342 lines
13 KiB
C#
342 lines
13 KiB
C#
using System.Drawing.Drawing2D;
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namespace WinFormsApp3
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{
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/// <summary>
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/// 本页视频下载列表：每个候选视频用 ffmpeg 抽 3 张间隔 5 秒的截图拼成预览条，
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/// 肉眼对比哪个是当前视频后勾选，选文件夹批量下载。
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/// 当前正在播放的那条默认勾上。
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/// </summary>
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public partial class VideoListForm : Form
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{
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private const int RowHeight = 124;
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private const int PreviewWidth = 496;
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private const int PreviewHeight = 100;
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private readonly Func<VideoCandidate, CancellationToken, Task<(Image? Image, string? Error)>> _previewFactory;
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private readonly List<VideoRow> _rows = new();
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private readonly CancellationTokenSource _loadCts = new();
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private int _generatedCount;
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private int _failedCount;
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/// <summary>点“下载选中”后带回的勾选候选（按列表顺序）。</summary>
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public List<VideoCandidate> SelectedCandidates { get; } = new();
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public VideoListForm(IReadOnlyList<VideoCandidate> candidates, IReadOnlyCollection<string> currentUrls,
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Func<VideoCandidate, CancellationToken, Task<(Image? Image, string? Error)>> previewFactory)
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{
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InitializeComponent();
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_previewFactory = previewFactory;
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BuildRows(candidates, currentUrls);
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}
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private void BuildRows(IReadOnlyList<VideoCandidate> candidates, IReadOnlyCollection<string> currentUrls)
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{
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int y = 8;
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foreach (VideoCandidate candidate in candidates)
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{
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bool isCurrent = currentUrls.Contains(candidate.Url);
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VideoRow row = new VideoRow(candidate, Describe(candidate, isCurrent), isCurrent)
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{
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Location = new Point(8, y),
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Width = Math.Max(620, pnlVideos.ClientSize.Width - 24),
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};
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row.CheckChanged += (_, _) => UpdateSelectionCount();
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_rows.Add(row);
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pnlVideos.Controls.Add(row);
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y += RowHeight + 6;
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}
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pnlVideos.Resize += (_, _) =>
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{
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foreach (VideoRow row in _rows)
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{
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row.Width = Math.Max(620, pnlVideos.ClientSize.Width - 24);
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}
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};
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UpdateSelectionCount();
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}
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/// <summary>
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/// 截图预览在后台生成（三条并发），生成一条刷新一条；
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/// 失败时把原因直接写在预览条上，不让界面一直停在“生成中…”。
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/// </summary>
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protected override async void OnShown(EventArgs e)
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{
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base.OnShown(e);
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if (_rows.Count == 0)
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{
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lblHint.Text = "本页没有可下载的视频";
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return;
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}
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SemaphoreSlim semaphore = new SemaphoreSlim(3);
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Task[] tasks = _rows.Select(async row =>
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{
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await semaphore.WaitAsync(_loadCts.Token);
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try
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{
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Image? preview = null;
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string? error = null;
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try
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{
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(preview, error) = await _previewFactory(row.Candidate, _loadCts.Token);
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}
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catch (OperationCanceledException)
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{
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PreviewLog.Write("预览任务被取消（列表已关闭）");
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return;
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}
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catch (Exception ex)
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{
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// 抽帧失败按“无预览”处理，勾选与下载不受影响
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error = ex.Message;
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}
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PreviewLog.Write($"预览回传 UI img={(preview != null ? "ok" : "null")} error={(error ?? "-")}");
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if (_loadCts.IsCancellationRequested || !IsHandleCreated || IsDisposed)
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{
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preview?.Dispose();
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return;
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}
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BeginInvoke(() =>
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{
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row.SetResult(preview, error);
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if (preview == null) _failedCount++;
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_generatedCount++;
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// 最后一行刷新时直接切到完成文案，不依赖 WhenAll 后续代码的时序
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lblHint.Text = _generatedCount < _rows.Count
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? $"截图生成中… {_generatedCount}/{_rows.Count}" +
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(_failedCount > 0 ? $"（{_failedCount} 条失败，原因见预览条）" : string.Empty)
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: (_failedCount == 0
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? "截图已生成，对比后勾选要下载的视频"
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: $"截图生成完毕（{_failedCount} 条失败，原因见预览条；不影响勾选下载）");
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});
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}
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finally
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{
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semaphore.Release();
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}
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}).ToArray();
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await Task.WhenAll(tasks);
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if (!IsDisposed && !_loadCts.IsCancellationRequested)
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{
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lblHint.Text = _failedCount == 0
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? "截图已生成，对比后勾选要下载的视频"
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: $"截图生成完毕（{_failedCount} 条失败，原因见预览条；不影响勾选下载）";
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}
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}
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protected override void OnFormClosed(FormClosedEventArgs e)
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{
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_loadCts.Cancel();
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_loadCts.Dispose();
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base.OnFormClosed(e);
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}
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private void UpdateSelectionCount()
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{
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btnDownload.Text = $"下载选中 ({_rows.Count(r => r.IsChecked)})";
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}
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private void btnDownload_Click(object sender, EventArgs e)
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{
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SelectedCandidates.Clear();
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SelectedCandidates.AddRange(_rows.Where(r => r.IsChecked).Select(r => r.Candidate));
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if (SelectedCandidates.Count == 0)
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{
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MessageBox.Show(this, "先勾选要下载的视频（看截图对比哪个是当前视频）。",
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"下载列表", MessageBoxButtons.OK, MessageBoxIcon.Information);
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return;
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}
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DialogResult = DialogResult.OK;
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}
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private static string Describe(VideoCandidate candidate, bool isCurrent)
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{
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List<string> tags = new List<string>();
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if (isCurrent) tags.Add("当前播放");
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if (candidate.PlaylistText != null) tags.Add("内存播放列表");
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else if (VideoDownloader.IsHlsUrl(candidate.Url)) tags.Add("m3u8");
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if (!string.IsNullOrEmpty(candidate.AudioUrl)) tags.Add("音频轨已配对·自动合并");
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if (tags.Count == 0) tags.Add("直链");
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string hostLine;
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try
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{
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Uri u = new Uri(candidate.Url);
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string last = Path.GetFileName(u.AbsolutePath);
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hostLine = last.Length > 0 ? $"{u.Host} … {last}" : u.Host;
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}
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catch
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{
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hostLine = candidate.Url.Length > 90 ? candidate.Url[..90] + "…" : candidate.Url;
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}
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return $"【{string.Join("】【", tags)}】\n{hostLine}";
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}
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/// <summary>
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/// 把抽到的 JPEG 帧横向拼成一条预览图（约 3×160 宽），供列表行显示。
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/// </summary>
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public static Image? ComposeFrames(List<byte[]> frames)
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{
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if (frames == null || frames.Count == 0) return null;
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List<Image> source = new List<Image>();
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foreach (byte[] frame in frames)
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{
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try
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{
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Image img = Image.FromStream(new MemoryStream(frame));
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source.Add(img);
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}
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catch
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{
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// 坏帧直接跳过
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}
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}
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if (source.Count == 0) return null;
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const int cellW = 160;
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const int gap = 8;
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int cellH = PreviewHeight - 4;
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var sizes = source.Select(img =>
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{
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int w = cellW;
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int h = Math.Max(1, (int)Math.Round((double)cellW * img.Height / img.Width));
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if (h > cellH)
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{
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h = cellH;
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w = Math.Max(1, (int)Math.Round((double)cellH * img.Width / img.Height));
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}
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return (w, h);
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}).ToList();
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int canvasW = source.Count * cellW + (source.Count - 1) * gap;
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int canvasH = sizes.Max(s => s.h);
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Bitmap strip = new Bitmap(canvasW, canvasH);
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using (Graphics g = Graphics.FromImage(strip))
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{
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g.Clear(Color.Black);
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g.InterpolationMode = InterpolationMode.HighQualityBicubic;
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for (int i = 0; i < source.Count; i++)
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{
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int x = i * (cellW + gap) + (cellW - sizes[i].w) / 2;
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int y = (canvasH - sizes[i].h) / 2;
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g.DrawImage(source[i], new Rectangle(x, y, sizes[i].w, sizes[i].h));
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}
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}
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foreach (Image img in source) img.Dispose();
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return strip;
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}
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/// <summary>
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/// 一行候选：勾选框 + 截图预览条 + 说明文字。
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/// </summary>
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private sealed class VideoRow : UserControl
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{
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private readonly CheckBox _check = new();
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private readonly PictureBox _preview = new();
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private readonly ToolTip _tip = new();
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public VideoCandidate Candidate { get; }
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public bool IsChecked => _check.Checked;
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public event EventHandler? CheckChanged;
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public VideoRow(VideoCandidate candidate, string description, bool isChecked)
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{
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Candidate = candidate;
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Height = RowHeight;
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Margin = new Padding(0);
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TableLayoutPanel layout = new TableLayoutPanel
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{
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Dock = DockStyle.Fill,
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ColumnCount = 3,
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RowCount = 1,
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};
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layout.ColumnStyles.Add(new ColumnStyle(SizeType.Absolute, 30F));
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layout.ColumnStyles.Add(new ColumnStyle(SizeType.Absolute, PreviewWidth + 8F));
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layout.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 100F));
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_check.Dock = DockStyle.None;
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_check.Anchor = AnchorStyles.Top;
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_check.Location = new Point(4, 6);
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_check.Checked = isChecked;
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_check.CheckedChanged += (_, _) => CheckChanged?.Invoke(this, EventArgs.Empty);
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_preview.Size = new Size(PreviewWidth, PreviewHeight);
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_preview.SizeMode = PictureBoxSizeMode.Zoom;
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_preview.BackColor = Color.FromArgb(28, 28, 28);
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_preview.Image = Placeholder();
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Label text = new Label
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{
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Dock = DockStyle.Fill,
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Padding = new Padding(8, 4, 4, 2),
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Text = description,
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TextAlign = ContentAlignment.TopLeft,
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};
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layout.Controls.Add(_check, 0, 0);
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layout.Controls.Add(_preview, 1, 0);
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layout.Controls.Add(text, 2, 0);
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Controls.Add(layout);
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}
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public void SetResult(Image? image, string? error)
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{
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_preview.Image?.Dispose();
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if (image != null)
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{
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_preview.Image = image;
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_tip.SetToolTip(_preview, string.Empty);
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}
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else
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{
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// 把失败原因直接画在预览条上，一眼能看出是超时还是防盗链
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string reason = string.IsNullOrWhiteSpace(error) ? "截图不可用" : error!;
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_preview.Image = Placeholder(reason);
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_tip.SetToolTip(_preview, reason);
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}
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}
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/// <summary>截图还没生成好（或生成失败）时行内显示的占位条。</summary>
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private static Image Placeholder(string? message = null)
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{
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Bitmap bmp = new Bitmap(PreviewWidth, PreviewHeight);
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using Graphics g = Graphics.FromImage(bmp);
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g.Clear(Color.FromArgb(28, 28, 28));
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using (var cellBrush = new SolidBrush(Color.FromArgb(56, 56, 56)))
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{
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for (int i = 0; i < 3; i++)
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{
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g.FillRectangle(cellBrush, i * 168, 0, 160, PreviewHeight);
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}
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}
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using Font font = new Font("Microsoft YaHei UI", 8F);
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string text = message ?? "截图生成中…";
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Color color = message == null ? Color.Gray : Color.FromArgb(230, 140, 90);
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// 失败原因可能较长，在预览条区域内自动换行
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var rect = new RectangleF(4, 4, PreviewWidth - 8, PreviewHeight - 8);
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using var format = new StringFormat { Trimming = StringTrimming.EllipsisCharacter, FormatFlags = StringFormatFlags.LineLimit };
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g.DrawString(text, font, new SolidBrush(color), rect, format);
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return bmp;
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}
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}
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}
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}
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