protected override void DoWork(IProgress<string> progress, CancellationToken cancellationToken)
        {
            cancellationToken.Register(SwitchToCancelledState);

            var processorCount = Environment.ProcessorCount;

            using (var bmp = new Bitmap(fileName))
            {
                // Lock the bitmap's bits.
                var rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
                var bmpData =
                    bmp.LockBits(rect, ImageLockMode.ReadWrite,
                        bmp.PixelFormat);

                // Get the address of the first line.
                var ptr = bmpData.Scan0;

                // Declare an array to hold the bytes of the bitmap.
                var bytes = Math.Abs(bmpData.Stride) * bmp.Height;
                var rgbValues = new byte[bytes];

                // Copy the RGB values into the array.
                System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);

                var partSize = rgbValues.Length / processorCount;
                var oneQuarter = rgbValues.Length / 100 * 25;
                var i = -25;
                var counter = 0;


                for (var j = 0; j <= rgbValues.Length - partSize; j += partSize)
                {
                    var start = j;
                    var end = j + partSize - 1;

                    Task.Run(() =>
                    {
                        for (var k = start; k <= end; k++)
                        {
                            rgbValues[k] = (byte) (rgbValues[k] + brightnessChange);

                            Interlocked.Increment(ref counter);
                            if (counter % oneQuarter != 0) return;
                            i += 25;
                            progress.Report($"Brightness job (ID {Id}) - {i}%");

                        }
                    }, cancellationToken);

                }

                Task.WaitAll();

                // Copy the RGB values back to the bitmap
                System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);

                // Unlock the bits.
                bmp.UnlockBits(bmpData);

                // Save image
                bmp.Save(Paths.GetOutputImageFullName(Id, "brightness" + brightnessChange), ImageFormat.Jpeg);
            }

            SwitchToFinishedState($"Changed brightness by {brightnessChange} point(s)");
        }
    }