''' <summary>
''' Compares two images and highlights the comparison result with red color.
''' </summary>
''' <param name="image1Filename">The filename of first image.</param>
''' <param name="image2Filename">The filename of second image.</param>
''' <param name="resultFilename">The filename of result image.</param>
Public Sub CompareImages(image1Filename As String, image2Filename As String, resultFilename As String)
    ' open the first image
    Using image1 As New Vintasoft.Imaging.VintasoftImage(image1Filename)
        ' open the second image
        Using image2 As New Vintasoft.Imaging.VintasoftImage(image2Filename)
            ' create the image comparison command
            Dim imageComparison As New Vintasoft.Imaging.ImageProcessing.ImageComparisonCommand(image2)

            ' get the grayscale result of comparing two images
            Using differences As Vintasoft.Imaging.VintasoftImage = imageComparison.Execute(image1)
                ' creates the colors for the differences palette with the red color as main color
                Dim colors As Integer() = CreateDifferencesPaletteColors(System.Drawing.Color.Red)
                differences.Palette.SetColors(colors)

                ' if pixel format of image1 is not Bgr24 or Bgr32 or Bgra32
                If image1.PixelFormat <> Vintasoft.Imaging.PixelFormat.Bgr24 AndAlso image1.PixelFormat <> Vintasoft.Imaging.PixelFormat.Bgr32 AndAlso image1.PixelFormat <> Vintasoft.Imaging.PixelFormat.Bgra32 Then
                    ' change pixel format of image1 to Bgr24
                    Dim changeFormat As New Vintasoft.Imaging.ImageProcessing.ChangePixelFormatCommand()
                    changeFormat.PixelFormat = Vintasoft.Imaging.PixelFormat.Bgr24
                    changeFormat.ExecuteInPlace(image1)
                End If

                ' if image1 and the comparison result image have different sizes
                If image1.Width <> differences.Width OrElse image1.Height <> differences.Height Then
                    ' crop image1 to the comparison result image size
                    Dim crop As New Vintasoft.Imaging.ImageProcessing.CropCommand()
                    crop.RegionOfInterest = New Vintasoft.Imaging.RegionOfInterest(0, 0, differences.Width, differences.Height)
                    crop.ExecuteInPlace(image1)
                End If

                ' draw the comparison result on the top of image1
                Dim differencesGraphics As System.Drawing.Graphics = Vintasoft.Imaging.VintasoftImageGdiExtensions.OpenGraphics(image1)
                Vintasoft.Imaging.VintasoftImageGdiExtensions.Draw(differences, differencesGraphics, New System.Drawing.Rectangle(0, 0, differences.Width, differences.Height))
                Vintasoft.Imaging.VintasoftImageGdiExtensions.CloseGraphics(image1)

                ' save the processed image to the new file
                image1.Save(resultFilename)
            End Using
        End Using
    End Using
End Sub

''' <summary>
''' Creates the colors for the differences palette.
''' </summary>
''' <param name="color">Main color for the differences palette.</param>
''' <returns>The colors for the differences palette.</returns>
Private Function CreateDifferencesPaletteColors(color As System.Drawing.Color) As Integer()
    Dim colors As Integer() = New Integer(255) {}
    For i As Integer = 0 To 255
        Dim alpha As Byte = CByte(i)
        colors(i) = (alpha << 24) Or (color.R << 16) Or (color.G << 8) Or color.B
    Next
    Return colors
End Function

/// <summary>
/// Compares two images and highlights the comparison result with red color.
/// </summary>
/// <param name="image1Filename">The filename of first image.</param>
/// <param name="image2Filename">The filename of second image.</param>
/// <param name="resultFilename">The filename of result image.</param>
public void CompareImages(string image1Filename, string image2Filename, string resultFilename)
{
    // open the first image
    using (Vintasoft.Imaging.VintasoftImage image1 = new Vintasoft.Imaging.VintasoftImage(image1Filename))
    {
        // open the second image
        using (Vintasoft.Imaging.VintasoftImage image2 = new Vintasoft.Imaging.VintasoftImage(image2Filename))
        {
            // create the image comparison command
            Vintasoft.Imaging.ImageProcessing.ImageComparisonCommand imageComparison =
                new Vintasoft.Imaging.ImageProcessing.ImageComparisonCommand(image2);

            // get the grayscale result of comparing two images
            using (Vintasoft.Imaging.VintasoftImage differences = imageComparison.Execute(image1))
            {
                // creates the colors for the differences palette with the red color as main color
                int[] colors = CreateDifferencesPaletteColors(System.Drawing.Color.Red);
                differences.Palette.SetColors(colors);

                // if pixel format of image1 is not Bgr24 or Bgr32 or Bgra32
                if (image1.PixelFormat != Vintasoft.Imaging.PixelFormat.Bgr24 && 
                    image1.PixelFormat != Vintasoft.Imaging.PixelFormat.Bgr32 && 
                    image1.PixelFormat != Vintasoft.Imaging.PixelFormat.Bgra32)
                {
                    // change pixel format of image1 to Bgr24
                    Vintasoft.Imaging.ImageProcessing.ChangePixelFormatCommand changeFormat = 
                        new Vintasoft.Imaging.ImageProcessing.ChangePixelFormatCommand();
                    changeFormat.PixelFormat = Vintasoft.Imaging.PixelFormat.Bgr24;
                    changeFormat.ExecuteInPlace(image1);
                }

                // if image1 and the comparison result image have different sizes
                if (image1.Width != differences.Width || image1.Height != differences.Height)
                {
                    // crop image1 to the comparison result image size
                    Vintasoft.Imaging.ImageProcessing.CropCommand crop = 
                        new Vintasoft.Imaging.ImageProcessing.CropCommand();
                    crop.RegionOfInterest = 
                        new Vintasoft.Imaging.RegionOfInterest(0, 0, differences.Width, differences.Height);
                    crop.ExecuteInPlace(image1);
                }

                // draw the comparison result on the top of image1
                System.Drawing.Graphics differencesGraphics = Vintasoft.Imaging.VintasoftImageGdiExtensions.OpenGraphics(image1);
                Vintasoft.Imaging.VintasoftImageGdiExtensions.Draw(differences,
                    differencesGraphics, 
                    new System.Drawing.Rectangle(0, 0, differences.Width, differences.Height));
                Vintasoft.Imaging.VintasoftImageGdiExtensions.CloseGraphics(image1);

                // save the processed image to the new file
                image1.Save(resultFilename);
            }
        }
    }
}

/// <summary>
/// Creates the colors for the differences palette.
/// </summary>
/// <param name="color">Main color for the differences palette.</param>
/// <returns>The colors for the differences palette.</returns>
private int[] CreateDifferencesPaletteColors(System.Drawing.Color color)
{
    int[] colors = new int[256];
    for (int i = 0; i < 256; i++)
    {
        byte alpha = (byte)i;
        colors[i] = (alpha << 24) | (color.R << 16) | (color.G << 8) | color.B;
    }
    return colors;
}