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imageantialias (PHP 4 >= 4.3.2, PHP 5) imageantialias -- Should antialias functions be used or not Описаниеbool imageantialias ( resource image, bool on )
Activate the fast drawing antialiased methods for lines and wired polygons.
It does not support alpha components. It works using a direct blend
operation. It works only with truecolor images.
Thickness and styled are not supported.
Using antialiased primitives with transparent background color can end with
some unexpected results. The blend method uses the background color as any
other colors. The lack of alpha component support does not allow an alpha
based antialiasing method.
Список параметров
imageAn image resource, returned by one of the image creation functions,
such as imagecreatetruecolor(). on
Wether to enable antialiasing or not.
Возвращаемые значения
Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.
ПримечанияЗамечание: Эта функция доступна только в том
случае, если PHP был скомпилирован со встроенной библиотекой GD.
Godfather of Image Processing
22-Feb-2007 10:05
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 03:13
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;
$srcImage = imagecreatetruecolor($srcWidth,$srcHeight);
$destImage = imagecreatetruecolor($realWidth,$realHeight);
imagecopyresampled($destImage,$srcImage,0,0,0,0,
$realWidth,$realHeight,$srcWidth,$srcHeight);
?>
n-dream at gmx dot ch
18-Feb-2006 10:18
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 05:22
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 02:22
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 07:06
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 12:25
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 );
?>
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