C#生成缩略图-白红宇

C#生成缩略图

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发布时间：2019-06-09

本文共 9390 字，大约阅读时间需要 31 分钟。

/**/

/// <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();

}

/**/

/// <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.Dispose();

image.Save(Path_syp);

image.Dispose();

}

一步一步来创建高质量的缩略图：

本例中假定了两个变量：

String src="c:/myImages/a.jpg"; //源图像文件的绝对路径

String dest="c:/myImages/a_th.jpg"; //生成的缩略图图像文件的绝对路径

int thumbWidth=132; //要生成的缩略图的宽度

下面通过ASP .NET C#来演示代码片段：

你应该包含这些名称空间

using System.Drawing;

using System.Drawing.Drawing2D

System.Drawing.Image image = System.Drawing.Image.FromFile(src); //利用Image对象装载源图像

//接着创建一个System.Drawing.Bitmap对象，并设置你希望的缩略图的宽度和高度。

int srcWidth=image.Width;

int srcHeight=image.Height;

int thumbHeight=(srcHeight/srcWidth)*thumbWidth;

Bitmap bmp = new Bitmap(thumbWidth, thumbHeight);

//从Bitmap创建一个System.Drawing.Graphics对象，用来绘制高质量的缩小图。

System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp);

//设置 System.Drawing.Graphics对象的SmoothingMode属性为HighQuality

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

//下面这个也设成高质量

gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;

//下面这个设成High

gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

//把原始图像绘制成上面所设置宽高的缩小图

System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, thumbWidth, thumbHeight);

gr.DrawImage(image, rectDestination, 0, 0, srcWidth, srcHeight, GraphicsUnit.Pixel);

//保存图像，大功告成！

bmp.Save(dest);

//最后别忘了释放资源（译者PS：C#可以自动回收吧）

bmp.Dispose();

image.Dispose();

转载于:https://www.cnblogs.com/BlogNetSpace/archive/2012/03/20/1557255.html

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