C#图片按比例缩放实例

using System;using System.Collections.Generic;using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ZoomImage.Utils{ /// <summary> /// 图片缩放 /// </summary> public class ZoomImageUtil {  /// <summary>  /// 图片缩放  /// </summary>  /// <param name="bmp">图片</param>  /// <param name="width">目标宽度，若为0，表示宽度按比例缩放</param>  /// <param name="height">目标长度，若为0，表示长度按比例缩放</param>  public static Bitmap GetThumbnail(Bitmap bmp, int width, int height)  {   if (width == 0)   {    width = height * bmp.Width / bmp.Height;   }   if (height == 0)   {    height = width * bmp.Height / bmp.Width;   }   Image imgSource = bmp;   Bitmap outBmp = new Bitmap(width, height);   Graphics g = Graphics.FromImage(outBmp);   g.Clear(Color.Transparent);   // 设置画布的描绘质量      g.CompositingQuality = CompositingQuality.HighQuality;   g.SmoothingMode = SmoothingMode.HighQuality;   g.InterpolationMode = InterpolationMode.HighQualityBicubic;   g.DrawImage(imgSource, new Rectangle(0, 0, width, height + 1), 0, 0, imgSource.Width, imgSource.Height, GraphicsUnit.Pixel);   g.Dispose();   imgSource.Dispose();   bmp.Dispose();   return outBmp;  } }}

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.IO;using System.Linq;using System.Text;using System.Threading;using System.Threading.Tasks;using System.Windows.Forms;using ZoomImage.Utils;namespace ZoomImage{ public partial class Form1 : Form {  public Form1()  {   InitializeComponent();  }  private void Form1_Load(object sender, EventArgs e)  {   openFileDialog1.Multiselect = true;  }  private void txtWidth_KeyPress(object sender, KeyPressEventArgs e)  {   if (e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))   {    e.Handled = true;   }  }  private void txtHeight_KeyPress(object sender, KeyPressEventArgs e)  {   if (e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))   {    e.Handled = true;   }  }  private void btnSelectImage_Click(object sender, EventArgs e)  {   try   {    if (txtWidth.Text == "" && txtHeight.Text == "")    {     return;    }    if (openFileDialog1.ShowDialog() == DialogResult.OK)    {     Task.Factory.StartNew(() =>     {      string path = Path.GetDirectoryName(openFileDialog1.FileNames[0]) + "//NewImage//";      int i = 0;      foreach (string fileName in openFileDialog1.FileNames)      {       Bitmap bmp = ZoomImageUtil.GetThumbnail(new Bitmap(fileName), Convert.ToInt32(txtWidth.Text == "" ? "0" : txtWidth.Text), Convert.ToInt32(txtHeight.Text == "" ? "0" : txtHeight.Text));       if (!Directory.Exists(path))       {        Directory.CreateDirectory(path);       }       File.Delete(path + Path.GetFileName(fileName));       bmp.Save(path + Path.GetFileName(fileName));       this.Invoke(new InvokeDelegate(() =>       {        lblProgress.Text = string.Format("进度：{1}/{0}", openFileDialog1.FileNames.Length, ++i);       }));       Thread.Sleep(1);      }      MessageBox.Show("成功！");     });    }   }   catch (Exception ex)   {    MessageBox.Show(ex.Message);   }  } } /// <summary> /// 跨线程访问控件的委托 /// </summary> public delegate void InvokeDelegate();}