Accord.Imaging.Formats.PNMCodec.ReadP6Image C# (CSharp) Method

        private static unsafe Bitmap ReadP6Image(Stream stream, int width, int height, int maxValue)
        {
            double scalingFactor = (double)255 / maxValue;

            // create new bitmap and lock it
            Bitmap image = new Bitmap(width, height, PixelFormat.Format24bppRgb);
            BitmapData imageData = image.LockBits(new Rectangle(0, 0, width, height),
                ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

            int stride = imageData.Stride;
            byte* ptr = (byte*)imageData.Scan0.ToPointer();

            // prepare a buffer for one line
            int lineSize = width * 3;
            byte[] line = new byte[lineSize];

            int totalBytesRead = 0, bytesRead = 0;

            // load all rows
            for (int y = 0; y < height; y++)
            {
                totalBytesRead = 0;
                bytesRead = 0;

                // load next line
                while (totalBytesRead != lineSize)
                {
                    bytesRead = stream.Read(line, totalBytesRead, lineSize - totalBytesRead);

                    if (bytesRead == 0)
                    {
                        // if we've reached the end before complete image is loaded, then there should
                        // be something wrong
                        throw new InvalidOperationException("Execution should not reach here.");
                    }

                    totalBytesRead += bytesRead;
                }

                // fill next image row
                byte* row = ptr + stride * y;

                for (int x = 0, i = 0; x < width; x++, i += 3, row += 3)
                {
                    row[2] = (byte)(scalingFactor * line[i]);       // red
                    row[1] = (byte)(scalingFactor * line[i + 1]);   // green
                    row[0] = (byte)(scalingFactor * line[i + 2]);   // blue
                }
            }

            // unlock image and return it
            image.UnlockBits(imageData);
            return image;
        }