缩略图的压缩问题

如果宽度固定，高度等比例压缩的话，如何计算高度的问题：

string originalImagePath；//原图的路径

System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

1.指定宽，高按比例 缩放           
  int    toheight = originalImage.Height * width / originalImage.Width; 

2.指定高，宽按比例
  int  towidth = originalImage.Width * height / originalImage.Height;

3.如果指定宽、高

 private static Size ResizeImage(int width, int height, int maxWidth, int maxHeight)   

      {       

     decimal MAX_WIDTH = (decimal)maxWidth;     

        decimal MAX_HEIGHT = (decimal)maxHeight;       

      decimal ASPECT_RATIO = MAX_WIDTH / MAX_HEIGHT;

            int newWidth, newHeight;        

     decimal originalWidth = (decimal)width;     

        decimal originalHeight = (decimal)height;

            if (originalWidth > MAX_WIDTH || originalHeight > MAX_HEIGHT)        

     {                

        decimal factor;            

         if (originalWidth / originalHeight > ASPECT_RATIO)      

           {                 

             factor = originalWidth / MAX_WIDTH;            

         newWidth = Convert.ToInt32(originalWidth / factor);           

          newHeight = Convert.ToInt32(originalHeight / factor);        

         }           

      else             

    {                   

  factor = originalHeight / MAX_HEIGHT;      

               newWidth = Convert.ToInt32(originalWidth / factor);       

              newHeight = Convert.ToInt32(originalHeight / factor);      

           }         

    }           

  else         

    {                

newWidth = width;      

           newHeight = height;       

      }           

  return new Size(newWidth, newHeight);  

       }

最后缩略成功