将.jpg图像的像素值读取到字节数组中

Question

I'm trying to write a program in c# to send a frame via ethernet.

Currently I have .jpg test images in 1920x1080 resolution and very different sizes in bytes.

I am trying to convert a .jpg image to a byte array, I looked for similar answers but when I tried them I got byte arrays including 437, 1030, 1013 bytes for each image. Considering that the images are in HD resolution, this does not make sense. How can I convert an image file to form a 1920*1080*3 (RGB) byte array? Please keep in mind that I am trying to develop a real time application that should be able to send frames at a high rate so this code cannot be slow.

Thanks in advance. Tunc

Answer 1

to read Image bytes to byte array:

                Image image = ...;
                MemoryStream ms = new MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

                if (ms.Length == 0)
                {
                    ms.Close();
                    throw new Exception("Bad Image File");
                }

                ms.Position = 0;
                byte[] baImageBytes = new byte[ms.Length];
                ms.Read(baImageBytes , 0, (int)ms.Length);
                ms.Close();

to create image from byte array:

byte[] baImageBytes =...
Image myImage = Image.FromStream(new MemoryStream(baImageBytes ));

Answer 2

JPG is a compressed format, that's why its size (and size of the corresponding Byte array) will be usually far less than 1920*1080*3. In order to get Byte array from JPG you can use streams:

  Image myImage; 
  ...
  byte[] result;

  using (MemoryStream ms = new MemoryStream()) {
    myImage.Save(ms, ImageFormat.Jpeg); 

    result = ms.ToArray();
  }

If all you want are pixels in a form of Byte array you have to convert your JPG into BMP (or other raw, uncompressed format)

  Bitmap myImage;
  ... 
  byte[] rgbValues = null;

  BitmapData data = myImage.LockBits(new Rectangle(0, 0, myImage.Width, myImage.Height), ImageLockMode.ReadOnly, value.PixelFormat);

  try {
    IntPtr ptr = data.Scan0;
    int bytes = Math.Abs(data.Stride) * myImage.Height;
    rgbValues = new byte[bytes];
    Marshal.Copy(ptr, rgbValues, 0, bytes);
  }
  finally {
    myImage.UnlockBits(data);
  }
}