By using the XImage.Raster SDK, you can modify the image's bit in per pixel by assigning to the processor. The method QuantizeColor can be used to decrease the bit depth of an image with the specified dither method(DitherMethod enumeration) and color space(ColorSpace enumeration).
Sample Code (modify image bit depth):
RasterImage img = new RasterImage(@"F:\input.tif");
ImageProcess process = new ImageProcess(img);
//Decrease the bit depth, decrease the 24 bits per pixel image input.jpg to 8 bits per pixel.
process.QuantizeColor(8, DitherMethod.FloydSteinbergDitherMethod, ColorSpace.GRAY);
//If the image has multiple frames,>
//only decrease the second pages bit depth
process.QuantizeColor(8, DitherMethod.FloydSteinbergDitherMethod, ColorSpace.GRAY, 1);
img.Save(@"C:\output.tif">)
