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PHP : Function Reference : Image Functions : imageline

imageline

Draw a line (PHP 4, PHP 5)
bool imageline ( resource image, int x1, int y1, int x2, int y2, int color )

Example 1016. Drawing a thick line

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<?php

function imagelinethick($image, $x1, $y1, $x2, $y2, $color, $thick = 1)
{
   /* this way it works well only for orthogonal lines
   imagesetthickness($image, $thick);
   return imageline($image, $x1, $y1, $x2, $y2, $color);
   */
   if ($thick == 1) {
       return imageline($image, $x1, $y1, $x2, $y2, $color);
   }
   $t = $thick / 2 - 0.5;
   if ($x1 == $x2 || $y1 == $y2) {
       return imagefilledrectangle($image, round(min($x1, $x2) - $t), round(min($y1, $y2) - $t), round(max($x1, $x2) + $t), round(max($y1, $y2) + $t), $color);
   }
   $k = ($y2 - $y1) / ($x2 - $x1); //y = kx + q
   $a = $t / sqrt(1 + pow($k, 2));
   $points = array(
       round($x1 - (1+$k)*$a), round($y1 + (1-$k)*$a),
       round($x1 - (1-$k)*$a), round($y1 - (1+$k)*$a),
       round($x2 + (1+$k)*$a), round($y2 - (1-$k)*$a),
       round($x2 + (1-$k)*$a), round($y2 + (1+$k)*$a),
   );
   imagefilledpolygon($image, $points, 4, $color);
   return imagepolygon($image, $points, 4, $color);
}

?>

Related Examples ( Source code ) » imageline

Examples ( Source code ) » Color
Examples ( Source code ) » Drawing Lines
Examples ( Source code ) » Using imagefill()
Examples ( Source code ) » Drawing a Line with imageline()
Examples ( Source code ) » Round rectangle Demo

Code Examples / Notes » imageline

pb_2001
This is a function to make a dotted line. It accepts (it actually requires) 7 parameters and returns 1 if everything went OK and 0 if there was a problem.
int imagelinedotted ( resource im, int x1, int y1, int x2, int y2, int dist, int col )
imagelinedotted() draws a line from x1, y1 to x2, y2 (top left is 0, 0) in image im of colour col where dist defines the distance (measured in pixels) between one dot and another.
<?php
function imagelinedotted ($im, $x1, $y1, $x2, $y2, $dist, $col) {
$transp = imagecolortransparent ($im);

$style = array ($col);

for ($i=0; $i<$dist; $i++) {
array_push($style, $transp); // Generate style array - loop needed for customisable distance between the dots
}

imagesetstyle ($im, $style);
return (integer) imageline ($im, $x1, $y1, $x2, $y2, IMG_COLOR_STYLED);
imagesetstyle ($im, array($col)); // Reset style - just in case...
}
?>

likavcan
This function draws arrow.
function arrow($im, $x1, $y1, $x2, $y2, $alength, $awidth, $color) {
$distance = sqrt(pow($x1 - $x2, 2) + pow($y1 - $y2, 2));
$dx = $x2 + ($x1 - $x2) * $alength / $distance;
$dy = $y2 + ($y1 - $y2) * $alength / $distance;
$k = $awidth / $alength;
$x2o = $x2 - $dx;
$y2o = $dy - $y2;
$x3 = $y2o * $k + $dx;
$y3 = $x2o * $k + $dy;
$x4 = $dx - $y2o * $k;
$y4 = $dy - $x2o * $k;
imageline($im, $x1, $y1, $dx, $dy, $color);
imageline($im, $x3, $y3, $x4, $y4, $color);
imageline($im, $x3, $y3, $x2, $y2, $color);
imageline($im, $x2, $y2, $x4, $y4, $color);
}

eviloverlord
This code is used to draw a board of hexagons (for games, classes, etc.)
<?php
//Draws a hexagonal board
// User-defined values
$maxTiles = 7; //The number of tiles at the center (widest part) of the board
$minTiles = 4; //The number of tiles at the edges of the board
$side = 30; //The length of the sides of the tiles in pixels
$bgColor = array(0, 0, 0); //The background color in RGB format
$fgColor = array(255, 255, 255);//The foreground color in RGB format
//Calculated values
$widthInTiles = range($maxTiles, $minTiles); //In our example: 7, 6, 5, 4
$rowsInTiles = count($widthInTiles)*2-1; //the total number of rows on our board
$xSide = $side*sin(deg2rad(60)); //the length of the x-part of the angled sides
$ySide = $side*sin(deg2rad(30)); //the length of the y-part of the angled sides
$boardWidth = $xSide*$widthInTiles[0]*2; //The entire width of the board
$boardHeight = $rowsInTiles*($side + $ySide) + $ySide; //The entire height of the board
// create a blank image and allocate the foreground, background colors
$image = imagecreate($boardWidth, $boardHeight);
$bg = imagecolorallocate($image, $bgColor[0], $bgColor[1], $bgColor[2]);
$fg = imagecolorallocate($image, $fgColor[0], $fgColor[1], $fgColor[2]);
// draw the board
$row = 0;
foreach($widthInTiles as $tiles)
{
for ($i = 0; $i < $tiles+1; $i++)
{
$x1 = $row*$xSide + $i*$xSide*2;
$y1 = $boardHeight/2;
$y1Dif = ($side/2) + $row*($side+$ySide);
$x2 = $x1 + $xSide;
$y2 = $y1;
$y2Dif = $ySide;
$x3 = $x2 + $xSide;
if ($i < $tiles)
{
imageline($image, $x1, $y1 - $y1Dif, $x2, $y2 - $y1Dif - $y2Dif, $fg);
imageline($image,  $x1, $y1 + $y1Dif, $x2, $y2 + $y1Dif + $y2Dif, $fg);
imageline($image, $x2, $y2 - $y1Dif - $y2Dif, $x3, $y1 - $y1Dif, $fg);
imageline($image, $x2, $y2 + $y1Dif + $y2Dif, $x3, $y1 + $y1Dif, $fg);
}

imageline($image, $x1, $y1 - $y1Dif, $x1, $y1 - $y1Dif + $side, $fg);
imageline($image, $x1, $y1 + $y1Dif, $x1, $y1 + $y1Dif - $side, $fg);
}
$row++;
}
// output the picture
header("Content-type: image/png");
imagepng($image);
imagedestroy($image);
?>

meid
Some simple code to draw lines with specific thickness using "imagefilledpolygon". Useful if your gdlib does not support "imagesetthickness".
<?
function dickelinie($img,$start_x,$start_y,$end_x,$end_y,$color,$thickness)
{
$angle=(atan2(($start_y - $end_y),($end_x - $start_x)));
$dist_x=$thickness*(sin($angle));
$dist_y=$thickness*(cos($angle));

$p1x=ceil(($start_x + $dist_x));
$p1y=ceil(($start_y + $dist_y));
$p2x=ceil(($end_x + $dist_x));
$p2y=ceil(($end_y + $dist_y));
$p3x=ceil(($end_x - $dist_x));
$p3y=ceil(($end_y - $dist_y));
$p4x=ceil(($start_x - $dist_x));
$p4y=ceil(($start_y - $dist_y));

$array=array(0=>$p1x,$p1y,$p2x,$p2y,$p3x,$p3y,$p4x,$p4y);
imagefilledpolygon ( $img, $array, (count($array)/2), $color );
}
// Example:
header ("Content-type: image/jpeg");
$img = ImageCreate (210, 210) or die("Cannot Initialize new GD image stream ");
$backgroundcolor = ImageColorAllocate ($img, 255, 255, 255);
$orange = ImageColorAllocate($img, 252, 102, 4);
dickelinie($img, 10, 10, 10, 200,$orange,2);
dickelinie($img, 10, 200, 200, 10,$orange,2);
dickelinie($img, 200, 10, 200, 200,$orange,2);
imagejpeg($img);  
ImageDestroy($img);
?>

yl
Simple function to create border for jpg-images:
function createImageBorder($imgName){
$img     =  substr($imgName, 0, -4); // remove fileExtension
$ext     = ".jpg";
$quality = 95;
$borderColor = 255;  // 255 = white

/*
a                         b
+-------------------------+
|                          
|          IMAGE          
|                          
+-------------------------+
c                         d  
*/

$scr_img = imagecreatefromjpeg($img.$ext);
$width   = imagesx($scr_img);
$height  = imagesy($scr_img);
 
// line a - b
$abX  = 0;
$abY  = 0;
$abX1 = $width;
$abY1 = 0;

// line a - c
$acX  = 0;
$acY  = 0;
$acX1 = 0;
$acY1 = $height;

// line b - d
$bdX  = $width-1;
$bdY  = 0;
$bdX1 = $width-1;
$bdY1 = $height;

// line c - d
$cdX  = 0;
$cdY  = $height-1;
$cdX1 = $width;
$cdY1 = $height-1;

  // DRAW LINES
imageline($scr_img,$abX,$abY,$abX1,$abY1,$borderColor);
imageline($scr_img,$acX,$acY,$acX1,$acY1,$borderColor);
imageline($scr_img,$bdX,$bdY,$bdX1,$bdY1,$borderColor);
imageline($scr_img,$cdX,$cdY,$cdX1,$cdY1,$borderColor);

 // create copy from image
imagejpeg($scr_img, $img."_border.jpg", $quality);
imagedestroy($scr_img);
 }

createImageBorder("myfile.jpg");

xxxoldsaltxxx
Script to draw a grid of lines, which make the entire side of the picture look like a quarter circle.. very cool :)
<?php
$img_disp = imagecreate(1000,1000);
$backcolor = imagecolorallocate($img_disp,0,0,0);
imagefill($img_disp,0,0,$backcolor);
$textcolor = imagecolorallocate($img_disp,255,0,0);
$x1 = 0;
$y1 = 0;
$x2 = 0;
$y2 = 1000;
for(;;){
$y1 = $y1 + 20;
$x2 = $x2 + 20;
imageline($img_disp,$x1,$y1,$x2,$y2,$textcolor);
if ($y1 == 1000){
break;
}
}
header("Content-type: image/png");
imagepng($img_disp); // Draw the image
imagedestroy($img_disp); // Delete the image from the server's memory
?>

darren
It does work (With a bit of editing)
save the following as graph.php (You dont need any directorys)
<?php
Header("Content-type: image/png");
$picWidth=360*2;
$picHeight=200;
$pic=ImageCreate($picWidth+1,$picHeight+1);
$cWhite=ImageColorAllocate($pic,255,255,255);
ImageFilledRectangle($pic,0,0,$picWidth+1,$picHeight+1,$cWhite);
$cRed=ImageColorAllocate($pic,255,0,0);
$cBlue=ImageColorAllocate($pic,0,0,255);
$curX=0;
$curY=$picHeight;
for($pt=0;$pt<$picWidth;$pt++){
$newX=$curX+1;
$newY=($picHeight/2)+(cos(deg2rad($newX))*($picHeight/2));
ImageLine($pic,$curX,$curY,$newX,$newY,$cRed);
$curX=$newX;
$curY=$newY;
}
$curX=0;
$curY=$picHeight/2;
for($pt=0;$pt<$picWidth;$pt++){
$newX=$curX+1;
$newY=($picHeight/2)+(sin(deg2rad($newX))*($picHeight/2));
ImageLine($pic,$curX,$curY,$newX,$newY,$cBlue);
$curX=$newX;
$curY=$newY;
}
$cBlack=ImageColorAllocate($pic,0,0,0);
ImageLine($pic,0,0,0,$picHeight,$cBlack);
ImageLine($pic,0,$picHeight/2,$picWidth,$picHeight/2,$cBlack);
ImagePNG($pic);
ImageDestroy($pic);
?>

21-oct-2005 03:30
imageline coordinate variables are documented as int ,  a value in decimal format will be truncated.
This may be useful when, for example, applying a non-integer scaling factor in generating an image.
Care should be taken to ensure this does not create significant errors that affect the quality of the image. For example :
<?php
$x=0.00000000001;$y=100;
imageline($img,0,0,0,$y+$x);
imageline($img,0,0,0,$y-$x);
?>
the first line will be straight , the second will have a step. Use round() where appropriate.

jonathan w.
I've modified the previous entry for drawing on a polar coordinate system to better represent angles based on a 360º whole circle bearing.
<?php
function imagepolarline($image,$x1,$y1,$length,$angle,$color)
{
   $x2 = $x1 + sin( deg2rad($angle) ) * $length;
   $y2 = $y1 + cos( deg2rad($angle+180) ) * $length;
   imageline($image,$x1,$y1,$x2,$y2,$color);
}
?>

ian b
Here's a function to plot a line on a polar coordinate system:
<?php
function imagepolarline($image,$x1,$y1,$length,$angle,$color)
{
$x2 = $x1 + sin( deg2rad($angle+90) ) * $length;
$y2 = $y1 + cos( deg2rad($angle+90) ) * $length;
imageline($image,$x1,$y1,$x2,$y2,$color);
}
?>
x1,y1 are the coordinates for the central point. If you want the orientation to be like a compass i.e. 90 degrees = East, 180 = South etc, then use the following:
$x2 = $x1 + cos( deg2rad($angle-90)) * $length;
$y2 = $y1 + sin( deg2rad($angle-90)) * $length;

d
Here my function do clear all problems. With this, you can draw firstly smooth lines (basic code adapted from code_couturier at graffiti dot net, with some performance changes). The special is, you can define the alpha-value of the line (0 = normal smooth line, 127 = fully transparent). Change whatever you want to make it better, but post your results ;)
<?php
/**
* function imageSmoothAlphaLine() - version 1.0
* Draws a smooth line with alpha-functionality
*
* @param   ident    the image to draw on
* @param   integer  x1
* @param   integer  y1
* @param   integer  x2
* @param   integer  y2
* @param   integer  red (0 to 255)
* @param   integer  green (0 to 255)
* @param   integer  blue (0 to 255)
* @param   integer  alpha (0 to 127)
*
* @access  public
*
* @author  DASPRiD <d@sprid.de>
*/
function imageSmoothAlphaLine ($image, $x1, $y1, $x2, $y2, $r, $g, $b, $alpha=0) {
 $icr = $r;
 $icg = $g;
 $icb = $b;
 $dcol = imagecolorallocatealpha($image, $icr, $icg, $icb, $alpha);
 
 if ($y1 == $y2 || $x1 == $x2)
   imageline($image, $x1, $y2, $x1, $y2, $dcol);
 else {
   $m = ($y2 - $y1) / ($x2 - $x1);
   $b = $y1 - $m * $x1;
   if (abs ($m) <2) {
     $x = min($x1, $x2);
     $endx = max($x1, $x2) + 1;
     while ($x < $endx) {
       $y = $m * $x + $b;
       $ya = ($y == floor($y) ? 1: $y - floor($y));
       $yb = ceil($y) - $y;
 
       $trgb = ImageColorAt($image, $x, floor($y));
       $tcr = ($trgb >> 16) & 0xFF;
       $tcg = ($trgb >> 8) & 0xFF;
       $tcb = $trgb & 0xFF;
       imagesetpixel($image, $x, floor($y), imagecolorallocatealpha($image, ($tcr * $ya + $icr * $yb), ($tcg * $ya + $icg * $yb), ($tcb * $ya + $icb * $yb), $alpha));
 
       $trgb = ImageColorAt($image, $x, ceil($y));
       $tcr = ($trgb >> 16) & 0xFF;
       $tcg = ($trgb >> 8) & 0xFF;
       $tcb = $trgb & 0xFF;
       imagesetpixel($image, $x, ceil($y), imagecolorallocatealpha($image, ($tcr * $yb + $icr * $ya), ($tcg * $yb + $icg * $ya), ($tcb * $yb + $icb * $ya), $alpha));
 
       $x++;
     }
   } else {
     $y = min($y1, $y2);
     $endy = max($y1, $y2) + 1;
     while ($y < $endy) {
       $x = ($y - $b) / $m;
       $xa = ($x == floor($x) ? 1: $x - floor($x));
       $xb = ceil($x) - $x;
 
       $trgb = ImageColorAt($image, floor($x), $y);
       $tcr = ($trgb >> 16) & 0xFF;
       $tcg = ($trgb >> 8) & 0xFF;
       $tcb = $trgb & 0xFF;
       imagesetpixel($image, floor($x), $y, imagecolorallocatealpha($image, ($tcr * $xa + $icr * $xb), ($tcg * $xa + $icg * $xb), ($tcb * $xa + $icb * $xb), $alpha));
 
       $trgb = ImageColorAt($image, ceil($x), $y);
       $tcr = ($trgb >> 16) & 0xFF;
       $tcg = ($trgb >> 8) & 0xFF;
       $tcb = $trgb & 0xFF;
       imagesetpixel ($image, ceil($x), $y, imagecolorallocatealpha($image, ($tcr * $xb + $icr * $xa), ($tcg * $xb + $icg * $xa), ($tcb * $xb + $icb * $xa), $alpha));
 
       $y ++;
     }
   }
 }
} // end of 'imageSmoothAlphaLine()' function
?>

kramesch_nospam_
Here is a simple code to draw a line with an arbitrary stroke. The parameter aStroke is treated as a cyclic boolean array where true equals "set a point"
e.g. $aDotStroke = array(true,false);
function ImageStrokeLine($im,$x1,$y1,$x2,$y2,$farbe, $aStroke)
 {
   $deltax = abs($x2 - $x1);        
   $deltay = abs($y2 - $y1);        
   $x = $x1;                      
   $y = $y1;                      
   
   if ($x2 >= $x1)                
   {
     $xinc1 = 1;
     $xinc2 = 1;
   }
   else                          
   {
     $xinc1 = -1;
     $xinc2 = -1;
   }
   
   if ($y2 >= $y1)                
   {
     $yinc1 = 1;
     $yinc2 = 1;
   }
   else                          
   {
     $yinc1 = -1;
     $yinc2 = -1;
   }
   
   if ($deltax >= $deltay)  
   {
     $xinc1 = 0;                
     $yinc2 = 0;                
     $den = $deltax;
     $num = $deltax / 2;
     $numadd = $deltay;
     $numpixels = $deltax;
   }
   else                          
   {
     $xinc2 = 0;            
     $yinc1 = 0;            
     $den = $deltay;
     $num = $deltay / 2;
     $numadd = $deltax;
     $numpixels = $deltay;
   }
   
   for ($curpixel = 0; $curpixel <= $numpixels; $curpixel++)
   {
     if ($iStrokeCount >= count($aStroke))
     {
       $iStrokeCount = 0;
     }
 
     if ($aStroke[$iStrokeCount++])
     {
       ImageSetPixel($im,$x, $y,$farbe);            
     }
     $num += $numadd;            
     if ($num >= $den)            
     {
       $num -= $den;              
       $x += $xinc1;              
       $y += $yinc1;              
     }
     $x += $xinc2;                
     $y += $yinc2;                
   }
 }

fatpratmatt
Here is a function which draws lines that cross at a specific point [It may need some tweaking]:
<?php
// Image Cross by Matt Evans
// $im - image resource
// $x - x coordinate where the lines should cross
// $y - y coordinate where the lines should cross
// $size - the length of each line
// $colour - the colour of the cross
function imagecross($im, $x, $y, $size = 5, $colour) {
imageline($im, $x+$size/2, $y+$size/2, $x-$size/2, $y-$size/2, $colour);
imageline($im, $x-$size/2, $y+$size, $x+$size/2, $y-$size, $colour);
}
// Example
imagecross($im, 50, 50, 5, $crosscolour);
?>

ruturaj_v
here is a function that helps you create arrows...
<?php
function get_arrowheads ($x1, $y1, $x2, $y2, $arrhead, $arrang) {
   $debug = false;
   
   define("INFINITE", 'INFINITE');
   if (($x2-$x1)==0) {
       if ($y1 == 0) {
           $slope = 0;
       } else {
           $slope = INFINITE;
       }
   } else {
       $slope = -($y2-$y1)/($x2-$x1);
   }
   //$slope = number_format($slope, 2, '.','');
   if ($slope == 'INFINITE') {
       $ang = 90;
   } else {
       $ang = atan ($slope);
       $ang = ($ang * 180)/pi();
   }
   //$ang = number_format($ang, 2, '.', '');
   //echo ($ang);
   //exit;
   //convert the angle
   $arrang1 = ($ang - $arrang);
   $arrangdeg1 = ($ang - $arrang);
   //echo ($arrang1);exit;
   $arrang1 = ($arrang1*pi())/180;
   $arrang2 = ($ang + $arrang);
   $arrangdeg2 = ($ang + $arrang);
   $arrang2 = ($arrang2*pi())/180;
   //echo ($arrang1);
   $arx1 = (floor(cos($arrang1)*$arrhead));
   $ary1 = (floor(sin($arrang1)*$arrhead));
   $arx2 = (floor(cos($arrang2)*$arrhead));
   $ary2 = (floor(sin($arrang2)*$arrhead));
   if ($debug) {
       echo ("Values of arx1.. before add/sub</br>");
       echo ("$arx1,$ary1&nbsp;&nbsp;&nbsp;$arx2,$ary2</br>");
   }
   if ($ang==0) {
       if ($x2 > $x1) {
           $arx1 = $x2 - $arx1;    $ary1 = $y2 - $ary1;
           $arx2 = $x2 - $arx2;    $ary2 = $y2 - $ary2;
       } elseif ($x2 < $x1) {
           $arx1 = $x2 + $arx1;    $ary1 = $y2 - $ary1;
           $arx2 = $x2 + $arx2;    $ary2 = $y2 - $ary2;
       }
   }
   if ($ang > 0 && $ang < 90) {
       if (($x2 > $x1) && ($y2 < $y1)) {
           $arx1 = $x2 - $arx1;    $ary1 = $y2 + $ary1;
           $arx2 = $x2 - $arx2;    $ary2 = $y2 + $ary2;
       } elseif (($x2 < $x1) && ($y2 > $y1)) {
           $arx1 = $x2 + $arx1;    $ary1 = $y2 - $ary1;
           $arx2 = $x2 + $arx2;    $ary2 = $y2 - $ary2;
       }
   }
   if ($ang==90) {
       if (($y2 > $y1)) {
           $arx1 = $x2 - $arx1;    $ary1 = $y2 - $ary1;
           $arx2 = $x2 - $arx2;    $ary2 = $y2 - $ary2;
       } elseif (($y2 < $y1)) {
           $arx1 = $x2 - $arx1;    $ary1 = $y2 + $ary1;
           $arx2 = $x2 - $arx2;    $ary2 = $y2 + $ary2;
       }
   }
   if ($ang > -90 && $ang < 0) {
       if (($x2 > $x1) && ($y2 > $y1)) {
           $arx1 = $x2 - $arx1;    $ary1 = $y2 + $ary1;
           $arx2 = $x2 - $arx2;    $ary2 = $y2 + $ary2;
       } elseif (($x2 < $x1) && ($y2 < $y1)) {
           $arx1 = $x2 + $arx1;    $ary1 = $y2 - $ary1;
           $arx2 = $x2 + $arx2;    $ary2 = $y2 - $ary2;
       }
   }
   if ($debug) {
       echo ("Angle of line is (".$ang*180/pi().")</br>");
       echo ("Angle of line1 is $arrangdeg1</br>");
       echo ("Angle of line2 is $arrangdeg2</br>");
       echo ("$arx1,$ary1&nbsp;&nbsp;&nbsp;$x2,$y2</br>");
       echo ("$arx2,$ary2&nbsp;&nbsp;&nbsp;$x2,$y2");
       exit;
   }
   
   $array_arrows = array (
'x1' =>$arx1,
'y1' => $ary1,
'x2' => $arx2,
'y2' => $ary2
);
   return $array_arrows;
}
$x1 = 200; $y1 = 200;
$x2 = 400; $y2 = 100;
$arrhead = 15; //10px
$arrang = 10; //10 deg
$ar_arrws = get_arrowheads ($x1, $y1, $x2, $y2, $arrhead, $arrang);
$im  = imagecreate (400, 400);
$w   = imagecolorallocate ($im, 255, 255, 255);
$red = imagecolorallocate ($im, 255, 0, 0);
//creates the base line
imageline ($im, $x1, $y1, $x2, $y2, $green);
imageline ($im, $x1+1, $x2+1, $y1+1, $y2+1, $red);
imageline ($im, $x2, $y2, $ar_arrws['x1'], $ar_arrws['y1'], $green);
imageline ($im, $x2, $y2, $ar_arrws['x2'], $ar_arrws['y2'], $green);
?>

nanobot
Here is a function for making antialiased lines:
function imagesmoothline ( $image , $x1 , $y1 , $x2 , $y2 , $color )
{
 $colors = imagecolorsforindex ( $image , $color );
 if ( $x1 == $x2 )
 {
  imageline ( $image , $x1 , $y1 , $x2 , $y2 , $color ); // Vertical line
 }
 else
 {
  $m = ( $y2 - $y1 ) / ( $x2 - $x1 );
  $b = $y1 - $m * $x1;
  if ( abs ( $m ) <= 1 )
  {
   $x = min ( $x1 , $x2 );
   $endx = max ( $x1 , $x2 );
   while ( $x <= $endx )
   {
    $y = $m * $x + $b;
    $y == floor ( $y ) ? $ya = 1 : $ya = $y - floor ( $y );
    $yb = ceil ( $y ) - $y;
    $tempcolors = imagecolorsforindex ( $image , imagecolorat ( $image , $x , floor ( $y ) ) );
    $tempcolors['red'] = $tempcolors['red'] * $ya + $colors['red'] * $yb;
    $tempcolors['green'] = $tempcolors['green'] * $ya + $colors['green'] * $yb;
    $tempcolors['blue'] = $tempcolors['blue'] * $ya + $colors['blue'] * $yb;
    if ( imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) == -1 ) imagecolorallocate ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] );
    imagesetpixel ( $image , $x , floor ( $y ) , imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) );
    $tempcolors = imagecolorsforindex ( $image , imagecolorat ( $image , $x , ceil ( $y ) ) );
    $tempcolors['red'] = $tempcolors['red'] * $yb + $colors['red'] * $ya;
     $tempcolors['green'] = $tempcolors['green'] * $yb + $colors['green'] * $ya;
    $tempcolors['blue'] = $tempcolors['blue'] * $yb + $colors['blue'] * $ya;
    if ( imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) == -1 ) imagecolorallocate ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] );
    imagesetpixel ( $image , $x , ceil ( $y ) , imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) );
    $x ++;
   }
  }
  else
  {
   $y = min ( $y1 , $y2 );
   $endy = max ( $y1 , $y2 );
   while ( $y <= $endy )
   {
    $x = ( $y - $b ) / $m;
    $x == floor ( $x ) ? $xa = 1 : $xa = $x - floor ( $x );
    $xb = ceil ( $x ) - $x;
    $tempcolors = imagecolorsforindex ( $image , imagecolorat ( $image , floor ( $x ) , $y ) );
    $tempcolors['red'] = $tempcolors['red'] * $xa + $colors['red'] * $xb;
    $tempcolors['green'] = $tempcolors['green'] * $xa + $colors['green'] * $xb;
    $tempcolors['blue'] = $tempcolors['blue'] * $xa + $colors['blue'] * $xb;
    if ( imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) == -1 ) imagecolorallocate ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] );
    imagesetpixel ( $image , floor ( $x ) , $y , imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) );
    $tempcolors = imagecolorsforindex ( $image , imagecolorat ( $image , ceil ( $x ) , $y ) );
    $tempcolors['red'] = $tempcolors['red'] * $xb + $colors['red'] * $xa;
    $tempcolors['green'] = $tempcolors['green'] * $xb + $colors['green'] * $xa;
    $tempcolors['blue'] = $tempcolors['blue'] * $xb + $colors['blue'] * $xa;
    if ( imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) == -1 ) imagecolorallocate ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] );
    imagesetpixel ( $image , ceil ( $x ) , $y , imagecolorexact ( $image , $tempcolors['red'] , $tempcolors['green'] , $tempcolors['blue'] ) );
    $y ++;
   }
  }
 }
}
EDITOR: My previous code contained bugs. Please use this one instead.

lionel van bemten
here is a code to draw a "degraded" ... :
<?
header("Content-type : image/jpeg");
$image = @ImageCreate(200, 100)
 or die ("Erreur de création de l'image");
$lignes_colorees = 1;
$couleur_fond = ImageColorAllocate($image, 255, 255, 255);
$rouge_depart = 100;
$vert_depart = 255;
$bleu_depart = 0;
$rouge_fin = 0;
$vert_fin = 100;
$bleu_fin = 0;
$lignes = 100; //nb de lignes de l'image
$vert_diff = $vert_fin - $vert_depart;
$vert1 = $vert_diff / $lignes;
$bleu_diff = $bleu_fin - $bleu_depart;
$bleu1 = $bleu_diff / $lignes;
$rouge_diff = $rouge_fin - $rouge_depart;
$rouge1 = $rouge_diff / $lignes;
while ($lignes_colorees <= 100)
{
$rouge2 = $lignes_colorees * $rouge1; $rouge3 = $rouge_depart + $rouge2;
$rouge = round($rouge3);

$vert2 = $lignes_colorees * $vert1;
$vert3 = $vert_depart + $vert2;
$vert = round($vert2);

$bleu2 = $lignes_colorees * $bleu1;
$bleu3 = $bleu_depart + $bleu2;
$bleu = round($bleu2);

$y1 = $lignes_colorees;
$y2 = $lignes_colorees;
$x1 = 1; $x2 = 200;

$couleur = ImageColorAllocate($image, $rouge, $vert, $bleu);
//dessine la ligne
ImageLine($image, $x1, $y1, $x2, $y2, $couleur); $lignes_colorees ++;
}
//dessine l'image
ImageJpeg($image);
?>

admin
example of a Simple grid...
bool imagegrid ( resource $image, int $width, int $Height, int $size, mixed $color )
<?php
Header("Content-type: image/png");
$Width=450;
$Height=450;
$img = ImageCreateTrueColor($Width, $Height);
$bg = imagecolorallocate($img, 255, 255, 255);
imagefill($img, 0, 0, $bg);
$grid = imagecolorallocate($img, 225, 245, 249);
imagesetstyle($img, array($bg, $grid));
imagegrid($img, $Width, $Height, 10, IMG_COLOR_STYLED);
//makegrid($img, $Width, $Height, 10, $grid);
ImagePNG($img);
ImageDestroy($img);
function imagegrid($image, $w, $h, $s, $color)
{
for($iw=1; $iw<$w/$s; $iw++){imageline($image, $iw*$s, 0, $iw*$s, $w, $color);}
for($ih=1; $ih<$h/$s; $ih++){imageline($image, 0, $ih*$s, $w, $ih*$s, $color);}
}
?>

mueller
an algorithm to draw a bezier spline
<?php
$segmentos =30;
$x=array(0,10,80,30);
$y=array(0,10,40,50);
function bezier($p,$steps){
$t = 1 / $steps;
$temp = $t * $t;
$ret = array();
$f = $p[0];
$fd = 3 * ($p[1] - $p[0]) * $t;
$fdd_per_2=3*($p[0]-2*$p[1]+$p[2])*$temp;
$fddd_per_2=3*(3*($p[1]-$p[2])+$p[3]-$p[0])*$temp*$t;
$fddd = $fddd_per_2 + $fddd_per_2;
$fdd = $fdd_per_2 + $fdd_per_2;
$fddd_per_6 = $fddd_per_2 * (1.0 / 3);
for ($loop=0; $loop<$steps; $loop++) {
array_push($ret,$f);
   $f = $f + $fd + $fdd_per_2 + $fddd_per_6;
   $fd = $fd + $fdd + $fddd_per_2;
   $fdd = $fdd + $fddd;
   $fdd_per_2 = $fdd_per_2 + $fddd_per_2;
}
return $ret;
}
$by = bezier($y,$segmentos);
$bx = bezier($x,$segmentos);
header ("Content-type: image/jpeg");
$tam = 200;
$im = imagecreate($tam,$tam);
$background_color = imagecolorallocate ($im, 200, 200, 200);
$tc = imagecolorallocate ($im, 233, 14, 91);
for($i=0;$i<$segmentos-1;$i++)
imageline($im,$bx[$i],$tam-$by[$i],$bx[$i+1],$tam-$by[$i+1],$tc);
imagejpeg($im);
imagedestroy($im);
?>

tyron
// Here's a function for drawing a rotated gradient Rectangle (based on a previous note)
// Create An Image 255x255
$img = ImageCreateTrueColor(255, 255);
GradientRect($img,50,50,80,80,30);
ImagePng($img,"test.png");
ImageDestroy($img);
echo "
<img src=\"test.png\">";
function GradientRect($img, $x1, $y1, $x2, $y2, $wdt) {
 $alpha = atan2($y2-$y1,$x2-$x1);
 $real_wdt = $wdt*sin($alpha);
 $real_hgt = $wdt*cos($alpha);
 echo "real wdt:".$real_wdt;
 echo "
real hgt:".$real_hgt;
 echo "
angle: ".($angle*180/pi());
 $plotD = 0;
 $i=0;
 $dy = $real_hgt/$wdt;
 $dx = $real_wdt/$wdt;
 $drgb= 256/$wdt;
 while($i++ < $wdt) {
   // Draw a line and move it down and make it lighter to get the gradient effect
   ImageLine($img, $x1-$i*$dx, $y1+$i*$dy, $x2-$i*$dx, $y2+$i*$dy, ImageColorAllocate($img, $i*$drgb, 0, 0));
   ImageLine($img, $x1-$i*$dx+1, $y1+$i*$dy, $x2-$i*$dx+1, $y2+$i*$dy, ImageColorAllocate($img, $i*$drgb, 0, 0));
 }
}

ajreading
<?php
// An easy bit of code showing how you can use the ImageLine() function to create gradients
// Create An Image 255x255
$img = ImageCreateTrueColor(255, 255);
$plotD = 0;
while($plotD < 256)
{
   // Draw a line and move it down and make it lighter to get the gradient effect
   ImageLine($img, 0, $plotD , 255, $plotD, ImageColorAllocate($img, $plotD, $plotD, $plotD));
   $plotD++;
}
Header("Content-type: image/png");
ImagePng($img);
ImageDestroy($img);
?>

code_couturier
# antialiased lines with true-type-fonts !?
# yip, it works - not very good - but faster
# (below 3 sec) than other routines (~7 sec)
# i saw here.
# the antialiased effect is minimal and only
# at the top of the line - but, as better as
# nothing ;)
# here is a drawLine routine from Logan Gunthorpe
# (logang at deltatee dot com) posted by nanobot at chipx86 dot com
# on php.net and enhanced/optimized by myself :)
function drawSoftLine ($image, $x1, $y1, $x2, $y2, $r,$g,$b) {
$fontfile="arial.ttf"; # the font for the dot
$str="·" ; # the point_char for the dot
$size=12; # the point for the dot_size
$color = ImageColorAllocate ($image, $r,$g,$b);
if ($x2 == $x1) {
$tmp = $x1; $x1 = $y1; $y1 = $tmp;
$tmp = $x2; $x2 = $y2; $y2 = $tmp;
$swapx = true;
}
$m = (float)(( $y2 - $y1 ) / ( $x2 - $x1 ));
$b = (float)($y1 - $m*$x1);
$strx = min ( $x1 , $x2 );
$endx = max ( $x1 , $x2 );
$x=(int)0;
# the original loop was based on one for_loop
# with the if_swap inside. to speed up this loop
# i double it, to keep off the permanent if_call's.
if (!$swapx) {
for ($x = $strx; $x <= $endx; $x++) {
  $y = (int)($m*$x + $b);  
  imagettftext($image, $size, 0, $x, $y,
  $color, $fontfile,$str);
}
} else {
for ($x = $strx; $x <= $endx; $x++) {
  $y = (int)($m*$x + $b);  
  imagettftext($image, $size, 0, $y, $x,
  $color, $fontfile,$str);
 }
}
}

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