加速位图灰度转换,OpenMP是C#中的一个选项吗？

发布时间：2020-12-16 01:20:52 所属栏目：百科来源：网络整理

导读：请帮我用openmp使这段代码并行此代码在按钮单击时运行,文本框为128 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

请帮我用openmp使这段代码并行
此代码在按钮单击时运行,文本框为128

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;

namespace IMG
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    string path = "";
    public void openimage()
    {
        if (openFileDialog1.ShowDialog() == DialogResult.OK)
        {
            path = openFileDialog1.FileName;
            Graphics g = this.CreateGraphics();
            g.Clear(this.BackColor);
            Bitmap curBitmap = new Bitmap(path);
            g.DrawImage(curBitmap,200,220,200);
        }
    }
    Bitmap bm;
    Bitmap gs;
    private void button1_Click(object sender,EventArgs e)
    {
        if (path == "")
        {
            openimage();
        }

        //mack image gray scale
        Graphics g = this.CreateGraphics();
        g.Clear(this.BackColor);
        // Create a Bitmap object
        bm = new Bitmap(path);
        // Draw image with no effects
        g.DrawImage(bm,200);


        gs = new Bitmap(bm.Width,bm.Height);
        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));
            }
        }

        // Draw image with no effects
        g.DrawImage(gs,405,200);


        for (int i = 0; i < gs.Width; i++)
        {
            for (int j = 0; j < gs.Height; j++)
            {
                Color c = gs.GetPixel(i,j);
                int y1 = 0;

                if (c.R >= Convert.ToInt16(textBox19.Text))
                    y1 = 255;
                bm.SetPixel(i,Color.FromArgb(y1,y1,y1));

            }
        }
        g.DrawImage(bm,new Rectangle(610,200),bm.Width,bm.Height,GraphicsUnit.Pixel);
        // Dispose of objects
        gs.Dispose();

        g.Dispose();
    }
 }
}

一旦你能相信这个网站和所有程序员,请尽快帮助我……

解决方法

如果OpenMP在您的雷达上,您将遇到几个速度障碍. OpenMP是一个用于非托管C/C++的多线程库,它需要编译器支持才能生效.不是C#的选项.

我们退一步吧.你现在得到的就像你可能得到的一样糟糕. Get / SetPixel()非常慢.一个主要步骤是使用Bitmap.LockBits(),它为位图位提供IntPtr.您可以使用不安全的字节指针对这些位进行聚会.这将至少快一个数量级.

让我们再退一步,你清楚地编写代码将彩色图像转换为灰度图像. GDI通过ColorMatrix类本身支持颜色转换.该代码可能如下所示：

public static Image ConvertToGrayScale(Image srce) {
  Bitmap bmp = new Bitmap(srce.Width,srce.Height);
  using (Graphics gr = Graphics.FromImage(bmp)) {
    var matrix = new float[][] {
        new float[] { 0.299f,0.299f,0 },new float[] { 0.587f,0.587f,new float[] { 0.114f,0.114f,new float[] { 0,1,1 }
    };
    var ia = new System.Drawing.Imaging.ImageAttributes();
    ia.SetColorMatrix(new System.Drawing.Imaging.ColorMatrix(matrix));
    var rc = new Rectangle(0,srce.Width,srce.Height);
    gr.DrawImage(srce,rc,srce.Height,GraphicsUnit.Pixel,ia);
    return bmp;
  }
}

上述代码归功于Bob Powell.

（编辑：李大同）

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