wmjordan/PDFPatcher · error · NotSupportedException

不支持的像素格式: colorants={colorants}, spots={spots}, alpha={hasAl

Error message

不支持的像素格式: colorants={colorants}, spots={spots}, alpha={hasAlpha}

What it means

Thrown as NotSupportedException by the parameterless ToBitmap(this Pixmap) overload when the pixmap's channel layout does not match one of the four supported conversions: 8bpp grayscale (1 colorant / 1 colorant+alpha), 24bpp RGB (3 colorants, no alpha), 32bpp ARGB (3 colorants + alpha), or CMYK converted to RGB (4 colorants, no alpha). Any spot-color channels (spots>0), CMYK-with-alpha, or an unsupported colorant count falls through to this throw.

Source

Thrown at App/Processor/Mupdf/MuPDFExtensions.cs:286

		if (colorants == 3 && hasAlpha && spots == 0) {
			var bmp = new Bitmap(w, h, PixelFormat.Format32bppArgb);
			var data = bmp.LockBits(true);
			Copy32bppBgraUnpremultiply(pix, w, h, data);
			bmp.UnlockBits(data);
			return bmp;
		}

		if (colorants == 4 && !hasAlpha && spots == 0) {
			var bmp = new Bitmap(w, h, PixelFormat.Format24bppRgb);
			var data = bmp.LockBits(true);
			using (var rgbPix = pix.ConvertColorspace(ColorspaceKind.RGB, null)) {
				Copy24bppImage(rgbPix, w, h, false, data);
			}
			bmp.UnlockBits(data);
			return bmp;
		}

		throw new NotSupportedException(
			$"不支持的像素格式: colorants={colorants}, spots={spots}, alpha={hasAlpha}");
	}

	/// <summary>
	/// 将 Pixmap 的数据转换为 <see cref="Bitmap"/>。
	/// </summary>
	public static unsafe Bitmap ToBitmap(this Pixmap pix, ImageRendererOptions options) {
		int width = pix.Width;
		int height = pix.Height;
		bool grayscale = options.ColorSpace == (ColorSpace)ColorspaceKind.Gray;
		bool invert = options.InvertColor;
		var bmp = new Bitmap(width, height, grayscale ? PixelFormat.Format8bppIndexed : PixelFormat.Format24bppRgb);
		var imageData = bmp.LockBits(true);
		try {
			if (grayscale) {
				bmp.CreateStandardGrayscalePalette();
				Copy8bppImage(pix, width, height, invert, imageData);
			}

View on GitHub (pinned to 4782bbd9ad)

Solutions

1. Flatten the pixmap to DeviceRGB before conversion: using var rgb = pix.ConvertColorspace(ColorspaceKind.RGB, null); then call ToBitmap-equivalent copy on rgb.
2. Prefer the ToBitmap(this Pixmap pix, ImageRendererOptions options) overload (line 293) or RenderBitmapPage, which allocate a fixed RGB/Gray target and copy with Copy24bppImage/Copy8bppImage, bypassing this guard entirely.
3. Strip spot channels by converting through an intermediate RGB pixmap so spots/alpha are resolved by MuPDF.
4. Inspect pix.Colorants, pix.Spots, pix.Alpha before calling and skip/log unsupported layouts instead of letting it throw.

Example fix

// before (throws for spot/CMYK+alpha layouts)
var bmp = pix.ToBitmap();

// after (force RGB, no guard hit)
using var rgb = pix.ConvertColorspace(ColorspaceKind.RGB, null);
var bmp = new Bitmap(rgb.Width, rgb.Height, PixelFormat.Format24bppRgb);
var data = bmp.LockBits(true);
Copy24bppImage(rgb, rgb.Width, rgb.Height, false, data); // or use rgb.ToBitmap(options)

static bool IsSupportedPixmapLayout(Pixmap pix) {
    int c = pix.Colorants, s = pix.Spots;
    bool a = pix.Alpha == 1;
    if (s != 0) return false;
    if (c == 1) return true;                 // grayscale +/- alpha
    if (c == 3) return true;                 // RGB or RGBA
    if (c == 4 && !a) return true;           // CMYK (converted to RGB)
    return false;
}

static bool CanConvertToBitmap(Pixmap pix) =>
    pix.Spots == 0 && (pix.Colorants == 1 || pix.Colorants == 3 || (pix.Colorants == 4 && pix.Alpha == 0));

try {
    return pix.ToBitmap();
}
catch (NotSupportedException) {
    using var rgb = pix.ConvertColorspace(ColorspaceKind.RGB, null);
    return rgb.ToBitmap(); // retry on flattened RGB

When it happens

Trigger: Calling ToBitmap() on a Pixmap with spots > 0 (separation/space colorspaces), or colorants==4 && hasAlpha (CMYK+transparency), or colorants not in {1,3,4} (e.g. Lab/DeviceN with an unusual channel count), or colorants==0 && !hasAlpha. This is the parameterless ToBitmap(Pixmap) at line 237, NOT the RenderBitmapPage path which uses ToBitmap(pix, options) that forces RGB/Gray and never reaches this throw.

Common situations: Extracting embedded images that use spot/separation colorspaces (Pantone etc.); CMYK images that carry a soft mask or SMask alpha channel; DeviceN or ICCBased colorspaces whose pixmap exposes extra channels; rendering a page whose colorspace was not flattened to RGB before extraction.

Related errors

• 无法渲染页面：{(page.PageNumber + 1).ToText()}
• 在简易书签第 {lineNum} 行的缩进格式不正确。 说明：下级书签最多只能比上级书签多一个缩进标记。
• 简易书签文件内容不足。
• 找不到文件：{sourceFile}

AI-assisted analysis of wmjordan/PDFPatcher@4782bbd9ad (2026-08-13). Data as JSON: /api/errors/c1f35bd0640684f5. Report an issue: GitHub.