d2phap/ImageGlass · error · Exception

Failed WebPGetFeatures with error {result}

Error message

Failed WebPGetFeatures with error {result}

What it means

Thrown in WebPWrapper.Decode when LibWebp.WebPGetFeatures returns a status other than VP8_STATUS_OK. WebPGetFeatures parses the WebP bitstream header (dimensions, alpha, animation flags); a non-OK status means the input bytes are not a valid WebP, are truncated, or are a WebP container the decoder cannot read. This happens AFTER the ABI handshake (error 50) has passed, so the native library is fine — the data is the problem.

Source

Thrown at v9/Components/ImageGlass.WebP/WebPWrapper.cs:151

        Bitmap? bmp = null;
        BitmapData? bmpData = null;
        VP8StatusCode result;
        try
        {
            WebPDecoderConfig config = new WebPDecoderConfig();
            if (LibWebp.WebPInitDecoderConfig(ref config) == 0)
            {
                throw new Exception("WebPInitDecoderConfig failed. Wrong version?");
            }
            // Read the .webp input file information
            IntPtr ptrRawWebP = pinnedWebP.AddrOfPinnedObject();
            int height;
            int width;
            if (options.use_scaling == 0)
            {
                result = LibWebp.WebPGetFeatures(ptrRawWebP, rawWebP.Length, ref config.input);
                if (result != VP8StatusCode.VP8_STATUS_OK)
                    throw new Exception("Failed WebPGetFeatures with error " + result);

                //Test cropping values
                if (options.use_cropping == 1)
                {
                    if (options.crop_left + options.crop_width > config.input.Width || options.crop_top + options.crop_height > config.input.Height)
                        throw new Exception("Crop options exceeded WebP image dimensions");
                    width = options.crop_width;
                    height = options.crop_height;
                }
            }
            else
            {
                width = options.scaled_width;
                height = options.scaled_height;
            }

            config.options.bypass_filtering = options.bypass_filtering;
            config.options.no_fancy_upsampling = options.no_fancy_upsampling;

View on GitHub (pinned to 4a3c4fecef)

Solutions

1. Validate the input starts with the WebP RIFF signature ('RIFF'....'WEBP') before calling Decode; reject early with a clear error.
2. Re-fetch or re-encode the source WebP from a known-good origin to rule out truncation/corruption.
3. Update libwebp to a version that supports the WebP feature set in your inputs.
4. Catch the exception at the call site and treat the file as undecodable rather than crashing the batch.

Example fix

// before
var bmp = WebPWrapper.Decode(rawWebP, options);

// after: signature guard + status handling
if (rawWebP.Length < 12 ||
    System.Text.Encoding.ASCII.GetString(rawWebP, 0, 4) != "RIFF" ||
    System.Text.Encoding.ASCII.GetString(rawWebP, 8, 4) != "WEBP")
    throw new InvalidDataException("Not a valid WebP stream.");
var bmp = WebPWrapper.Decode(rawWebP, options);

// Reject non-WebP input before decoding.
static bool IsWebP(byte[] b) => b.Length >= 12 &&
    Encoding.ASCII.GetString(b, 0, 4) == "RIFF" &&
    Encoding.ASCII.GetString(b, 8, 4) == "WEBP";
if (!IsWebP(rawWebP)) throw new InvalidDataException("Not a WebP stream.");

static bool IsWebP(byte[] b) => b.Length >= 12 &&
    Encoding.ASCII.GetString(b, 0, 4) == "RIFF" &&
    Encoding.ASCII.GetString(b, 8, 4) == "WEBP";

try { bmp = WebPWrapper.Decode(rawWebP, options); }
catch (Exception ex) when (ex.Message.Contains("WebPGetFeatures"))
{ /* corrupt/truncated or non-WebP input */ }

When it happens

Trigger: Passing non-WebP bytes (wrong format, a JPEG/PNG mislabeled .webp); a truncated/corrupt WebP downloaded incompletely; a WebP with features this libwebp build doesn't support (e.g. extended container without the right build); a zero-length or near-empty buffer.

Common situations: Reading a .webp from an unreliable network/clipboard that got truncated; a file with a renamed extension; feeding a WebP that uses a newer feature than the bundled libwebp supports.

Related errors

• Failed WebPDecode with error {result}
• Crop options exceeded WebP image dimensions
• WebPInitDecoderConfig failed. Wrong version?
• Bitmap contains no data.
• The base64 content is invalid.

AI-assisted analysis of d2phap/ImageGlass@4a3c4fecef (2026-08-13). Data as JSON: /api/errors/d777566158cac05f. Report an issue: GitHub.