Show an array of bytes as an image on a form-CodePudding

I wrote some code to show an array of bytes as an image. There is an array of bytes in which every element represents a value of 8-bit gray scale image. Zero equals the most black and 255 does the most white pixel. My goal is to convert this w*w-pixel gray-scale image to some thing accepted by pictureBox1.Image. This is my code:

namespace ShowRawImage
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();         
        }

        private void button1_Click(object sender, EventArgs e)
        {
            int i = 0, j = 0, w = 256;
            byte[] rawIm = new byte[256 * 256];
            for(i = 0; i < w;   i)
            {
                for (j = 0; j < w;   j)
                {
                    rawIm[i * w   j] = (byte)j; // BitConverter.GetBytes(j);
                }
            }

            MemoryStream mStream = new MemoryStream();
            mStream.Write(rawIm, 0, Convert.ToInt32(rawIm.Length));
            Bitmap bm = new Bitmap(mStream, false);// the error occurs here
            mStream.Dispose();
            pictureBox1.Image = bm;

        }
    }
}

However I get this error: Parameter is not valid.

But if you don't want to use unsafe code, or you want to set pixels by colors, you can use this library (disclaimer: written by me) that supports efficient manipulation regardless of the actual PixelFormat. Using that library the last block can be rewritten like this:

using (IWritableBitmapData bitmapData = bmp.GetWritableBitmapData())
{
    IWritableBitmapDataRow row = bitmapData.FirstRow;
    do
    {
        for (int x = 0; x < bitmapData.Width; x  )
            row[x] = Color32.FromGray((byte)x); // this works for any pixel format
            // row.SetColorIndex(x, x); // for the grayscale 8bpp bitmap created above
    } while (row.MoveNextRow());
}

Or like this, using Parallel.For (this works only because in your example all rows are the same so the image is a horizontal gradient):

using (IWritableBitmapData bitmapData = bmp.GetWritableBitmapData())
{
    Parallel.For(0, bitmapData.Height, y =>
    {
        var row = bitmapData[y];
        for (int x = 0; x < bitmapData.Width; x  )
            row[x] = Color32.FromGray((byte)x); // this works for any pixel format
            // row.SetColorIndex(x, x); // for the grayscale 8bpp bitmap created above
    });
}

CodePudding user response：

As said in the comments - bitmap is not just an array. So to reach your goal you can create bitmap of needed size and set pixels with Bitmap.SetPixel:

Bitmap bm = new Bitmap(w, w);
for(var i = 0; i < w;   i)
{
    for (var j = 0; j < w;   j)
    {
        bm.SetPixel(i,j, Color.FromArgb(j, j, j));
    }
}