C#生成图片缩略图、水印及上传的几个通用方法

/// <summary>

/// 获取一个图片按等比例缩小后的大小。

/// </summary>

/// <param name="maxWidth">需要缩小到的宽度</param>

/// <param name="maxHeight">需要缩小到的高度</param>

/// <param name="imageOriginalWidth">图片的原始宽度</param>

/// <param name="imageOriginalHeight">图片的原始高度</param>

/// <returns>返回图片按等比例缩小后的实际大小</returns>

public static Size GetNewSize(int maxWidth, int maxHeight, int imageOriginalWidth, int imageOriginalHeight)

{

double w = 0.0;

double h = 0.0;

double sw = Convert.ToDouble(imageOriginalWidth);

double sh = Convert.ToDouble(imageOriginalHeight); double mw = Convert.ToDouble(maxWidth);

double mh = Convert.ToDouble(maxHeight);

if (sw < mw && sh < mh)

{

w = sw;

h = sh;

}

else if ((sw / sh) > (mw / mh))

{

w = maxWidth;

h = (w * sh) / sw;

}

else

{

h = maxHeight;

w = (h * sw) / sh;

}

return new Size(Convert.ToInt32(w), Convert.ToInt32(h));

}

/// <summary>

/// 对给定的一个图片（Image对象）生成一个指定大小的缩略图。

/// </summary>

/// <param name="originalImage">原始图片</param>

/// <param name="thumMaxWidth">缩略图的宽度</param>

/// <param name="thumMaxHeight">缩略图的高度</param>

/// <returns>返回缩略图的Image对象</returns>

public static System.Drawing.Image GetThumbNailImage(System.Drawing.Image originalImage, int thumMaxWidth, int thumMaxHeight)

{

Size thumRealSize = Size.Empty;

System.Drawing.Image newImage = originalImage;

Graphics graphics = null;

try

{

thumRealSize = GetNewSize(thumMaxWidth, thumMaxHeight, originalImage.Width, originalImage.Height);

newImage = new Bitmap(thumRealSize.Width, thumRealSize.Height);

graphics = Graphics.FromImage(newImage);

graphics.CompositingQuality = CompositingQuality.HighQuality;

graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;

graphics.SmoothingMode = SmoothingMode.HighQuality;

graphics.Clear(Color.Transparent);

graphics.DrawImage(originalImage, new Rectangle(0, 0, thumRealSize.Width, thumRealSize.Height), new Rectangle(0, 0, originalImage.Width, originalImage.Height), GraphicsUnit.Pixel);

}

catch { }

finally

{

if (graphics != null)

{

graphics.Dispose();

graphics = null;

}

}

return newImage;

}

/// <summary>

/// 对给定的一个图片文件生成一个指定大小的缩略图。

/// </summary>

/// <param name="originalImage">图片的物理文件地址</param>

/// <param name="thumMaxWidth">缩略图的宽度</param>

/// <param name="thumMaxHeight">缩略图的高度</param>

/// <returns>返回缩略图的Image对象</returns>

public static System.Drawing.Image GetThumbNailImage(string imageFile, int thumMaxWidth, int thumMaxHeight)

{

System.Drawing.Image originalImage = null;

System.Drawing.Image newImage = null;

try

{

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

newImage = GetThumbNailImage(originalImage, thumMaxWidth, thumMaxHeight);

}

catch { }

finally

{

if (originalImage != null)

{

originalImage.Dispose();

originalImage = null;

}

}

return newImage;

}

/// <summary>

/// 对给定的一个图片文件生成一个指定大小的缩略图，并将缩略图保存到指定位置。

/// </summary>

/// <param name="originalImageFile">图片的物理文件地址</param>

/// <param name="thumbNailImageFile">缩略图的物理文件地址</param>

/// <param name="thumMaxWidth">缩略图的宽度</param>

/// <param name="thumMaxHeight">缩略图的高度</param>

public static void MakeThumbNail(string originalImageFile, string thumbNailImageFile, int thumMaxWidth, int thumMaxHeight)

{

System.Drawing.Image newImage = GetThumbNailImage(originalImageFile, thumMaxWidth, thumMaxHeight);

try

{

newImage.Save(thumbNailImageFile, ImageFormat.Jpeg);

}

catch

{ }

finally

{

newImage.Dispose();

newImage = null;

}

}

/// <summary>

/// 将一个图片的内存流调整为指定大小，并返回调整后的内存流。

/// </summary>

/// <param name="originalImageStream">原始图片的内存流</param>

/// <param name="newWidth">新图片的宽度</param>

/// <param name="newHeight">新图片的高度</param>

/// <returns>返回调整后的图片的内存流</returns>

public static MemoryStream ResizeImage(Stream originalImageStream, int newWidth, int newHeight)

{

MemoryStream newImageStream = null;

System.Drawing.Image newImage = Globals.GetThumbNailImage(System.Drawing.Image.FromStream(originalImageStream), newWidth, newHeight);

if (newImage != null)

{

newImageStream = new MemoryStream();

newImage.Save(newImageStream, ImageFormat.Jpeg);

}

return newImageStream;

}

/// <summary>

/// 将一个内存流保存为磁盘文件。

/// </summary>

/// <param name="stream">内存流</param>

/// <param name="newFile">目标磁盘文件地址</param>

public static void SaveStreamToFile(Stream stream, string newFile)

{

if (stream == null || stream.Length == 0 || string.IsNullOrEmpty(newFile))

{

return;

}

byte[] buffer = new byte[stream.Length];

stream.Position = 0;

stream.Read(buffer, 0, buffer.Length);

FileStream fileStream = new FileStream(newFile, FileMode.OpenOrCreate, FileAccess.Write);

fileStream.Write(buffer, 0, buffer.Length);

fileStream.Flush();

fileStream.Close();

fileStream.Dispose();

}

/// <summary>

/// 对一个指定的图片加上图片水印效果。

/// </summary>

/// <param name="imageFile">图片文件地址</param>

/// <param name="waterImage">水印图片（Image对象）</param>

public static void CreateImageWaterMark(string imageFile, System.Drawing.Image waterImage)

{

if (string.IsNullOrEmpty(imageFile) || !File.Exists(imageFile) || waterImage == null)

{

return;

}

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

if (originalImage.Width - 10 < waterImage.Width || originalImage.Height - 10 < waterImage.Height)

{

return;

}

Graphics graphics = Graphics.FromImage(originalImage);

int x = originalImage.Width - waterImage.Width - 10;

int y = originalImage.Height - waterImage.Height - 10;

int width = waterImage.Width;

int height = waterImage.Height;

graphics.DrawImage(waterImage, new Rectangle(x, y, width, height), 0, 0, width, height, GraphicsUnit.Pixel);

graphics.Dispose();

MemoryStream stream = new MemoryStream();

originalImage.Save(stream, ImageFormat.Jpeg);

originalImage.Dispose();

System.Drawing.Image imageWithWater = System.Drawing.Image.FromStream(stream);

imageWithWater.Save(imageFile);

imageWithWater.Dispose();

}

/// <summary>

/// 对一个指定的图片加上文字水印效果。

/// </summary>

/// <param name="imageFile">图片文件地址</param>

/// <param name="waterText">水印文字内容</param>

public static void CreateTextWaterMark(string imageFile, string waterText)

{

if (string.IsNullOrEmpty(imageFile) || string.IsNullOrEmpty(waterText) || !File.Exists(imageFile))

{

return;

}

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

Graphics graphics = Graphics.FromImage(originalImage);

graphics.SmoothingMode = SmoothingMode.HighQuality;

graphics.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;

graphics.CompositingQuality = CompositingQuality.HighQuality;

graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;

SolidBrush brush = new SolidBrush(Color.FromArgb(153, 255, 255, 255));

Font waterTextFont = new Font("Arial", 16, FontStyle.Regular);

SizeF waterTextSize = graphics.MeasureString(waterText, waterTextFont);

float x = (float)originalImage.Width - waterTextSize.Width - 10F;

float y = (float)originalImage.Height - waterTextSize.Height - 10F;

graphics.DrawString(waterText, waterTextFont, brush, x, y);

graphics.Dispose();

brush.Dispose();

MemoryStream stream = new MemoryStream();

originalImage.Save(stream, ImageFormat.Jpeg);

originalImage.Dispose();

System.Drawing.Image imageWithWater = System.Drawing.Image.FromStream(stream);

imageWithWater.Save(imageFile);

imageWithWater.Dispose();

}

/// <summary>

/// 判断上传组件是否包含内容。

/// </summary>

/// <param name="fileUpload">ASP.NET 2.0标准上传组件</param>

/// <returns>如果数据有效，则返回True，否则返回False</returns>

public static bool IsAttachmentValid(FileUpload fileUpload)

{

if (fileUpload != null &&

fileUpload.PostedFile != null &&

!string.IsNullOrEmpty(fileUpload.PostedFile.FileName) &&

fileUpload.PostedFile.ContentLength > 0)

{

return true;

}

return false;

}

转载：http://cnjmwr.blog.163.com/blog/static/1770070832011121103029169/