如何使用多个线程处理分区中的图像?

我正在尝试快速处理大型图像(约2000x2000)。我正在使用轨迹栏更改图像的整体亮度。问题是轨迹栏(大家都知道)可以很快移动。这是确定的,因为我不需要处理的图像 每一个 轨迹栏的勾号,但它确实需要合理的响应。想象一下图像编辑器中的亮度轨迹栏。

我尝试过在另一个线程中进行所有处理,这是可行的,但仍然太慢(即使在位图上使用锁位)。我不能使用ColorMatrix,因为它允许组件溢出,我需要在255处剪裁值。因此,我认为通过使用ThreadPool并将图像分割为多个部分,可以获得良好的性能。

这是我目前掌握的代码。我知道这远非好事,但我只是想解决它,并在这一点上尝试了许多不同的事情。基本概念是使用基础图像作为源,对每个像素执行一些操作,然后将处理后的像素绘制到显示位图中。任何帮助都会很棒。

    public Form1( )
    {
        InitializeComponent( );
        testPBox1.Image = Properties.Resources.test;
        trackBar1.Value = 100;
        trackBar1.ValueChanged += trackBar1_ValueChanged;        
    }     

    void trackBar1_ValueChanged( object sender, EventArgs e )
    {
        testPBox1.IntensityScale = (float) trackBar1.Value / 100;
    }

class TestPBox : Control
{
    private const int MIN_SAT_WARNING = 240;        
    private Bitmap m_srcBitmap;
    private Bitmap m_dispBitmap;
    private float m_scale;           

    public TestPBox( )
    {
        this.DoubleBuffered = true;                                              
        IntensityScale = 1.0f;
    }      

    public Bitmap Image
    {
        get
        {
            return m_dispBitmap;
        }
        set
        {
            if ( value != null )
            {
                m_srcBitmap = value;
                m_dispBitmap = (Bitmap) value.Clone( );
                Invalidate( );
            }
        }
    }

    [DefaultValue( 1.0f )]
    public float IntensityScale
    {
        get
        {
            return m_scale;
        }
        set
        {
            if ( value == 0.0 || m_scale == value )
            {                   
                return;
            }

            if ( !this.DesignMode )
            {
                m_scale = value;
                ProcessImage( );                    
            }
        }
    }   

    private void ProcessImage( )
    {
        if ( Image != null )
        {
            int sections = 10;
            int sectionHeight = (int) m_srcBitmap.Height / sections;
            for ( int i = 0; i < sections; ++i )
            {
                Rectangle next = new Rectangle( 0, i * sectionHeight, m_srcBitmap.Width, sectionHeight );
                ThreadPool.QueueUserWorkItem( new WaitCallback( delegate { ChangeIntensity( next ); } ) );
            }
        }
    }

    private unsafe void ChangeIntensity( Rectangle rect )
    {            
        BitmapData srcData = m_srcBitmap.LockBits( rect, ImageLockMode.ReadWrite, PixelFormat.Format32bppRgb );
        BitmapData dspData = m_dispBitmap.LockBits( rect, ImageLockMode.ReadWrite, PixelFormat.Format32bppRgb );            
        byte* pSrc = (byte*) srcData.Scan0;
        byte* pDsp = (byte*) dspData.Scan0;

        for ( int y = 0; y < rect.Height; ++y )
        {
            for ( int x = 0; x < rect.Width; ++x )
            {
                // we are dealing with a monochrome image, so r = g = b.
                // We only need to get one component value to use for all r, g, and b.
                byte b = (byte) CompMinMax( 0, 255, (int) ( pSrc[0] * m_scale ) );
                Color c = ( b > MIN_SAT_WARNING ) ? Color.FromArgb( b, Color.Red ) : Color.FromArgb( 255, b, b, b );                     

                // windows stores images internally in 
                // reverse byte order, i.e., Bgra, not Argb.
                pDsp[3] = (byte) c.A;
                pDsp[2] = (byte) c.R;
                pDsp[1] = (byte) c.G;
                pDsp[0] = (byte) c.B;

                pSrc += 4;
                pDsp += 4;                        
            }
        }

        m_srcBitmap.UnlockBits( srcData );
        m_dispBitmap.UnlockBits( dspData );
        this.Invalidate( );                      
    }

    private int CompMinMax( int min, int max, int value )
    {
        if ( value > max ) return max;
        if ( value < min ) return min;
        return value;
    }        

    protected override void OnPaint( PaintEventArgs e )
    {
        if ( Image != null )
        {               
            Graphics g = e.Graphics;
            Rectangle drawingRect = PaintUtils.CenterInRect( ClientRectangle, PaintUtils.ScaleRect( ClientRectangle, Image.Size ).Size );
            g.DrawImage( Image, drawingRect, 0, 0, Image.Width, Image.Height, GraphicsUnit.Pixel );         
        }

        base.OnPaint( e );
    }
}