#region 根据原图片生成等比缩略图
/// <summary>
/// 根据源图片生成缩略图
/// </summary>
/// <param name="imgPath_old">源图(大图)物理路径</param>
/// <param name="imgPath_new">缩略图物理路径(生成的缩略图将保存到该物理位置)</param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>
/// <param name="mode">缩略图缩放模式(取值"HW":指定高宽缩放,可能变形；取值"W":按指定宽度,高度按比例缩放；取值"H":按指定高度,宽度按比例缩放；取值"Cut":按指定高度和宽度裁剪,不变形)；取值"DB":等比缩放,以值较大的作为标准进行等比缩放</param>
/// <param name="type">即将生成缩略图的文件的扩展名(仅限：JPG、GIF、PNG、BMP)</param>
public static void MakeThumbnail(string imgPath_old, string imgPath_new, int width, int height, string mode, string imageType, int xx, int yy)
{
System.Drawing.Image img = System.Drawing.Image.FromFile(imgPath_old);
int towidth = width; int toheight = height;
int x = ; int y = ; int ow = img.Width;
int oh = img.Height; switch (mode)
{
case "HW": //指定高宽压缩
if ((double)img.Width / (double)img.Height > (double)width / (double)height)//判断图形是什么形状
{
towidth = width;
toheight = img.Height * width / img.Width;
}
else if ((double)img.Width / (double)img.Height == (double)width / (double)height)
{
towidth = width;
toheight = height;
}
else
{
toheight = height;
towidth = img.Width * height / img.Height;
}
break;
case "W": //指定宽，高按比例
toheight = img.Height * width / img.Width;
break;
case "H": //指定高，宽按比例
towidth = img.Width * height / img.Height;
break;
case "Cut": //指定高宽裁减（不变形）
if ((double)img.Width / (double)img.Height > (double)towidth / (double)toheight)
{
oh = img.Height;
ow = img.Height * towidth / toheight;
y = yy; x = (img.Width - ow) / ;
}
else
{
ow = img.Width;
oh = img.Width * height / towidth;
x = xx; y = (img.Height - oh) / ;
} break;
case "DB": // 按值较大的进行等比缩放（不变形）
if ((double)img.Width / (double)towidth < (double)img.Height / (double)toheight)
{
toheight = height;
towidth = img.Width * height / img.Height;
}
else
{
towidth = width;
toheight = img.Height * width / img.Width;
} break;
default:
break;
}
//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
//新建一个画板
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
//设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并以透明背景色填充
g.Clear(System.Drawing.Color.Transparent);
//在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(img, new System.Drawing.Rectangle(, , towidth, toheight),
new System.Drawing.Rectangle(x, y, ow, oh),
System.Drawing.GraphicsUnit.Pixel); try
{
//以jpg格式保存缩略图
switch (imageType.ToLower())
{
case "gif":
img.Save(imgPath_new, ImageFormat.Jpeg);//生成缩略图
break;
case "jpg":
bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Jpeg);
break;
case "bmp":
bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Bmp);
break;
case "png":
bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Png);
break;
default:
bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Jpeg);
break;
}
////保存缩略图
// bitmap.Save(imgPath_new);
}
catch (System.Exception e)
{
throw e;
}
finally
{
img.Dispose();
bitmap.Dispose(); g.Dispose();
}
}
#endregion