C#图片按比例缩放实例

usingSystem;

usingSystem.Collections.Generic;

usingSystem.Drawing;

usingSystem.Drawing.Drawing2D;

usingSystem.Drawing.Imaging;

usingSystem.Linq;

usingSystem.Text;

usingSystem.Threading.Tasks;

namespaceZoomImage.Utils

{

 ///

 publicclassZoomImageUtil

 {

  ///

  /// 图片

  /// 目标宽度，若为0，表示宽度按比例缩放

  /// 目标长度，若为0，表示长度按比例缩放

  publicstaticBitmap GetThumbnail(Bitmap bmp,intwidth,intheight)

  {

   if(width == 0)

   {

    width = height * bmp.Width / bmp.Height;

   }

   if(height == 0)

   {

    height = width * bmp.Height / bmp.Width;

   }

   Image imgSource = bmp;

   Bitmap outBmp =newBitmap(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,newRectangle(0, 0, width, height + 1), 0, 0, imgSource.Width, imgSource.Height, GraphicsUnit.Pixel);

   g.Dispose();

   imgSource.Dispose();

   bmp.Dispose();

   returnoutBmp;

  }

 }

}

usingSystem;

usingSystem.Collections.Generic;

usingSystem.ComponentModel;

usingSystem.Data;

usingSystem.Drawing;

usingSystem.IO;

usingSystem.Linq;

usingSystem.Text;

usingSystem.Threading;

usingSystem.Threading.Tasks;

usingSystem.Windows.Forms;

usingZoomImage.Utils;

namespaceZoomImage

{

 publicpartialclassForm1 : Form

 {

  publicForm1()

  {

   InitializeComponent();

  }

  privatevoidForm1_Load(objectsender, EventArgs e)

  {

   openFileDialog1.Multiselect =true;

  }

  privatevoidtxtWidth_KeyPress(objectsender, KeyPressEventArgs e)

  {

   if(e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))

   {

    e.Handled =true;

   }

  }

  privatevoidtxtHeight_KeyPress(objectsender, KeyPressEventArgs e)

  {

   if(e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))

   {

    e.Handled =true;

   }

  }

  privatevoidbtnSelectImage_Click(objectsender, EventArgs e)

  {

   try

   {

    if(txtWidth.Text ==""&& txtHeight.Text =="")

    {

     return;

    }

    if(openFileDialog1.ShowDialog() == DialogResult.OK)

    {

     Task.Factory.StartNew(() =>

     {

      stringpath = Path.GetDirectoryName(openFileDialog1.FileNames[0]) +"\NewImage\";

      inti = 0;

      foreach(stringfileNameinopenFileDialog1.FileNames)

      {

       Bitmap  bmp = ZoomImageUtil.GetThumbnail(newBitmap(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(newInvokeDelegate(() =>

       {

        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);

   }

  }

 }

 ///

 publicdelegatevoidInvokeDelegate();

}