dotnet/wpf · error · ArgumentException

SR.Image_BadPixelFormat

Error message

SR.Image_BadPixelFormat

What it means

The PixelFormat(string) constructor parses the given pixel format name against a fixed list of known WPF/WIC formats (e.g. Bgr32, Gray16, Cmyk32). If the string does not case-insensitively match any known format, it throws ArgumentException with Image_BadPixelFormat naming the offending string. WPF supports only its enumerated PixelFormat set; arbitrary format names are rejected at construction time.

Solutions

1. Use the exact supported format name; compare against PixelFormats.* properties to pick a valid one
2. Map foreign format names to the nearest WPF equivalent before constructing (e.g. "RGBA8888" -> "Pbgra32" or "Bgra32")
3. Validate the string against PixelFormats properties before calling the constructor
4. If the format is genuinely unsupported, convert the bitmap to a supported format first (e.g. FormatConvertedBitmap)

Example fix

// before
var pf = new PixelFormat("RGBA32"); // throws
// after
var pf = new PixelFormat("Pbgra32"); // or use PixelFormats.Pbgra32

bool IsValidPixelFormatName(string s) =>
  new[]{"Default","Extended","Indexed1","Indexed2","Indexed4","Indexed8","BlackWhite","Gray2","Gray4","Gray8","Gray16","Gray32Float","Bgr555","Bgr32","Bgra32","Pbgra32","Rgb48","Rgba64","Prgba64","Rgb128Float","Rgba128Float","Prgba128Float","Cmyk32"}
  .Any(n => n.Equals(s, StringComparison.OrdinalIgnoreCase));

bool IsPixelFormatString(object v) => v is string s && IsValidPixelFormatName(s);

try { var pf = new PixelFormat(name); }
catch (ArgumentException ex) { log(ex); pf = PixelFormats.Default; }

When it happens

Trigger: new PixelFormat("someString") where the string is not one of the supported names: Default, Extended, Indexed1/2/4/8, Bgr555, Bgr32, Bgra32, Pbgra32, Gray2/4/8/16, Gray32Float, Rgb48, Rgba64, Prgba64, Rgb128Float, Rgba128Float, Prgba128Float, Cmyk32, BlackWhite.

Common situations: Typo in XAML or serialized pixel format strings (e.g. "BGRA32" is fine case-insensitively, but "RGBA32" or "BGR24" are not); round-tripping pixel format names from other imaging libraries (GDI+, Skia, OpenCV) whose naming differs; machine-generated config with invalid format.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• SR.Collection_BadRank
• SR.Collection_BadRank
• SR.Format(SR.General_Expected_Type, nameof(PixelFormat))
• SR.Image_AlphaThresholdOutOfRange
• SR.Image_InvalidArrayForPixel

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/245b81afa7a9ca7e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/PixelFormat.cs:223

                _ when pixelFormatString.Equals("Gray8", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Gray8,
                _ when pixelFormatString.Equals("Bgr555", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Bgr555,
                _ when pixelFormatString.Equals("Bgr565", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Bgr565,
                _ when pixelFormatString.Equals("Bgr24", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Bgr24,
                _ when pixelFormatString.Equals("Rgb24", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Rgb24,
                _ when pixelFormatString.Equals("Bgr101010", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Bgr101010,
                _ when pixelFormatString.Equals("Bgr32", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Bgr32,
                _ when pixelFormatString.Equals("Bgra32", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Bgra32,
                _ when pixelFormatString.Equals("Pbgra32", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Pbgra32,
                _ when pixelFormatString.Equals("Rgb48", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Rgb48,
                _ when pixelFormatString.Equals("Rgba64", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Rgba64,
                _ when pixelFormatString.Equals("Prgba64", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Prgba64,
                _ when pixelFormatString.Equals("Gray16", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Gray16,
                _ when pixelFormatString.Equals("Gray32Float", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Gray32Float,
                _ when pixelFormatString.Equals("Rgb128Float", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Rgb128Float,
                _ when pixelFormatString.Equals("Rgba128Float", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Rgba128Float,
                _ when pixelFormatString.Equals("Prgba128Float", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Prgba128Float,
                _ when pixelFormatString.Equals("Cmyk32", StringComparison.OrdinalIgnoreCase) => PixelFormatEnum.Cmyk32,
                _ => throw new ArgumentException(SR.Format(SR.Image_BadPixelFormat, pixelFormatString), nameof(pixelFormatString)),
            };

            _flags = GetPixelFormatFlagsFromEnum(_format);
            _bitsPerPixel = GetBitsPerPixelFromEnum(_format);
            _guidFormat = GetGuidFromFormat(_format);
        }

        private static Guid GetGuidFromFormat(PixelFormatEnum format) => format switch
        {
            PixelFormatEnum.Default => WICPixelFormatGUIDs.WICPixelFormatDontCare,
            PixelFormatEnum.Indexed1 => WICPixelFormatGUIDs.WICPixelFormat1bppIndexed,
            PixelFormatEnum.Indexed2 => WICPixelFormatGUIDs.WICPixelFormat2bppIndexed,
            PixelFormatEnum.Indexed4 => WICPixelFormatGUIDs.WICPixelFormat4bppIndexed,
            PixelFormatEnum.Indexed8 => WICPixelFormatGUIDs.WICPixelFormat8bppIndexed,
            PixelFormatEnum.BlackWhite => WICPixelFormatGUIDs.WICPixelFormatBlackWhite,
            PixelFormatEnum.Gray2 => WICPixelFormatGUIDs.WICPixelFormat2bppGray,
            PixelFormatEnum.Gray4 => WICPixelFormatGUIDs.WICPixelFormat4bppGray,
            PixelFormatEnum.Gray8 => WICPixelFormatGUIDs.WICPixelFormat8bppGray,

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