图片缩略图

生成缩略图2

public void SmallPic(string strOldPic, string strNewPic, int intWidth,int intHeight,bool deletl)
    {
        System.Drawing.Bitmap objPic, objNewPic;
        objPic = new System.Drawing.Bitmap(strOldPic);
             int newwidth= ResizeImage(objPic.Width, objPic.Height, intWidth, intHeight);
           int newheight = ResizeImagehig(objPic.Width, objPic.Height, intWidth, intHeight);
                objNewPic = new System.Drawing.Bitmap(objPic, newwidth, newheight);
                objNewPic.Save(strNewPic);
        objPic.Dispose();
        objNewPic.Dispose();
        objPic = null;
        objNewPic = null;
        if (deletl == true)
        {
            File.Delete(strOldPic);
        }
    }
    /**/
    /// <summary>
    /// 计算新宽度
    /// </summary>
    /// <param name="width">原始宽度</param>
    /// <param name="height">原始高度</param>
    /// <param name="maxWidth">最大新宽度</param>
    /// <param name="maxHeight">最大新高度</param>
    /// <returns></returns>
    private int 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;
            // determine the largest 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 newWidth;
    }
    private int ResizeImagehig(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;
            // determine the largest 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 newHeight;
    }