I'm trying to save a JPEG as a grayscale image.
I found the code below that will make it grayscale by blending the channels, but it still has all three RGB channels. I only need one 8 bit channel.
public static Bitmap MakeGrayscale(Bitmap original)
{
//create a blank bitmap the same size as original
Bitmap newBitmap = new Bitmap(original.Width, original.Height);
//get a graphics object from the new image
Graphics g = Graphics.FromImage(newBitmap);
//create the grayscale ColorMatrix
ColorMatrix colorMatrix = new ColorMatrix(
new float[][]
{
new float[] {.3f, .3f, .3f, 0, 0},
new float[] {.59f, .59f, .59f, 0, 0},
new float[] {.11f, .11f, .11f, 0, 0},
new float[] {0, 0, 0, 1, 0},
new float[] {0, 0, 0, 0, 1}
});
//create some image attributes
ImageAttributes attributes = new ImageAttributes();
//set the color matrix attribute
attributes.SetColorMatrix(colorMatrix);
//draw the original image on the new image
//using the grayscale color matrix
g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height),
0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes);
//dispose the Graphics object
g.Dispose();
return newBitmap;
}
Is there any way in C# to actually set the color mode of JPEG?
I've tried the following, but it still outputs a 24 bit RGB image.
ImageCodecInfo codec = GetEncoderInfo("image/jpeg");
System.Drawing.Imaging.Encoder enc = System.Drawing.Imaging.Encoder.ColorDepth;
EncoderParameters encParams = new EncoderParameters(1);
encParams.Param[0] = new EncoderParameter(enc, 8L);
source_bitmap.Save(outputFile, codec, encParams);