说明

bool imageline ( resource image, int x1, int y1, int x2, int y2, int color )

imageline() 用 color 颜色在图像 image 中从坐标 x1，y1 到 x2，y2（图像左上角为 0, 0）画一条线段。

例子 1. 画一条粗线 <?php function imagelinethick($image, $x1, $y1, $x2, $y2, $color, $thick = 1) {     /* 下面两行只在线段直角相交时好使     imagesetthickness($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); } ?>

参见 imagecreatetruecolor() 和 imagecolorallocate()。