Calculating SVG bounding box using PHP with respect to curves

Question

I recently found this amazing class located here, and tried using it.

However, it only works with some of the basic functions such as move, horizontal line, and vertical line.

--

I have tried extending this existing class by adding additional checks (and changing the regex).

public static function fromPath($pathString) {
    preg_match_all('/([mlvhzc][^mlvhzc]*)/i', $pathString, $commands);
    $pt = array(0, 0);
    $bounds = new self();
    foreach ($commands[0] as $command) {
        preg_match_all('/((\+|-)?\d+(\.\d+)?(e(\+|-)?\d+)?)/i', $command, $matches);
        $i = 0;
        while ($i < count($matches[1])) {
            switch ($command[0]) {
                case 'm' :
                case 'l' :
                    $pt[0] += $matches[1][$i++];
                    $pt[1] += $matches[1][$i++];
                    break;
                case 'M' :
                case 'L' :
                    $pt[0] = $matches[1][$i++];
                    $pt[1] = $matches[1][$i++];
                    $last=$pt;
                    break;
                case 'v' :
                    $pt[1] += $matches[1][$i++];
                    break;
                case 'V' :
                    $pt[1] = $matches[1][$i++];
                    $last[1]=$pt[1];
                    break;
                case 'h' :
                    $pt[0] += $matches[1][$i++];
                    break;
                case 'H' :
                    $pt[0] = $matches[1][$i++];
                    $last[0]=$pt[0];
                    break;
                case 'z' :
                case 'Z' :
                    break;
                case 'c':
                    $pt[0] = $last[0]+$matches[1][4];
                    $pt[1] = $last[1]+$matches[1][5];
                    $last=$pt;
                    $i=count($matches[1]);
                    break;
                default :
                    throw new RuntimeException("Unhandled path command: " . $command[0]);
            }
            $bounds->extend($pt[0], $pt[1]);
        }

    }
    return $bounds;
}

I checked out the SVG manual and found out that 'c' only has 6 parameters, knowing that the last 2 is where the curve will end up at, I tried to extend the points based on that...

For the moment, my tests are based around this:

<svg xmlns="http://www.w3.org/2000/svg" width="109" height="109" viewBox="0 0 109 109">
<g style="fill:none;stroke:#000000;stroke-width:3;stroke-linecap:round;stroke-linejoin:round;">
    <path d="M32.25,41c1.25,0.62,3.12,0.67,5.5,0.5c7.12-0.5,19.12-2.5,24-3c0.99-0.1,2.62-0.25,3.75,0" />            
</g>

When run in the browser, Chrome reports that it's width to height ratio (because I know svg doesn't exactly have sizes), is around 5 to 6, however, when I find the ratio with my script, it's completely off.

I'd like to know if there's another svg class built that supports all the functions (C,c,Q,q,etc).

I know that there's a way to get the box by converting it into an image, but I feel that is inefficient, also there's getBBox in javascript, but I'd like to perform the calculations on the server.

Thanks for Reading!

Answer 1

Here is an example using imagick, it is actually two example in one since they cannot be run at the same time, uncomment one at the time:

$svg = '<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" width="109" height="109" viewBox="0 0 109 109">
<g style="fill:none;stroke:#000000;stroke-width:3;stroke-linecap:round;stroke-linejoin:round;">
    <path d="M32.25,41c1.25,0.62,3.12,0.67,5.5,0.5c7.12-0.5,19.12-2.5,24-3c0.99-0.1,2.62-0.25,3.75,0" />            
</g>
</svg>';

$im = new Imagick();
$im->readImageBlob($svg);
$im->trimImage (0);//This trims the unecessary blank space.

//This block gets the dimensions (comment this block before uncommenting the second example bellow)
$dimension = $im->getImageGeometry();
print_r('<pre>');
print_r($dimension);
die();


/*//Uncomment this block to view thw jpeg version of the svg
$im->setImageFormat("jpeg");
header("Content-Type: image/jpeg");
$thumbnail = $im->getImageBlob();
echo $thumbnail;
$im->clear();
$im->destroy();
//*/

Answer 2

Hermann's answer helped me a lot, but doesn't actually trim the SVG. Below is the first solution I came to based on his answer:

function getTrimmedSvg( $filePath )
{
    $image = new Imagick();
    $image->readImage( $filePath );
    $image->trimImage( 0 );

    $imagePage = $image->getImagePage();
    $dimensions = $image->getImageGeometry();

    $minXOut = $imagePage['x'];
    $minYOut = $imagePage['y'];
    $widthOut = $dimensions["width"];
    $heightOut = $dimensions["height"];

    $xml = simplexml_load_file( $filePath );

    $xml["viewBox"] = "$minXOut $minYOut $widthOut $heightOut";

    return $xml->asXML();
}

While this works most of the time, it doesn't work all of the time. After much fruitless effort trying to fix edge cases, I switched to using a nodejs command-line utility called svg-bounding-box (GitHub). This took care of all my edge cases. After installing svg-bounding-box globally on your server and/or development environment, you can use it in your code this way:

function getTrimmedSvg( $filePath )
{
    $xml = simplexml_load_file( $filePath );

    $xml["viewBox"] = shell_exec( "cat $filePath | svg-bounding-box" );

    return $xml->asXML();
}