SubtitleEdit/subtitleedit · error · InvalidOperationException

No bitmaps to write.

Error message

No bitmaps to write.

What it means

Thrown by ImageOutputWriter.WritePreservedBitmaps when the list of bitmap subtitle items is empty. This method re-exports already-bitmapped subtitle formats (e.g. re-encoding a Blu-ray sup or BDN-XML) — it needs at least one bitmap item to write a header and body. Zero items means there is nothing to preserve.

Source

Thrown at src/seconv/Core/ImageOutputWriter.cs:101

    /// <summary>
    /// Image-to-image variant: write a sequence of pre-rendered bitmaps (Blu-Ray .sup,
    /// VobSub, MKV PGS, DVB-sub) into <paramref name="handler"/> without going through
    /// <see cref="ImageRenderer"/>. Source dimensions baked into each
    /// <see cref="BitmapSubtitleLoader.BitmapSubtitleItem"/> override
    /// <see cref="ConversionOptions.Resolution"/> when present, so e.g. a 1920x1080
    /// Blu-Ray sup re-exports as 1920x1080 BDN-XML even if the CLI's default
    /// <c>--resolution</c> is something else.
    /// </summary>
    public static void WritePreservedBitmaps(
        IReadOnlyList<BitmapSubtitleLoader.BitmapSubtitleItem> items,
        string filePath,
        IExportHandler handler,
        ConversionOptions options)
    {
        if (items.Count == 0)
        {
            throw new InvalidOperationException("No bitmaps to write.");
        }

        var (defaultWidth, defaultHeight) = options.Resolution ?? (1920, 1080);

        var first = items[0];
        var firstParam = BuildPreservedParameter(first, 0, defaultWidth, defaultHeight, options);
        handler.WriteHeader(filePath, firstParam);

        for (var i = 0; i < items.Count; i++)
        {
            var item = items[i];
            var ip = BuildPreservedParameter(item, i, defaultWidth, defaultHeight, options);
            handler.CreateParagraph(ip);
            handler.WriteParagraph(ip);
            // We do NOT dispose item.Bitmap here — ownership stays with BitmapSubtitleItem;
            // the caller disposes the whole list when done. Disposing twice would crash.
        }
        handler.WriteFooter();

View on GitHub (pinned to 17a9f07487)

Solutions

1. Check items.Count > 0 before calling WritePreservedBitmaps and report to the user.
2. Investigate the BitmapSubtitleLoader step — if the source should contain bitmap items, verify the loader's parse path and warning output.
3. Skip the export when the source is legitimately empty.

Example fix

// before
ImageOutputWriter.WritePreservedBitmaps(items, outPath, handler, options);

// after
if (items.Count == 0)
    return;
ImageOutputWriter.WritePreservedBitmaps(items, outPath, handler, options);

if (items == null || items.Count == 0)
{
    Console.Error.WriteLine("No bitmap subtitle items to write.");
    return;
}

static bool HasBitmapItems(IReadOnlyList<BitmapSubtitleLoader.BitmapSubtitleItem> items) => items != null && items.Count > 0;

try { ImageOutputWriter.WritePreservedBitmaps(items, outPath, handler, options); }
catch (InvalidOperationException ex) when (ex.Message.Contains("No bitmaps to write"))
{ /* report empty bitmap list to user */ }

When it happens

Trigger: Calling WritePreservedBitmaps(items, filePath, handler, options) where items.Count == 0. Occurs when a bitmap subtitle source loaded zero items (e.g. a .sup/.xml file whose entries all failed parsing), or when an upstream filter produced an empty item list.

Common situations: Re-exporting a corrupt or empty Blu-ray sup / BDN-XML file whose bitmap entries were all rejected by the loader; a deserialized bitmap list that was cleared or never populated before the export call.

Related errors

• No paragraphs to render.
• Image-based formats require ConversionOptions
• No Blu-Ray sup subtitles found in: {filePath}
• No PGS subtitles in MKV track #{track.TrackNumber}.
• No VobSub subtitle packs in: {subPath}

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/5e7165cfb5f13ebe. Report an issue: GitHub.