C#的影象裁剪很容易操作,這裡給個實現的例子

關鍵是需要處理滑鼠的事件和一些更新

實現滑鼠移動的程式碼.注意更新不要全部重畫,只有選擇矩形部分重畫

  private void Form1_MouseMove(object sender, MouseEventArgs e)
        {

            if (Track_move)
                endpoint = new Point(e.X, e.Y);
            else
            {
                return;
            }
            rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);

            Rectangle tempr = new Rectangle(rect1.X, rect1.Y, rect1.Width + 2, rect1.Height + 2);
            this.Invalidate(tempr);
        }

選擇結束的處理程式碼.

  private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left && Track_move==true )
            {
                Track_move = false;
                endpoint = new Point(e.X, e.Y);
                rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);
                Rectangle rectorg = new Rectangle(borg.X, borg.Y, image1.Width, image1.Height);
                if (rect1.Width <= 0)
                    return;
                if (rect1.Height <= 0)
                    return;
                if (rectorg.Contains(rect1))
                {
                    Rectangle rectadj = new Rectangle(rect1.X - borg.X, rect1.Y - borg.Y, rect1.Width, rect1.Height);
                    Bitmap cropimge = image1.Clone(rectadj, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
                    pictureBox2.Image = cropimge;
                }
                else
                {
                    pictureBox2.Image = null;
                }
                this.Invalidate();
            }
        }

程式的整個程式碼

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.Runtime.InteropServices;

namespace imageForms
{
    static class Program
    {
        /// <summary>
        /// 應用程式的主入口點。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
    public partial class Form1 : Form
    {
        private System.Windows.Forms.PictureBox pictureBox2;
        private System.Windows.Forms.Label label1;
        public Form1()
        {
            InitializeComponent();
        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            showimg();

        }
        Bitmap image1;
        private void showimg()
        {
            int wd = 400;
            int hg = 200;
            int len = wd * hg * 3;
            byte[] pdata = new byte[len];
            for (int i = 0; i < len; i++)
            {
                if (i > 3 * wd * (hg / 2))
                {
                    pdata[i] = 255;
                }
                else
                {
                    pdata[i] = 0;
                }
            }

            try
            {
                image1 = new Bitmap(wd, hg, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
                for (int y = 0; y < hg; y++)
                {
                    for (int x = 0; x < wd; x++)
                    {
                        Color crr = Color.FromArgb(pdata[3 * wd * y + x], pdata[3 * wd * y + x], pdata[3 * wd * y + x]);
                        image1.SetPixel(x, y, crr);
                    }
                }
                // Set the PictureBox to display the image.
              //  pictureBox1.Image = image1;

            }
            catch (ArgumentException)
            {
                MessageBox.Show("There was an error check data.");
            }
        }
        Point stpoint,endpoint;    
        Rectangle rect1;     
        Point borg = new Point(20, 20);
        protected override void  OnPaint(PaintEventArgs e)
        {
         
            base.OnPaint(e);
             e.Graphics.DrawImage(image1, borg);
             if (rect1 != null )
             {
                 e.Graphics.DrawRectangle(new Pen(Color.Red, 1), rect1);
             }
        
        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                stpoint = new Point(e.X, e.Y);
                Track_move = true;
                return;
            }
            Track_move = false;
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left && Track_move==true )
            {
                Track_move = false;
                endpoint = new Point(e.X, e.Y);
                rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);
                Rectangle rectorg = new Rectangle(borg.X, borg.Y, image1.Width, image1.Height);
                if (rect1.Width <= 0)
                    return;
                if (rect1.Height <= 0)
                    return;
                if (rectorg.Contains(rect1))
                {
                    Rectangle rectadj = new Rectangle(rect1.X - borg.X, rect1.Y - borg.Y, rect1.Width, rect1.Height);
                    Bitmap cropimge = image1.Clone(rectadj, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
                    pictureBox2.Image = cropimge;
                }
                else
                {
                    pictureBox2.Image = null;
                }
                this.Invalidate();
            }
        }
        bool Track_move=false ;
        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {

            if (Track_move)
                endpoint = new Point(e.X, e.Y);
            else
            {
                return;
            }
            rect1 = new Rectangle(stpoint.X, stpoint.Y, endpoint.X - stpoint.X, endpoint.Y - stpoint.Y);

            Rectangle tempr = new Rectangle(rect1.X, rect1.Y, rect1.Width + 2, rect1.Height + 2);
            this.Invalidate(tempr);
        }
        private System.ComponentModel.IContainer components = null;

        private void InitializeComponent()
        {
            this.pictureBox2 = new System.Windows.Forms.PictureBox();
            this.label1 = new System.Windows.Forms.Label();
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox2)).BeginInit();
            this.SuspendLayout();
            //
            // pictureBox2
            //
            this.pictureBox2.Location = new System.Drawing.Point(605, 103);
            this.pictureBox2.Name = "pictureBox2";
            this.pictureBox2.Size = new System.Drawing.Size(227, 173);
            this.pictureBox2.TabIndex = 1;
            this.pictureBox2.TabStop = false;
            //
            // label1
            //
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(602, 58);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(127, 15);
            this.label1.TabIndex = 2;
            this.label1.Text = "滑鼠左鍵選擇裁剪";
            //
            // Form1
            //
            this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 15F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(844, 558);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.pictureBox2);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.MouseUp += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseUp);
            this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown);
            this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseMove);
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox2)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

    }
}