Converting to real 8bpp Jpeg

Question

I already searched and tried all the suggestions given it at SO, AForge, FreeImage and couple more websites, but I\'m unable to transform an image into a real 8bpp one. I always

Answer 1

UPDATE: The Image.Save() method does not support 8 bit per pixel for JPEG format. You may want to use the FreeImage library instead, as mentioned in the comments below.

---

If you want to reduce color depth to 8 bits per pixel, typically that is the same as converting from 24-bit color to grayscale, where each color channel has 8 bits per pixel to begin with. (In other words, reducing 3 channels of color information to 1.)

The default encoder when using Image.Save() and specifying ImageFormat.Jpeg is 24 bpp, so you'll need to specify an encoder and supply some parameters:

ImageCodecInfo[] availableCodecs = ImageCodecInfo.GetImageEncoders();
ImageCodecInfo jpgCodec = availableCodecs.FirstOrDefault(codec => codec.MimeType == "image/jpeg");
if (jpgCodec == null)
    throw new NotSupportedException("Encoder for JPEG not found.");

EncoderParameters encoderParams = new EncoderParameters(1);
encoderParams.Param[0] = new EncoderParameter(Encoder.ColorDepth, 8L);

myImage.Save("image_JPEG.jpg", jpgCodec, encoderParams);

This is a modified example from a longer explanation I found at aspnet-answers.com.