa, 255, 0, 0);
// 一方はアンチエイリアスを有効にした状態で 2 本の直線を描画します
imageline($normal, 0, 0, 200, 100, $red);
imageline($aa, 0, 0, 200, 100, $red_aa);
// ふたつの画像を横に並べて出力します (アンチエイリアス: 左、通常: 右)
imagecopymerge($aa, $normal, 200, 0, 0, 0, 200, 100, 100);
// 画像を出力します
header('Content-type: image/png');
imagepng($aa);
imagedestroy($aa);
imagedestroy($normal);
?>
上の例の出力は、 たとえば以下のようになります。
注意
注意: この関数は、PHP がバンドル版の GD ライブラリで コンパイルされている場合のみ使用可能です。
add a note
User Contributed Notesimageantialias
dsl101
31-Jul-2009 03:48
31-Jul-2009 03:48
Ulrich M.
20-Dec-2007 04:07
20-Dec-2007 04:07
An updated version of my antialiased arc script is now available at:
http://mierendo.com/software/antialiased_arcs/
Have fun with it!
Godfather of Image Processing
22-Feb-2007 06:05
22-Feb-2007 06:05
Of course, this IS a way to do antialiasing. Graphiccards do so. But for good results you should use at least a 4 times bigger source image than the destination to scale down. This is a 16 times higher fillrate. If you only use the proposed doublesized image, quality is still poor...
padigan
06-Feb-2007 11:13
06-Feb-2007 11:13
If you can't be bothered creating (or searching for) a full screen antialias function.
You can actually cheat (well a bit of a dirty inefficient hack really!!)
and perform a fake antialias on an image by using 'imagecopyresampled'...
first create your source image twice the size of what you really want.
Then use 'imagecopyresampled' to shrink it to half the size, the function
automatically interpolates pixels to create an antialias effect!
I've used this in a pie chart function and it works brilliantly,
not as slow as I thought it might be!
the rough code below should give you the idea...
<?php
$realWidth = 500;
$realHeight = 500;
$srcWidth = $realWidth * 2;
$srcHeight = $realHeight * 2;
// create the larger source image
$srcImage = imagecreatetruecolor($srcWidth,$srcHeight);
// create the real/final image
$destImage = imagecreatetruecolor($realWidth,$realHeight);
// now do whatever you want to draw in the source image
// blah....
// now the picture is finished, do the shrink...
imagecopyresampled($destImage,$srcImage,0,0,0,0,
$realWidth,$realHeight,$srcWidth,$srcHeight);
// now just do whatever you want with '$destImage' (e.g. display or output to file!)
?>
Ulrich Mierendorff
10-Aug-2006 07:39
10-Aug-2006 07:39
I've written a php function which draws antialiased and filled elliptic arcs (segments of ellipses or full ellipses). It does not require the imageantialias function of php!
It's available at
http://icewind.ic.funpic.de/index.php?content=ellipse
Best Regards,
Ulrich
php at 3d-box dot com
08-Jul-2006 04:55
08-Jul-2006 04:55
This might help some people but I have created an antialiased, filled, ellipse function - the source for which is here:-
http://personal.3d-box.com/php/filledellipseaa.php
As the code is too much to put here!
jb at flamedesign dot dk
30-Mar-2006 10:37
30-Mar-2006 10:37
Official GD Lib manual link:
http://www.boutell.com/gd/manual2.0.33.html#gdImageSetAntiAliased
n-dream at gmx dot ch
18-Feb-2006 06:18
18-Feb-2006 06:18
The following function draws an AntiAliased (unfilled) Ellipse.
It is used just liked the nomral ImageEllipse function.
The optional parameter sets the number of segments...
function ImageEllipseAA( &$img, $x, $y, $w, $h,$color,$segments=70)
{
$w=$w/2;
$h=$h/2;
$jump=2*M_PI/$segments;
$oldx=$x+sin(-$jump)*$w;
$oldy=$y+cos(-$jump)*$h;
for($i=0;$i<2*(M_PI);$i+=$jump)
{
$newx=$x+sin($i)*$w;
$newy=$y+cos($i)*$h;
ImageLine($img,$newx,$newy,$oldx,$oldy,$color);
$oldx=$newx;
$oldy=$newy;
}
}
klaas at kosmokrator dot com
15-Feb-2006 01:22
15-Feb-2006 01:22
Here is an optimized version of the optimized version of the antialiased circle function by sebbi: (more than 20 times faster)...
<?php
function imageSmoothCircle( &$img, $cx, $cy, $cr, $color ) {
$ir = $cr;
$ix = 0;
$iy = $ir;
$ig = 2 * $ir - 3;
$idgr = -6;
$idgd = 4 * $ir - 10;
$fill = imageColorExactAlpha( $img, $color[ 'R' ], $color[ 'G' ], $color[ 'B' ], 0 );
imageLine( $img, $cx + $cr - 1, $cy, $cx, $cy, $fill );
imageLine( $img, $cx - $cr + 1, $cy, $cx - 1, $cy, $fill );
imageLine( $img, $cx, $cy + $cr - 1, $cx, $cy + 1, $fill );
imageLine( $img, $cx, $cy - $cr + 1, $cx, $cy - 1, $fill );
$draw = imageColorExactAlpha( $img, $color[ 'R' ], $color[ 'G' ], $color[ 'B' ], 42 );
imageSetPixel( $img, $cx + $cr, $cy, $draw );
imageSetPixel( $img, $cx - $cr, $cy, $draw );
imageSetPixel( $img, $cx, $cy + $cr, $draw );
imageSetPixel( $img, $cx, $cy - $cr, $draw );
while ( $ix <= $iy - 2 ) {
if ( $ig < 0 ) {
$ig += $idgd;
$idgd -= 8;
$iy--;
} else {
$ig += $idgr;
$idgd -= 4;
}
$idgr -= 4;
$ix++;
imageLine( $img, $cx + $ix, $cy + $iy - 1, $cx + $ix, $cy + $ix, $fill );
imageLine( $img, $cx + $ix, $cy - $iy + 1, $cx + $ix, $cy - $ix, $fill );
imageLine( $img, $cx - $ix, $cy + $iy - 1, $cx - $ix, $cy + $ix, $fill );
imageLine( $img, $cx - $ix, $cy - $iy + 1, $cx - $ix, $cy - $ix, $fill );
imageLine( $img, $cx + $iy - 1, $cy + $ix, $cx + $ix, $cy + $ix, $fill );
imageLine( $img, $cx + $iy - 1, $cy - $ix, $cx + $ix, $cy - $ix, $fill );
imageLine( $img, $cx - $iy + 1, $cy + $ix, $cx - $ix, $cy + $ix, $fill );
imageLine( $img, $cx - $iy + 1, $cy - $ix, $cx - $ix, $cy - $ix, $fill );
$filled = 0;
for ( $xx = $ix - 0.45; $xx < $ix + 0.5; $xx += 0.2 ) {
for ( $yy = $iy - 0.45; $yy < $iy + 0.5; $yy += 0.2 ) {
if ( sqrt( pow( $xx, 2 ) + pow( $yy, 2 ) ) < $cr ) $filled += 4;
}
}
$draw = imageColorExactAlpha( $img, $color[ 'R' ], $color[ 'G' ], $color[ 'B' ], ( 100 - $filled ) );
imageSetPixel( $img, $cx + $ix, $cy + $iy, $draw );
imageSetPixel( $img, $cx + $ix, $cy - $iy, $draw );
imageSetPixel( $img, $cx - $ix, $cy + $iy, $draw );
imageSetPixel( $img, $cx - $ix, $cy - $iy, $draw );
imageSetPixel( $img, $cx + $iy, $cy + $ix, $draw );
imageSetPixel( $img, $cx + $iy, $cy - $ix, $draw );
imageSetPixel( $img, $cx - $iy, $cy + $ix, $draw );
imageSetPixel( $img, $cx - $iy, $cy - $ix, $draw );
}
}
$img = imageCreateTrueColor( 320, 240 );
imageSmoothCircle( $img, 160, 120, 100, array( 'R' => 0xCC, 'G' => 0x33, 'B' => 0x00 ) );
imageSmoothCircle( $img, 170, 110, 75, array( 'R' => 0xDD, 'G' => 0x66, 'B' => 0x00 ) );
imageSmoothCircle( $img, 180, 100, 50, array( 'R' => 0xEE, 'G' => 0x99, 'B' => 0x00 ) );
imageSmoothCircle( $img, 190, 90, 25, array( 'R' => 0xFF, 'G' => 0xCC, 'B' => 0x00 ) );
header( 'Content-Type: image/png' );
imagePNG( $img );
?>
voinic at NOSgmailPAM dot com
12-Jan-2006 10:22
12-Jan-2006 10:22
The only trick I found to draw an antialiased polygon AND keep it transparent (to use them as overlays in google maps for example)... make two images and merge them. Order of operations is important and the transparency color of the final image must be set after the merge:
<?
header("Content-type: image/png");
$values = array(
40, 50, // Point 1 (x, y)
20, 240, // Point 2 (x, y)
60, 60, // Point 3 (x, y)
240, 20, // Point 4 (x, y)
50, 40, // Point 5 (x, y)
10, 10 // Point 6 (x, y)
);
$im = imagecreate(250, 250);
$bg = imagecolorallocate($im, 255, 255, 255);
$im2 = imagecreatetruecolor(250, 250);
$bg2 = imagecolorallocate($im2, 255, 255, 255);
imagefilledrectangle($im2,0,0,249,249,$bg2);
imagecolortransparent($im2, $bg);
imageantialias($im2, true);
$c_red = imagecolorallocate($im2, 255, 0, 0);
imagepolygon($im2, $values, 6, $c_red);
imageantialias($im2, false);
imagecopymerge($im, $im2,0,0,0,0,250,250,50);
imagecolortransparent($im, $bg);
$c_red_alpha = imagecolorallocatealpha($im, 255, 0, 0, 60);
imagefilledpolygon($im, $values, 6, $c_red_alpha);
imagepng($im);
imagedestroy($im);
imagedestroy($im2);
?>
sebbi at conceptT dot com
26-Sep-2005 02:06
26-Sep-2005 02:06
I did a search in google and got following url:
http://www.isocalc.com/tutorials/antialias.htm
With this tutorial I was able to write a function to convert this algorithm into php, the result for a filled circel is this:
<?php
function imagefilledcircleantialiased(&$im, $cx, $cy, $r, $fgcolor, $bgcolor) {
$fgcolors = imagecolorsforindex($im,$fgcolor);
$bgcolors = imagecolorsforindex($im,$bgcolor);
for ( $x = $cx - $r; $x <= $cx + $r; $x++ ) {
for ( $y = $cy - $r; $y <= $cy + $r; $y++ ) {
$rx = $x - $cx; $ry = $y - $cy;
$ir = sqrt(( $rx == 0 ? 0 : pow($rx - 0.5*abs($rx)/$rx, 2) ) + ( $ry == 0 ? 0 : pow($ry - 0.5*abs($ry)/$ry, 2) ));
$or = sqrt(( $rx == 0 ? 0 : pow($rx + 0.5*abs($rx)/$rx, 2) ) + ( $ry == 0 ? 0 : pow($ry + 0.5*abs($ry)/$ry, 2) ));
if ( $or <= $r ) {
imagesetpixel($im, $x, $y, $fgcolor);
}
elseif ( $ir < $r ) {
$filled = 0;
for ( $xx = $x - 0.45; $xx < $x + 0.5; $xx+=0.1 ) {
for ( $yy = $y - 0.45; $yy < $y + 0.5; $yy+=0.1 ) {
$rxx = $xx - $cx; $ryy = $yy - $cy;
if ( sqrt(pow($rxx, 2) + pow($ryy, 2)) < $r ) $filled++;
}
}
$red = round($bgcolors['red'] + ( $fgcolors['red'] - $bgcolors['red'] ) * $filled / 100);
$green = round($bgcolors['green'] + ( $fgcolors['green'] - $bgcolors['green'] ) * $filled / 100);
$blue = round($bgcolors['blue'] + ( $fgcolors['blue'] - $bgcolors['blue'] ) * $filled / 100);
imagesetpixel($im, $x, $y, imagecolorclosest($im, $red, $green, $blue));
}
}
}
}
$width = 160;
$height = 200;
$r = 20;
$bgc = "651713";
$fgc = "b12b2c";
$im = imagecreate($width, $height);
$bgcolor = imagecolorallocate($im, hexdec(substr($bgc, 0, 2)), hexdec(substr($bgc, 2, 2)), hexdec(substr($bgc, 4, 2)));
for( $i = 0; $i < 100; $i++ ) {
imagecolorallocate($im, ( hexdec(substr($fgc, 0, 2)) + $i*hexdec(substr($bgc, 0, 2))) / ($i + 1), ( hexdec(substr($fgc, 2, 2)) + $i*hexdec(substr($bgc, 2, 2))) / ($i + 1), ( hexdec(substr($fgc, 4, 2)) + $i*hexdec(substr($bgc, 4, 2))) / ($i + 1));
}
$fgcolor = imagecolorclosest($im, hexdec(substr($fgc, 0, 2)), hexdec(substr($fgc, 2, 2)), hexdec(substr($fgc, 4, 2)));
imagefilledcircleantialiased($im, 80, 100, $r, $fgcolor, $bgcolor);
header("Content-Type: image/png");
imagepng($im);
?>
An improvement would be to draw the inner rectangle or more rectangles in the circle with the builtin rectangle function to reduce the usage of imagesetpixel() from (2*r)^2 to 2*Pi*(r + epsilon), in other words, the dependency on r would break down from square to linear.
Another improvement would be to determine filled and unfilled triangles in the observed pixel and calculate their areas, so we can get rid of the inner loops for getting the fraction filled/unfilled.
One can easily modify this function to solve other problems like lines, unfilled circles, etc.
trimbo
06-Sep-2005 07:25
06-Sep-2005 07:25
So far using PHP 5.0.4 I've managed to get Imageantialias() to work well with:
ImageLine()
ImagePolygon()
but not with:
ImageArc()
ImageEllipse()
ImageFilled*()
You can still draw antialiased filled polygons by drawing a hollow polygon on top of a filled one with the same dimensions:
<?php
$points=array($x,$y, $x2,$y2, $x3,$y3);
imageFilledPolygon($im, $points, 3, $gray );
imagePolygon($im, $points, 3, $gray );
?>
klaas at kosmokrator dot com
24-May-2004 02:21
24-May-2004 02:21
I have optimized the "imageSmoothLine" function by logang.
sample and download at:
http://www.kosmokrator.com/download/php/