局域网屏幕监控软件 PHP 图像块增量传输算法解析

/**
 * 将图像分割为块并计算哈希
 * @param resource $image 图像资源
 * @return array 块哈希数组
 */
public function calculateBlockHashes($image) {
    $hashes = [];
    $width = imagesx($image);
    $height = imagesy($image);
    // 计算块的行数和列数
    $rows = ceil($height / $this->blockSize);
    $cols = ceil($width / $this->blockSize);
    for ($row = 0; $row < $rows; $row++) {
        for ($col = 0; $col < $cols; $col++) {
            // 计算当前块的区域
            $x = $col * $this->blockSize;
            $y = $row * $this->blockSize;
            $w = min($this->blockSize, $width - $x);
            $h = min($this->blockSize, $height - $y);
            // 创建块图像
            $block = imagecreatetruecolor($w, $h);
            imagecopy($block, $image, 0, 0, $x, $y, $w, $h);
            // 计算块哈希
            $hash = $this->calculateImageHash($block);
            $hashes[$row][$col] = $hash;
            imagedestroy($block);
        }
    }
    return $hashes;
}

/**
 * 比较两个块哈希数组，找出变化的块
 * @param array $oldHashes 旧的块哈希数组
 * @param array $newHashes 新的块哈希数组
 * @return array 变化的块坐标数组
 */
public function compareHashes($oldHashes, $newHashes) {
    $changedBlocks = [];
    $rows = max(count($oldHashes), count($newHashes));
    for ($row = 0; $row < $rows; $row++) {
        $cols = max(isset($oldHashes[$row])? count($oldHashes[$row]) : 0,
            isset($newHashes[$row])? count($newHashes[$row]) : 0);
        for ($col = 0; $col < $cols; $col++) {
            $oldHash = $oldHashes[$row][$col]?? '';
            $newHash = $newHashes[$row][$col]?? '';
            if ($oldHash!== $newHash) {
                $changedBlocks[] = ['row' => $row, 'col' => $col];
            }
        }
    }
    return $changedBlocks;
}

/**
 * 提取变化的块并发送到服务器
 * @param resource $image 图像资源
 * @param array $changedBlocks 变化的块坐标数组
 */
public function sendChangedBlocks($image, $changedBlocks) {
    if (empty($changedBlocks)) {
        return; // 没有变化的块
    }
    $width = imagesx($image);
    $height = imagesy($image);
    // 创建包含所有变化块的图像
    $combinedImage = imagecreatetruecolor($width, $height);
    imagefill($combinedImage, 0, 0, imagecolorallocate($combinedImage, 255, 255, 255));
    foreach ($changedBlocks as $block) {
        $row = $block['row'];
        $col = $block['col'];
        $x = $col * $this->blockSize;
        $y = $row * $this->blockSize;
        $w = min($this->blockSize, $width - $x);
        $h = min($this->blockSize, $height - $y);
        imagecopy($combinedImage, $image, $x, $y, $x, $y, $w, $h);
    }
    // 将变化的块数据发送到服务器
    $tempFile = tempnam(sys_get_temp_dir(),'screen_diff_');
    imagejpeg($combinedImage, $tempFile, $this->quality);
    $data = ['blocks' => $changedBlocks, 'image' => new CURLFile($tempFile)];
    $ch = curl_init($this->serverUrl);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($ch);
    if (curl_errno($ch)) {
        error_log("发送失败: ". curl_error($ch));
    }
    curl_close($ch);
    unlink($tempFile);
    imagedestroy($combinedImage);
}