c# How can I show histogram data on the image

Question

I have an image and using aforgenet histogram, I am able to get vertical and horizontal histogram value in an array form. I can create a graph based on it but i wanted to display the value on the same image with different color based on vertical and horizontal. Nutshell i wanted to plot the data on the image based on its histogram value.

// get image statistics
AForge.Imaging.ImageStatistics statistics =
new AForge.Imaging.ImageStatistics( image );
// get the red histogram
AForge.Math.Histogram histogram = statistics.Red;
// get the values
double mean = histogram.Mean;     // mean red value
double stddev = histogram.StdDev; // standard deviation of red values
int    median = histogram.Median; // median red value
int    min = histogram.Min;       // min red value
int    max = histogram.Max;       // max value
// get 90% range around the median
AForge.IntRange range = histogram.GetRange( 0.9 );

Answer 1

AForge.net has a sample application called IPLab .

It has the following source code to show Histogram in a Form:

public class HistogramWindow : Content
{
    #region Windows form designer generated code
    //.... ... ...
    #endregion        

    #region gather stats
    //... ... ...
    #endregion

    private static Color[] colors = new Color[] 
    {
        Color.FromArgb(192, 0, 0),
        Color.FromArgb(0, 192, 0),
        Color.FromArgb(0, 0, 192),
        Color.FromArgb(128, 128, 128),
    };

    private int currentImageHash = 0;
    private ImageStatistics stat;
    private AForge.Controls.Histogram histogram;
    private AForge.Math.Histogram activeHistogram = null;

    public HistogramWindow()
    {
        InitializeComponent();
    }

    // selection changed in channels combo
    private void channelCombo_SelectedIndexChanged( object sender, System.EventArgs e )
    {
        if ( stat != null )
        {
            SwitchChannel( ( stat.IsGrayscale ) ? 3 : channelCombo.SelectedIndex );
        }
    }

    // Switch channel
    public void SwitchChannel( int channel )
    {
        if ( ( channel >= 0 ) && ( channel <= 2 ) )
        {
            if ( !stat.IsGrayscale )
            {
                histogram.Color = colors[channel];
                activeHistogram = ( channel == 0 ) ? stat.Red : ( channel == 1 ) ? stat.Green : stat.Blue;
            }
        }
        else if ( channel == 3 )
        {
            if ( stat.IsGrayscale )
            {
                histogram.Color = colors[3];
                activeHistogram = stat.Gray;
            }
        }

        if ( activeHistogram != null )
        {
            histogram.Values = activeHistogram.Values;

            meanLabel.Text = activeHistogram.Mean.ToString( "F2" );
            stdDevLabel.Text = activeHistogram.StdDev.ToString( "F2" );
            medianLabel.Text = activeHistogram.Median.ToString( );
            minLabel.Text = activeHistogram.Min.ToString( );
            maxLabel.Text = activeHistogram.Max.ToString( );
        }
    }

    // Cursor position changed over the hostogram
    private void histogram_PositionChanged( object sender, AForge.Controls.HistogramEventArgs e )
    {
        int pos = e.Position;

        if ( pos != -1 )
        {
            levelLabel.Text = pos.ToString( );
            countLabel.Text = activeHistogram.Values[pos].ToString( );
            percentileLabel.Text = ( (float) activeHistogram.Values[pos] * 100 / stat.PixelsCount ).ToString( "F2" );
        }
        else
        {
            levelLabel.Text = "";
            countLabel.Text = "";
            percentileLabel.Text = "";
        }
    }

    // Selection changed in the hostogram
    private void histogram_SelectionChanged( object sender, AForge.Controls.HistogramEventArgs e )
    {
        int min = e.Min;
        int max = e.Max;
        int count = 0;

        levelLabel.Text = min.ToString( ) + "..." + max.ToString( );

        // count pixels
        for ( int i = min; i <= max; i++ )
        {
            count += activeHistogram.Values[i];
        }
        countLabel.Text = count.ToString( );
        percentileLabel.Text = ( (float) count * 100 / stat.PixelsCount ).ToString( "F2" );
    }

    // On "Log" check - switch mode
    private void logCheck_CheckedChanged( object sender, System.EventArgs e )
    {
        histogram.IsLogarithmicView = logCheck.Checked;
    }
}

You can examine and reuse the source code. It is pretty straight forward.