ImageColorMode

public enum ImageColorMode

Document doc = new Document();
DocumentBuilder builder = new DocumentBuilder(doc);

builder.ParagraphFormat.Style = doc.Styles["Heading 1"];
builder.Writeln("Hello world!");
builder.InsertImage(ImageDir + "Logo.jpg");

// When we save the document as an image, we can pass a SaveOptions object to
// select a color mode for the image that the saving operation will generate.
// If we set the "ImageColorMode" property to "ImageColorMode.BlackAndWhite",
// the saving operation will apply grayscale color reduction while rendering the document.
// If we set the "ImageColorMode" property to "ImageColorMode.Grayscale", 
// the saving operation will render the document into a monochrome image.
// If we set the "ImageColorMode" property to "None", the saving operation will apply the default method
// and preserve all the document's colors in the output image.
ImageSaveOptions imageSaveOptions = new ImageSaveOptions(SaveFormat.Png);
imageSaveOptions.ImageColorMode = imageColorMode;

doc.Save(ArtifactsDir + "ImageSaveOptions.ColorMode.png", imageSaveOptions);