并行c#线程性能问题

Question

此代码用于从彩色转换为黑白.

• 我试图在代码中添加并行部分
• 只是从灰度转变为黑白
• 我试图给每个线程分配一些像素数量的cols

但性能根本没有改善.

我通过在2 for循环和计数器值增量中更改除数值(其代码为800)来尝试获得800*600图像.

此更改应使线程数增加或减少

结果 :

value |  num of thread |   time
 800       1              1.17 sec
 400       2              1.17 sec
 200       4              1.17 sec
and so on ...

帮助我提高性能因为更大的图像需要8秒,我想让它平行

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Threading;

namespace IMG
{

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    string path = "";
    public void openimage()
    {
        if (openFileDialog1.ShowDialog() == DialogResult.OK)
        {
            path = openFileDialog1.FileName;
        }
    }
    Bitmap bm;
    Bitmap gs;
    private void button1_Click(object sender, EventArgs e)
    {
        if (path == "")
        {
            openimage();
        }
        Graphics g = this.CreateGraphics();
        bm = new Bitmap(path);
        // Draw image with no effects.....
        g.DrawImage(bm, 100, 100, 200, 200);
        gs = new Bitmap(bm.Width, bm.Height);
        worker soso = new worker(gs, bm);
        worker.counter = 0;
        soso.tograyscale();
        // Draw gray image.......
        g.DrawImage(gs, 305, 100, 200, 200);
        DateTime x = DateTime.Now;
        for (int koko = 0; koko < gs.Width/400; koko++)
        {        
                Thread t1 = new Thread(new ThreadStart(soso.trasform));
                t1.Start();
                t1.Join();
                soso.increment();
        }
        g.DrawImage(bm, 510, 100, 200, 200);
        gs.Dispose();
        g.Dispose();
        textBox19.Text=(DateTime.Now - x).ToString();
    }
}
public class worker
{
    public static int counter = 0;
    public Bitmap gs;
    public Bitmap bm;
    public int xxxx;
    public worker(Bitmap a, Bitmap b)
    {
        gs = a;
        bm = b;
        xxxx = a.Height;
    }
    public void increment()
    {
        counter += 400;
    }
    public void trasform()
    {
        argtransform(counter);

    }
    public void tograyscale()
    {
        for (int i = 0; i < bm.Width; i++)
        {
            for (int j = 0; j < bm.Height; j++)
            {
                Color c = bm.GetPixel(i, j);
                int y = (int)(0.3 * c.R + 0.59 * c.G + 0.11 * c.B);
                gs.SetPixel(i, j, Color.FromArgb(y, y, y));
            }
        }
    }
    public void argtransform(int cc)
    {
        for (int i = cc; i < cc + 400; i++)
        {
            for (int j = 0; j < xxxx; j++)
            {
                Color c = gs.GetPixel(i, j);
                int y1 = 0;
                if (c.R >= 128)
                    y1 = 255;
                bm.SetPixel(i, j, Color.FromArgb(y1, y1, y1));
            }
        }
    }
  }
}

谢谢你,请尽快

---

谢谢Craig Stuntz的所有问题:如何在不调用setpixel的情况下编辑像素的颜色？谢谢您的帮助

Answer 1

在优化之前不要并行化.在优秀的分析器下运行代码并首先解决性能问题.是的,这最终可能会成为并行化的良好候选者,但我认为100万次呼叫SetPixel是一个更大的问题.