C#生成缩略图,加文字或图片水印

最近做东西,客户要求上传商品大图,自动生成缩略图,要求等比缩放,正好能在指定的大小内显示,(即如果高超出的比宽超出的多,就把高缩到指定高度,宽也等比缩放,反之宽也如此)

从网上找了如下代码(出处不明),但发现他的生成缩略图的方式有四种,但都不是我想要的,于是在上面加了case "DB"://等比缩放（不变形，如果高大按高，宽大按宽缩放） 这种方式实现了我想要的功能

/**/

/// <summary>

/// 生成缩略图

/// </summary>

/// <param name="originalImagePath">源图路径（物理路径）</param>

/// <param name="thumbnailPath">缩略图路径（物理路径）</param>

/// <param name="width">缩略图宽度</param>

/// <param name="height">缩略图高度</param>

/// <param name="mode">生成缩略图的方式</param>

public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode,string type)

{

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

int towidth = width;

int toheight = height;

int x = 0;

int y = 0;

int ow = originalImage.Width;

int oh = originalImage.Height;

switch (mode)

{

case "HW"://指定高宽缩放（可能变形）

break;

case "W"://指定宽，高按比例

toheight = originalImage.Height * width / originalImage.Width;

break;

case "H"://指定高，宽按比例

towidth = originalImage.Width * height / originalImage.Height;

break;

case "Cut"://指定高宽裁减（不变形）

if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)

{

oh = originalImage.Height;

ow = originalImage.Height * towidth / toheight;

y = 0;

x = (originalImage.Width - ow) / 2;

}

else

{

ow = originalImage.Width;

oh = originalImage.Width * height / towidth;

x = 0;

y = (originalImage.Height - oh) / 2;

}

break;

case "DB"://等比缩放（不变形，如果高大按高，宽大按宽缩放）

if ((double)originalImage.Width / (double)towidth < (double)originalImage.Height / (double)toheight)

{

toheight = height;

towidth = originalImage.Width * height / originalImage.Height;

}

else

{

towidth = width;

toheight = originalImage.Height * width / originalImage.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(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),

new System.Drawing.Rectangle(x, y, ow, oh),

System.Drawing.GraphicsUnit.Pixel);

try

{

//保存缩略图

if (type=="JPG")

{

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);

}

if (type=="BMP")

{

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);

}

if (type=="GIF")

{

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);

}

if (type=="PNG")

{

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);

}

}

catch (System.Exception e)

{

throw e;

}

finally

{

originalImage.Dispose();

bitmap.Dispose();

g.Dispose();

}

}

/**/

/// <summary>

/// 在图片上增加文字水印

/// </summary>

/// <param name="Path">原服务器图片路径</param>

/// <param name="Path_sy">生成的带文字水印的图片路径</param>

protected void AddShuiYinWord(string Path, string Path_sy)

{

string addText = "测试水印";

System.Drawing.Image image = System.Drawing.Image.FromFile(Path);

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

g.DrawImage(image, 0, 0, image.Width, image.Height);

System.Drawing.Font f = new System.Drawing.Font("Verdana", 16);

System.Drawing.Brush b = new System.Drawing.SolidBrush(System.Drawing.Color.Blue);

g.DrawString(addText, f, b, 15, 15);

g.Dispose();

image.Save(Path_sy);

image.Dispose();

}

/**/

/// <summary>

/// 在图片上生成图片水印

/// </summary>

/// <param name="Path">原服务器图片路径</param>

/// <param name="Path_syp">生成的带图片水印的图片路径</param>

/// <param name="Path_sypf">水印图片路径</param>

protected void AddShuiYinPic(string Path, string Path_syp, string Path_sypf)

{

System.Drawing.Image image = System.Drawing.Image.FromFile(Path);

System.Drawing.Image copyImage = System.Drawing.Image.FromFile(Path_sypf);

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

g.DrawImage(copyImage, new System.Drawing.Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, System.Drawing.GraphicsUnit.Pixel);

g.Dispose();

image.Save(Path_syp);

image.Dispose();

}