在图像中画一条有厚度的线?

时间:2013-04-08 05:17:04

标签: php image line gd thickness

我想使用GD库在PHP中使用图像绘制厚度线。我在这个页面中找到了一些解决方案PHP: imageline - Manual但是当行的(x,y)位置改变时,它们似乎都没有正常工作。

我在页面中找到了3个功能

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);
}

function imagelinethick($image, $x1, $y1, $x2, $y2, $color, $thick = 1)
{
    if ($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);
    $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);
}

function imagelinethick1($image, $x1, $y1, $x2, $y2, $color, $thick = 1)
{
    imagesetthickness($image, $thick);
    imageline($image, $x1, $y1, $x2, $y2, $color);
}

我的测试用例是

header("Content-Type: image/png");
$image = @imagecreatetruecolor(500, 500) or die("Cannot initialize new GD image stream");
$color = imagecolorallocate($image, 255, 255, 255);

# Line thickness equals to 18 pixels
$thickness = 18;

# OK
dickelinie($image, 0, 0, 0, 500, $color, $thickness);

# Wrong: The thickness of the line is doubled
dickelinie($image, 200, 0, 200, 500, $color, $thickness);

# Wrong: The thickness of the line is halved
imagelinethick($image, 0, 0, 0, 500, $color, $thickness);

# OK
imagelinethick($image, 200, 0, 200, 500, $color, $thickness);

# Wrong: The thickness of the line is halved
imagelinethick1($image, 0, 0, 0, 500, $color, $thickness);

# OK
imagelinethick1($image, 200, 0, 200, 500, $color, $thickness);

imagepng($image);
imagedestroy($image);

有人可以告诉我有什么问题吗?

3 个答案:

答案 0 :(得分:0)

php.net的imageline示例#1是“画一条粗线”。它建议使用imagesetthickness或以下代码:

<?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);
}
?>

答案 1 :(得分:0)

您的一些测试用例是错误的。每个用x = 0渲染的测试用例都将被切成两半,因为例程将新的粗线放在给定的xy坐标上。因此,渲染线的一半在位图之外渲染并丢失。

鉴于您的测试用例存在一点缺陷,我们可以看到“dickelinie”方法总是使预期厚度加倍。

我仍然使用“dickelinie”方法渲染简单的模拟时钟,因为它可以满足我的需求。我只是将它的厚度减半,以确保它有效。我还在“dickelinie”方法的末尾添加了以下代码,以确保在被告知为:

时,生成的行被呈现为消除锯齿:
return imagepolygon($img,  $array, (count($array) / 2), $color);

如果你需要以不同的角度渲染线条,你会想要这个。

答案 2 :(得分:0)

这不是解决问题的最快方法,但我在我的项目中使用此功能:

function thickline( $img, $x1, $y1, $x2, $y2, $color, $thickness ) {
  $radius = $thickness * .5;
  $vx = $x2 - $x1;
  $vy = $y2 - $y1;
  $steps = ceil( .5 + max( abs($vx), abs($vy) ) );
  $vx /= $steps;
  $vy /= $steps;
  $x = $x1;
  $y = $y1;
  while( $steps --> 0 ) {
    imagefilledellipse( $img, $x, $y, $radius, $radius, $color );
    $x += $vx;
    $y += $vy;
  }
}

这个想法是在一条线的每个点上绘制一个圆圈。