90 lines
2.2 KiB
Dart
90 lines
2.2 KiB
Dart
import 'dart:io';
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import 'package:path/path.dart';
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class Vips {
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String? vipsExecuteFile;
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final String cacheDir;
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Vips({this.vipsExecuteFile, required this.cacheDir});
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/// 生成图片预览（WebP 格式）
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///
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/// [imgPath] 原图路径
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/// [w] 预览图宽度（可选）
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/// [h] 预览图高度（可选）
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///
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/// 如果同时指定 [w] 和 [h]，图片将按比例缩放以适应指定尺寸
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Future<File> generatePreview(
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String imgPath, {
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int? w,
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int? h,
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}) async {
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// 生成缓存文件名：包含原图 hash 和尺寸信息
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final baseName = basename(imgPath).hashCode.toString();
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final sizeSuffix = _buildSizeSuffix(w, h);
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final imgOut = "$cacheDir/preview/$baseName$sizeSuffix.webp";
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final outFile = File(imgOut);
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// 缓存命中：直接返回已存在的预览图
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if (outFile.existsSync()) {
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return outFile;
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}
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// 确保缓存目录存在
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await outFile.parent.create(recursive: true);
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// 构建 vips 命令参数
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if (w != null || h != null) {
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final thumbnailArgs = <String>[
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"thumbnail",
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imgPath,
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imgOut,
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w?.toString() ?? "0",
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"--height",
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h?.toString() ?? "0",
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];
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final thumbnailResult = await Process.run("vips", thumbnailArgs);
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if (thumbnailResult.exitCode != 0) {
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print(thumbnailResult.stderr);
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throw Exception("vips thumbnail failed!");
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}
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return outFile;
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} else {
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// 不缩放，直接转换为 WebP 格式
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final args = <String>[
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"webpsave",
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imgPath,
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imgOut,
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"--Q",
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"80",
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"--effort",
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"6",
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"--smart-subsample",
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];
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final result = await Process.run("vips", args);
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if (result.exitCode == 0) {
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return outFile;
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}
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print(result.stderr);
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throw Exception("vips image transcode failed!");
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}
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}
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/// 构建尺寸后缀
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///
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/// 例如：
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/// - w=200, h=150 => "_200x150"
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/// - w=200, h=null => "_200x0"
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/// - w=null, h=150 => "_0x150"
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/// - w=null, h=null => ""
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String _buildSizeSuffix(int? w, int? h) {
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if (w == null && h == null) {
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return "";
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}
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return "_${w ?? 0}x${h ?? 0}";
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}
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}
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