PHP怎么生成缩略图_PHP批量生成高清缩略图功能

function generateThumbnail($sourcePath, $destinationPath, $targetWidth, $targetHeight, $quality = 85) {
    // 获取图片信息
    $imageInfo = getimagesize($sourcePath);
    if (!$imageInfo) {
        // 实际应用中需要更详细的错误日志
        error_log("无法获取图片信息: " . $sourcePath);
        return false;
    }

    $originalWidth = $imageInfo[0];
    $originalHeight = $imageInfo[1];
    $mime = $imageInfo['mime'];

    // 根据MIME类型创建原始图片资源
    switch ($mime) {
        case 'image/jpeg':
            $sourceImage = imagecreatefromjpeg($sourcePath);
            break;
        case 'image/png':
            $sourceImage = imagecreatefrompng($sourcePath);
            break;
        case 'image/gif':
            $sourceImage = imagecreatefromgif($sourcePath);
            break;
        default:
            error_log("不支持的图片格式: " . $mime);
            return false;
    }

    if (!$sourceImage) {
        error_log("无法创建图片资源: " . $sourcePath);
        return false;
    }

    // 计算缩放比例，保持宽高比
    $ratio = min($targetWidth / $originalWidth, $targetHeight / $originalHeight);
    $newWidth = $originalWidth * $ratio;
    $newHeight = $originalHeight * $ratio;

    // 创建新的空白图片资源
    $thumbnail = imagecreatetruecolor($newWidth, $newHeight);

    // 如果是PNG或GIF，需要保留透明度
    if ($mime == 'image/png' || $mime == 'image/gif') {
        imagealphablending($thumbnail, false);
        imagesavealpha($thumbnail, true);
        $transparent = imagecolorallocatealpha($thumbnail, 255, 255, 255, 127); // 白色透明背景
        imagefilledrectangle($thumbnail, 0, 0, $newWidth, $newHeight, $transparent);
    }

    // 重新采样并复制图像
    imagecopyresampled($thumbnail, $sourceImage, 0, 0, 0, 0, $newWidth, $newHeight, $originalWidth, $originalHeight);

    // 保存缩略图
    switch ($mime) {
        case 'image/jpeg':
            imagejpeg($thumbnail, $destinationPath, $quality);
            break;
        case 'image/png':
            // PNG的质量参数范围是0-9，9是最高压缩，0是无压缩
            // 这里将JPEG的0-100质量映射到PNG的0-9
            $pngQuality = round(($quality / 100) * 9);
            imagepng($thumbnail, $destinationPath, 9 - $pngQuality); // 9-x是因为imagepng的quality是压缩级别，数字越大压缩越大，质量越低
            break;
        case 'image/gif':
            imagegif($thumbnail, $destinationPath);
            break;
    }

    // 释放内存
    imagedestroy($sourceImage);
    imagedestroy($thumbnail);

    return true;
}

function batchGenerateThumbnails($sourceDir, $thumbDir, $targetWidth, $targetHeight, $quality = 85) {
    if (!is_dir($sourceDir)) {
        error_log("源目录不存在: " . $sourceDir);
        return false;
    }
    if (!is_dir($thumbDir) && !mkdir($thumbDir, 0755, true)) {
        error_log("无法创建目标目录: " . $thumbDir);
        return false;
    }

    // 设置PHP脚本最大执行时间，避免大批量处理时超时
    set_time_limit(0); 

    $files = scandir($sourceDir);
    $processedCount = 0;
    foreach ($files as $file) {
        if ($file == '.' || $file == '..') {
            continue;
        }

        $sourcePath = $sourceDir . '/' . $file;
        $destinationPath = $thumbDir . '/' . $file; // 可以根据需要修改缩略图的文件名，比如加前缀或后缀

        // 仅处理文件，跳过子目录
        if (!is_file($sourcePath)) {
            continue;
        }

        // 检查是否已经存在缩略图，避免重复生成
        // 实际应用中，可能还需要比较文件修改时间或者哈希值，判断源文件是否更新
        if (file_exists($destinationPath)) {
            // error_log("缩略图已存在，跳过: " . $destinationPath);
            continue; 
        }

        if (generateThumbnail($sourcePath, $destinationPath, $targetWidth, $targetHeight, $quality)) {
            $processedCount++;
            // error_log("成功生成缩略图: " . $destinationPath);
        } else {
            error_log("生成缩略图失败: " . $sourcePath);
        }
    }
    return $processedCount;
}

// 示例调用
// $sourceDirectory = '/path/to/original_images';
// $thumbnailDirectory = '/path/to/thumbnails';
// $processed = batchGenerateThumbnails($sourceDirectory, $thumbnailDirectory, 200, 200, 90);
// echo "批量处理完成，生成了 {$processed} 张缩略图。\n";