Rive format: extract width/height dimensions from binary file

rive-format-extract-dimensions.php

<?php
// Open the binary file
$filename = 'file.riv';
$file = fopen($filename, 'rb');
if (!$file) {
    exit();  // Exit if file cannot be opened
}
// Read the first 4 bytes and check if it's 'RIVE'
$byte = fread($file, 4);
if ($byte !== 'RIVE') {
    echo "Not a valid Rive file\n";
    exit();  // Exit if it's not a RIVE file
}

$majorVersion = fread($file, 1); // Major version
$minorVersion = fread($file, 1); // Minor version

// convert to integer
$majorVersion = ord($majorVersion);
$minorVersion = ord($minorVersion);

echo "Rive File Version: $majorVersion.$minorVersion\n";

// Read the next byte (TOC)
$byte = fread($file, 1);

$properties = [
    'widths' => [],
    'heights' => []
];

$minValue = 1;
$maxValue = 10000;
$widths = [];
$heights = [];


// Read all objects until the returned byte is 0, which should be the last property
while (!feof($file)) {
    $value = null;

    // Advance the byte by 1
    $byte = fread($file, 1);

    if (!$byte) {
        break;  // Exit if end of file or empty byte
    }

    // Grab the property type
    $property = ord($byte);  // Convert the byte to an integer

    // Next 4 bytes are the property value
    if ($property == 7) { // width
        $value = unpack('f', fread($file, 4))[1]; // Read 4 bytes as a float
        if($value >= $minValue && $value <= $maxValue) {
            $widths[] = $value;
        }
    } elseif ($property == 8) { // height
        $value = unpack('f', fread($file, 4))[1]; // Read 4 bytes as a float
        if($value >= $minValue && $value <= $maxValue) {
            $heights[] = $value;
        }
    }
}

// Close the file
fclose($file);

// sort values by descending order
rsort($widths, SORT_NUMERIC);
rsort($heights, SORT_NUMERIC);

// return the properties (Width and Height)
if (isset($widths[0]) && isset($heights[0])) {
    return [
        'width' => $widths[0] ?? null,
        'height' => $heights[0] ?? null
    ];
} else {
    return null;
}

?>