C#实现图片旋转的代码

#region 图片旋转函数

/// <summary>

/// 以逆时针为方向对图像进行旋转

/// </summary>

/// <param name="b">位图流</param>

/// <param name="angle">旋转角度[-360,360](前台给的) 正负代表方向</param>

/// <returns></returns>

public Bitmap Rotate(Bitmap b, int angle)

{

angle = angle % 360; //弧度转换

double radian = angle * Math.PI / 180.0;

double cos = Math.Cos(radian);

double sin = Math.Sin(radian);

//原图的宽和高

int w = b.Width;

int h = b.Height;

int W = (int)(Math.Max(Math.Abs(w * cos - h * sin), Math.Abs(w * cos + h * sin)));

int H = (int)(Math.Max(Math.Abs(w * sin - h * cos), Math.Abs(w * sin + h * cos)));

//目标位图

Bitmap dsImage = new Bitmap(W, H);

System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(dsImage);

g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Bilinear;

g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

//计算偏移量

Point Offset = new Point((W - w) / 2, (H - h) / 2);

//构造图像显示区域：让图像的中心与窗口的中心点一致

Rectangle rect = new Rectangle(Offset.X, Offset.Y, w, h);

Point center = new Point(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);

g.TranslateTransform(center.X, center.Y);

g.RotateTransform(360 - angle);

//恢复图像在水平和垂直方向的平移

g.TranslateTransform(-center.X, -center.Y);

g.DrawImage(b, rect);

//重至绘图的所有变换

g.ResetTransform();

g.Save();

g.Dispose();

//dsImage.Save("yuancd.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

return dsImage;

}

#endregion 图片旋转函数