asp.net上传图片自动生成缩略图功能代码-白红宇

asp.net上传图片自动生成缩略图功能代码
阅读量：4957 次
发布时间：2019-06-12
本文共 2964 字，大约阅读时间需要 9 分钟。
              
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>"
); 
} 
} 
}
       
     
转载于:https://www.cnblogs.com/tianxiang2046/archive/2012/05/03/2480644.html
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