如何正確地使用asp.net旋轉圖像？

Question

我想用asp.net旋轉圖像。我使用了TranslateTransform和RotateTransform。旋轉後，圖像被損壞。我怎麼解決這個問題？

Answer 1

這裏是一個鏈接，顯示如何使用System.Drawing中正確地做到這一點：

http://forums.asp.net/p/1234460/2239261.aspx

相關代碼從post：

public Bitmap RotateBitmap(float Angle, Bitmap bm_in) 
{ 
    try 
    { 
     float wid = bm_in.Width; 
     float hgt = bm_in.Height; 
     Point[] corners = { new Point(0, 0), new Point(int.Parse(wid.ToString()), 0), new Point(0, int.Parse(hgt.ToString())), new Point(int.Parse(wid.ToString()), int.Parse(hgt.ToString())) }; 
     int cx = int.Parse(wid.ToString())/2; 
     int cy = int.Parse(hgt.ToString())/2; 
     long i; 
     for (i = 0; i <= 3; i++) 
     { 
      corners[i].X -= Convert.ToInt32(cx.ToString()); 
      corners[i].Y -= Convert.ToInt32(cy.ToString()); 
     } 

     float theta = (float)(Angle * Math.PI/180.0); 
     float sin_theta = (float)Math.Sin(theta); 
     float cos_theta = (float)Math.Cos(theta); 
     float X; 
     float Y; 
     for (i = 0; i <= 3; i++) 
     { 
      X = corners[i].X; 
      Y = corners[i].Y; 
      corners[i].X = (int)(X * cos_theta + Y * sin_theta); 
      corners[i].Y = (int)(-X * sin_theta + Y * cos_theta); 
     } 

     float xmin = corners[0].X; 
     float ymin = corners[0].Y; 
     for (i = 1; i <= 3; i++) 
     { 
      if (xmin > corners[i].X) 
       xmin = corners[i].X; 
      if (ymin > corners[i].Y) 
       ymin = corners[i].Y; 
     } 
     for (i = 0; i <= 3; i++) 
     { 
      corners[i].X -= int.Parse(xmin.ToString()); 
      corners[i].Y -= int.Parse(ymin.ToString()); 
     } 

     Bitmap bm_out = new Bitmap((int)(-2 * xmin), (int)(-2 * ymin)); 
     Graphics gr_out = Graphics.FromImage(bm_out); 
     // ERROR: Not supported in C#: ReDimStatement 
     Point[] temp = new Point[3]; 
     if (corners != null) 
     { 
      Array.Copy(corners, temp, Math.Min(corners.Length, temp.Length)); 
     } 
     corners = temp; 
     gr_out.DrawImage(bm_in, corners); 
     return bm_out; 
    } 
    catch (Exception ex) 
    { 
     string s = ex.Message; 
     return bm_in; 
    } 
}