asp.net上传图片自动生成缩略图功能代码

?

if (FileUpload1.FileName.ToString() == "")

{

Label3.Text = "请选择图片！";

}

else

{

Boolean FileOK = false;

if (this.FileUpload1.HasFile)

{

// 限制上传图片小于 2M

if (FileUpload1.PostedFile.ContentLength <= 2097152)

{

// 图片 Guid 重命名

Session["WorkingImage"] = Guid.NewGuid().ToString() + Path.GetExtension(FileUpload1.FileName.ToString()).ToLower();

String FileExtension = Path.GetExtension(Session["WorkingImage"].ToString()).ToLower();

String[] allowedExtensions = { ".png", ".jpeg", ".jpg", ".gif" };

for (int i = 0; i < allowedExtensions.Length; i++)

{

if (FileExtension == allowedExtensions[i])

{

FileOK = true;

}

}

}

// 上传图片大于 2M 警告

else

{

FileOK = false;

Response.Write("<script language=javascript>alert('图片不要超过 2M 大小！');window.location.href=window.location.href;</script>");

}

}

if (FileOK)

{

try

{

//生成原图

Byte[] oFileByte = new byte[this.FileUpload1.PostedFile.ContentLength];

System.IO.Stream oStream = this.FileUpload1.PostedFile.InputStream;

System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);

  

int oWidth = oImage.Width; //原图宽度

int oHeight = oImage.Height; //原图高度

int tWidth; //缩略图宽度

int tHeight; //缩略图高度

  

//按比例计算出缩略图的宽度和高度

if (oWidth >= oHeight)

{

tWidth = 300;

tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));

}

else

{

tHeight = 300;

tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight)));

}

//生成缩略原图

Bitmap tImage = new Bitmap(tWidth, tHeight);

Graphics g = Graphics.FromImage(tImage);

//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(Color.Transparent);

g.DrawImage(oImage, new Rectangle(0, 0, tWidth, tHeight), new Rectangle(0, 0, oWidth, oHeight), GraphicsUnit.Pixel);

  

string fullFileName = this.FileUpload1.PostedFile.FileName.ToString();

fullFileName = fullFileName.Remove(fullFileName.LastIndexOf('.'));

string filename = fullFileName.Substring(fullFileName.LastIndexOf("\\") + 1);

//存储路径

string strLocation = path.ToString();

string tFullName = strLocation + Session["WorkingImage"].ToString();

try

{

// 上传缩略

tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg);

//输出上传成功提示并显示保存路径

TextBox3.Text = "uploadfiles/product/" + Session["WorkingImage"].ToString();

// pic_upload.Visible = false;

// pic_crop.Visible = true;

// 读取缩略图

path = "../uploadfiles/product/" + Session["WorkingImage"].ToString();

  

}

catch (Exception)

{

Response.Write("<script language=javascript>alert('上传失败，请重试！');window.location.href=window.location.href;</script>");

}

finally

{

//释放资源

oImage.Dispose();

g.Dispose();

tImage.Dispose();

}

}

catch (Exception)

{

Response.Write("<script language=javascript>alert('上传失败，请重试！');window.location.href=window.location.href;</script>");

}

}

}