NickeManarin/ScreenToGif · error · ArgumentException

Only 24 and 32 bpp images are supported.

Error message

Only 24 and 32 bpp images are supported.

What it means

Thrown by PixelUtil.LockBitsAndPad (WPF-based pixel utility) when the source BitmapSource has a Format with BitsPerPixel other than 24 or 32. This method reads raw pixel data via WriteableBitmap and only supports Bgr24/Bgra32/Rgb24/Rgba32 equivalent formats.

Solutions

1. Convert the BitmapSource to Bgr32 or Bgra32 using new FormatConvertedBitmap(source, PixelFormats.Bgra32, null, 0) before creating PixelUtil.
2. Use WriteableBitmap.CopyPixels with a Format conversion step.
3. Validate source.Format.BitsPerPixel before constructing PixelUtil and convert or reject.
4. Ensure screen capture code creates bitmaps in a supported format from the start.

Example fix

// before
Depth = _source.Format.BitsPerPixel;
if (Depth != 32 && Depth != 24)
    throw new ArgumentException("Only 24 and 32 bpp images are supported.");

// after: convert unsupported formats to Bgra32
if (Depth != 32 && Depth != 24)
{
    var converter = new FormatConvertedBitmap(_source, PixelFormats.Bgra32, null, 0);
    _source = BitmapFrame.Create(converter);
    Depth = 32;
}

if (source.Format.BitsPerPixel != 24 && source.Format.BitsPerPixel != 32)
{
    source = new FormatConvertedBitmap(source, PixelFormats.Bgra32, null, 0);
    source.Freeze();
}

static bool IsSupportedWpfFormat(BitmapSource src)
{
    return src.Format.BitsPerPixel == 24 || src.Format.BitsPerPixel == 32;
}

try
{
    pixelUtil.LockBitsAndPad();
}
catch (ArgumentException ex) when (ex.Message.Contains("bpp"))
{
    _source = (BitmapSource)new FormatConvertedBitmap(_source, PixelFormats.Bgra32, null, 0);
    pixelUtil.LockBitsAndPad();
}

When it happens

Trigger: LockBitsAndPad is called on a BitmapSource whose Format.BitsPerPixel is not 24 or 32 (e.g., Bgr555 = 16bpp, Gray8 = 8bpp, Rgba64 = 64bpp, Bgr101010 = 32bpp but different channel layout).

Common situations: Screen capture produced a 16-bit or indexed-color bitmap. User imported an image with an exotic pixel format. A WPF rendering operation returned a non-standard format bitmap. Animated cursor or icon converted to BitmapSource with low bit depth.

Related errors

• Only 8, 24 and 32 bpp images are supported.
• Invalid file format, expected PNG signature not found.
• It was not possible to get a list of known screens.
• Missing IHDR chunk.

AI-assisted analysis of NickeManarin/ScreenToGif@a4d0a67c21 (2026-08-13). Data as JSON: /api/errors/a6a14a095d46d185. Report an issue: GitHub.

Appendix: source

Thrown at ScreenToGif.Util/Codification/PixelUtil.cs:74

    /// <summary>
    /// Lock bitmap data.
    /// </summary>
    public void LockBits()
    {
        //Get width and height of bitmap.
        Width = _source.PixelWidth;
        Height = _source.PixelHeight;

        //Get total locked pixels count.
        var pixelCount = Width * Height;

        //Get source bitmap pixel format size.
        Depth = _source.Format.BitsPerPixel;
        ChannelsPerPixel = Depth / 8;

        if (Depth != 32 && Depth != 24)
            throw new ArgumentException("Only 24 and 32 bpp images are supported.");

        _data = new WriteableBitmap(_source);

        //Lock bitmap and return bitmap data.
        _data.Lock();

        /*
            https://doanvublog.wordpress.com/tag/32bpp/
            1,4,8 and 16bpp uses a color table.

            1bpp : 1 byte, 8 pixels, 2 colors
            4bpp : 1 byte, 2 pixels, 16 colors
            8bpp : 1 byte, 1 pixel, 256 colors
            16bpp : 2 bytes, 1 pixel
            24bpp : 3 bytes, 1 pixel
            32bpp : 4 bytes, 1 pixel

            So, bpp/8 = color chunk size.

View on GitHub (pinned to a4d0a67c21)