// AForge Image Processing Library

// AForge.NET framework

//

// Copyright © Andrew Kirillov, 2005-2007

// andrew.kirillov@gmail.com

//



namespace AForge.Imaging.Filters

{

    using System;

    using System.Drawing;

    using System.Drawing.Imaging;



    /// <summary>

    /// Threshold binarization.

    /// </summary>

    /// 

    /// <remarks><para>The filter does image binarization using specified threshold value. All pixels

    /// with intensities equal or higher than threshold value are converted to white pixels. All other

    /// pixels with intensities below threshold value are converted to black pixels.</para>

    /// <para>Sample usage:</para>

    /// <code>

    /// // create filter

    /// Threshold filter = new Threshold( 100 );

    /// // apply the filter

    /// filter.ApplyInPlace( image );

    /// </code>

    /// <para><b>Initial image:</b></para>

    /// <img src="grayscale.jpg" width="480" height="361" />

    /// <para><b>Result image:</b></para>

    /// <img src="threshold.jpg" width="480" height="361" />

    /// </remarks>

    /// 

    public class Threshold : FilterGrayToGrayPartial

    {

        /// <summary>

        /// Threshold value.

        /// </summary>

        protected byte threshold = 128;



        /// <summary>

        /// Threshold value.

        /// </summary>

        /// 

        /// <remarks>Default value is 128.</remarks>

        /// 

        public byte ThresholdValue

        {

            get { return threshold; }

            set { threshold = value; }

        }



        /// <summary>

        /// Initializes a new instance of the <see cref="Threshold"/> class.

        /// </summary>

        /// 

        public Threshold( ) { }



        /// <summary>

        /// Initializes a new instance of the <see cref="Threshold"/> class.

        /// </summary>

        /// 

        /// <param name="threshold">Threshold value.</param>

        /// 

        public Threshold( byte threshold )

        {

            this.threshold = threshold;

        }



        /// <summary>

        /// Process the filter on the specified image.

        /// </summary>

        /// 

        /// <param name="imageData">Image data.</param>

        /// <param name="rect">Image rectangle for processing by the filter.</param>

        /// 

        protected override unsafe void ProcessFilter( BitmapData imageData, Rectangle rect )

        {

            int startX  = rect.Left;

            int startY  = rect.Top;

            int stopX   = startX + rect.Width;

            int stopY   = startY + rect.Height;

            int offset  = imageData.Stride - rect.Width;



            // do the job

            byte* ptr = (byte*) imageData.Scan0.ToPointer( );



            // allign pointer to the first pixel to process

            ptr += ( startY * imageData.Stride + startX );



            // for each line	

            for ( int y = startY; y < stopY; y++ )

            {

                // for each pixel

                for ( int x = startX; x < stopX; x++, ptr++ )

                {

                    *ptr = (byte) ( ( *ptr >= threshold ) ? 255 : 0 );

                }

                ptr += offset;

            }

        }

    }

}