WebP 图像元数据处理：PHP 支持与实践

<?php

/**
 * Adds EXIF metadata to a WebP image file.
 *
 * @param string $targetFile The path to the WebP image file.
 * @param string $exifData The binary EXIF data to add.
 * @return bool True on success, false on failure.
 */
function addExifToWebP(string $targetFile, string $exifData): bool
{
    $exifLength = strlen($exifData);

    // RIFF requires 16-bit alignment
    if ($exifLength % 2 == 1) {
        $exifData .= "\0";
        $exifLength++; // Update length after padding
    }

    $fileHandle = fopen($targetFile, 'r+');
    if (!$fileHandle) {
        return false; // Failed to open file for writing
    }

    fseek($fileHandle, 0, SEEK_END); // Go to end of file

    // Write EXIF chunk
    fwrite($fileHandle, 'EXIF'); // 4 bytes chunk ID
    fwrite($fileHandle, pack('V', $exifLength)); // 4 bytes of payload length
    fwrite($fileHandle, $exifData); // Actual data

    $fileSize = ftell($fileHandle); // Get new file size

    fseek($fileHandle, 4, SEEK_SET); // Go to 5th byte of file
    fwrite($fileHandle, pack('V', $fileSize - 8)); // Write 4 bytes, patching old filesize

    fclose($fileHandle); // Store everything

    return true;
}

// Example usage:
$targetWebP = 'target.webp';
$exifData = file_get_contents('source.jpg'); // Get EXIF data from a JPEG file

// Extract EXIF data from JPG using exif_read_data
$exif = exif_read_data('source.jpg');
if ($exif === false) {
    echo "No EXIF data found in source.jpg.\n";
} else {
    // Convert the EXIF data to a binary string (this is a simplified example)
    $exifData = serialize($exif); // Consider using a proper EXIF serialization library

    if (addExifToWebP($targetWebP, $exifData)) {
        echo "EXIF data added to $targetWebP successfully.\n";
    } else {
        echo "Failed to add EXIF data to $targetWebP.\n";
    }
}

?>