C#生成缩略图-阿南达文事网

C#生成缩略图

/**/ /// <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(); }

int towidth = width; int toheight = height;

int x = 0; int y = 0; int ow = originalImage.Width; int oh = originalImage.Height;

//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);

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

image.Save(Path_sy); image.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();

本文参与腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。原始发表：2012-03-20，如有侵权请联系 cloudcommunity@tencent 删除system对象服务器c#drawing

C#生成缩略图