Convert RGB array to image in C#

Question

I know the rgb value of every pixel, and how can I create the picture by these values in C#? I've seen some examples like this:

public Bitmap GetDataPicture(int w, int h, byte[] data)
  {

  Bitmap pic = new Bitmap(this.width, this.height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
  Color c;

  for (int i = 0; i < data.length; i++)
  {
    c = Color.FromArgb(data[i]);
    pic.SetPixel(i%w, i/w, c);
  }

  return pic;
  }

But it does not works. I have a two-dimensional array like this:

1 3 1 2 4 1 3 ...
2 3 4 2 4 1 3 ...
4 3 1 2 4 1 3 ...
...

Each number correspond to a rgb value, for example, 1 => {244,166,89} 2=>{54,68,125}.

you dont know how to create a byte array?? how do you create an array of anything... sometype[] myname = ... — BugFinder, Aug 17 '16 at 06:52
Possible duplicate of [How to create bitmap from byte array?](http://stackoverflow.com/questions/21555394/how-to-create-bitmap-from-byte-array) — slawekwin, Aug 17 '16 at 06:52
what was your exact requirement? you need to create a bitmap image with rgb of every pixel or create bytearrray from image — Uthistran Selvaraj, Aug 17 '16 at 06:58
you have rgb of every pixel... right? also you know the height and width for which the image to be created.. right? — Uthistran Selvaraj, Aug 17 '16 at 07:01
how you have your rgb values now? i mean in which format? array/list/something — Uthistran Selvaraj, Aug 17 '16 at 07:12
If i not mistaken, are you have picture with indexed colors? I.e. picture is a array of bytes, where each byte value correspond to some 3-byte RGB color? — Alexander Kiselev, Aug 17 '16 at 07:51
@hashtabe_0 I don't get it, really. The question makes it sound like you *have* a byte array and want to create the bitmap from it, the comments say that you *just donnt know how to convert it into a byte array*. So which one is it? Do you want to create the bitmap from an existing byte array or do you want to create the byte array from an existing bitmap? — Thorsten Dittmar, Aug 17 '16 at 09:29

Thorsten Dittmar · Accepted Answer · 2020-10-10T08:27:48.783

3

I'd try the following code, which uses an array of 256 Color entries for the palette (you have to create and fill this in advance):

public Bitmap GetDataPicture(int w, int h, byte[] data)
{
    Bitmap pic = new Bitmap(w, h, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

    for (int x = 0; x < w; x++)
    {
        for (int y = 0; y < h; y++)
        {
            int arrayIndex = y * w + x;
            Color c = Color.FromArgb(
               data[arrayIndex],
               data[arrayIndex + 1],
               data[arrayIndex + 2],
               data[arrayIndex + 3]
            );
            pic.SetPixel(x, y, c);
        }
    }

    return pic;
}

I tend to iterate over the pixels, not the array, as I find it easier to read the double loop than the single loop and the modulo/division operation.

edited Oct 10 '20 at 08:27

answered Aug 17 '16 at 09:26

Thorsten Dittmar

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how to declare the palette variable? – Inside Man Oct 10 '20 at 06:18
@InsideMan Actually this was a mistake in my code. The "palette" variable should have been the "data" variable, which is w * h * 4 bytes long and contains the ARGB values for each pixel. – Thorsten Dittmar Oct 10 '20 at 08:29

Alexander Kiselev · Answer 2 · 2016-08-17T08:23:18.147

Your solution very near to working code. Just you need the "palette" - i.e. set of 3-elements byte array, where each 3-bytes element contains {R, G, B} values.

    //palette is a 256x3 table
    public static Bitmap GetPictureFromData(int w, int h, byte[] data, byte[][] palette)
    {
      Bitmap pic = new Bitmap(w, h, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
      Color c;

      for (int i = 0; i < data.Length; i++)
      {
          byte[] color_bytes = palette[data[i]];
          c = Color.FromArgb(color_bytes[0], color_bytes[1], color_bytes[2]);
          pic.SetPixel(i % w, i / w, c);
      }

      return pic;
    }

This code works for me, but it very slow.

If you create in-memory "image" of BMP-file and then use Image.FromStream(MemoryStream("image")), it code will be more faster, but it more complex solution.

Convert RGB array to image in C#

2 Answers2

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