C#图片按比例缩放

Posted 2020-06-19

  // 按比例缩放图片
          public Image ZoomPicture(Image SourceImage, int TargetWidth, int TargetHeight)
          {
              int IntWidth; //新的图片宽
              int IntHeight; //新的图片高
              try
              {
                  System.Drawing.Imaging.ImageFormat format = SourceImage.RawFormat;
                  System.Drawing.Bitmap SaveImage = new System.Drawing.Bitmap(TargetWidth, TargetHeight);
                 Graphics g = Graphics.FromImage(SaveImage);
                 g.Clear(Color.White);
 
 
                 if (SourceImage.Width > TargetWidth && SourceImage.Height <= TargetHeight)//宽度比目的图片宽度大，长度比目的图片长度小
                 {
                     IntWidth = TargetWidth;
                     IntHeight = (IntWidth * SourceImage.Height) / SourceImage.Width;
                 }
                 else if (SourceImage.Width <= TargetWidth && SourceImage.Height > TargetHeight)//宽度比目的图片宽度小，长度比目的图片长度大
                 {
                     IntHeight = TargetHeight;
                     IntWidth = (IntHeight * SourceImage.Width) / SourceImage.Height;
                 }
                 else if (SourceImage.Width <= TargetWidth && SourceImage.Height <= TargetHeight) //长宽比目的图片长宽都小
                 {
                     IntHeight = SourceImage.Width;
                     IntWidth = SourceImage.Height;
                 }
                 else//长宽比目的图片的长宽都大
                 {
                     IntWidth = TargetWidth;
                     IntHeight = (IntWidth * SourceImage.Height) / SourceImage.Width;
                     if (IntHeight > TargetHeight)//重新计算
                     {
                         IntHeight = TargetHeight;
                         IntWidth = (IntHeight * SourceImage.Width) / SourceImage.Height;
                     }
                 }
 
                 g.DrawImage(SourceImage, (TargetWidth - IntWidth) / 2, (TargetHeight - IntHeight) / 2, IntWidth, IntHeight);
                 SourceImage.Dispose();
 
                 return SaveImage;
             }
             catch (Exception ex)
             {
               
             }
 
             return null;
         }