制作最清晰缩略图的完整类(VB.NET版)

先收集一些相关资源

Public Class ClassUpPic

    Private vPicFile As System.Web.UI.HtmlControls.HtmlInputFile

    Private vSmallPicSize, vUpFileSize As Integer

    Private vUpPicPath, vNewPicName, vTmpPicName As String

    Private PicMin, PicMax, vPicMax As System.Drawing.Image

    Private PicFormat As System.Drawing.Imaging.ImageFormat

    Private MinHeight, MinWidth As Decimal

    Private Myfile As IO.File

    Public Sub New(ByVal PicFile As System.Web.UI.HtmlControls.HtmlInputFile, ByVal UpPicType As PicType)

        vPicFile = PicFile

        vUpFileSize = HttpContext.Current.Application("UpFileSize")

        Select Case UpPicType

            Case PicType.Face

                vUpPicPath = "upload/images/Face"

                vSmallPicSize = 150

                vNewPicName = HttpContext.Current.Session("MemberID") & "." & GetRightByChar(vPicFile.PostedFile.FileName, ".")

            Case PicType.Photo

                vUpPicPath = "upload/images/Photo"

                vSmallPicSize = 150

                vNewPicName = System.Guid.NewGuid.ToString() & "." & GetRightByChar(vPicFile.PostedFile.FileName, ".")

            Case PicType.Pic

                vUpPicPath = "upload/images/Pic"

                vSmallPicSize = 550

                vNewPicName = System.Guid.NewGuid.ToString() & "." & GetRightByChar(vPicFile.PostedFile.FileName, ".")

        End Select

    End Sub

    Public Function GetSavedFileName() As String

        '检验图片类型=================================================================

        If vPicFile.PostedFile.FileName = "" Then

            Throw New NotSupportedException("文件为空，请您选择上传的图片文件！")

        End If

        If Left(vPicFile.PostedFile.ContentType, 5) <> "image" Then

            Throw New NotSupportedException("文件格式不合法，请选取有效的图片文件！" & vPicFile.PostedFile.ContentType)

        End If

        If vPicFile.PostedFile.ContentLength > vUpFileSize Then

            Dim MaxNumber As Decimal = vUpFileSize / 1024 / 1024

            Throw New NotSupportedException("上传的图片文件太大,最大支持" & Format(MaxNumber, "##,##0") & "M！")

        End If

        '检验数量限制=================================================================

        '保存大文件=================================================================

        vPicFile.PostedFile.SaveAs(HttpContext.Current.Server.MapPath(vUpPicPath & "/max/") & vNewPicName)

        vPicFile.Dispose()

        '缩略图片文件=================================================================

        PicMax = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(vUpPicPath & "/max/") & vNewPicName)

        If Not (PicMax.RawFormat Is PicFormat.Gif Or PicMax.RawFormat Is PicFormat.Png) Then

            If PicMax.Height > vSmallPicSize Or PicMax.Width > vSmallPicSize Then

                vTmpPicName = System.Guid.NewGuid.ToString() & ".png"

                vPicMax = PicMax

                PicMax.Save(HttpContext.Current.Server.MapPath(vUpPicPath & "/max/") & vTmpPicName, PicFormat.Png)

                vPicMax.Dispose()

                PicMax = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(vUpPicPath & "/max/") & vTmpPicName)

            End If

        End If

        '保存小文件=================================================================

        GetMinPic(PicMax).Save(HttpContext.Current.Server.MapPath(vUpPicPath & "/min/") & vNewPicName, PicFormat.Jpeg)

        PicMax.Dispose()

        '删除临时png文件=================================================================

        If vTmpPicName <> "" Then Myfile.Delete(HttpContext.Current.Server.MapPath(vUpPicPath & "/max/") & vTmpPicName)

        Return vNewPicName

    End Function

    Private Function GetMinPic(ByVal MaxPic As System.Drawing.Image) As System.Drawing.Image

        If MaxPic.Height > vSmallPicSize Or MaxPic.Width > vSmallPicSize Then

            If MaxPic.Height > MaxPic.Width Then

                MinWidth = MaxPic.Width / (MaxPic.Height / vSmallPicSize)

                MinHeight = vSmallPicSize

            Else

                MinWidth = vSmallPicSize

                MinHeight = MaxPic.Height / (MaxPic.Width / vSmallPicSize)

            End If

            Return MaxPic.GetThumbnailImage(CInt(MinWidth), CInt(MinHeight), Nothing, New System.IntPtr())

        Else

            Return MaxPic

        End If

    End Function

    Enum PicType

        Face = 1

        Photo = 2

        Pic = 3

    End Enum

    Private Function GetRightByChar(ByVal StrValue As String, ByVal CharValue As String) As String

        Dim MyStr() As String = Split(StrValue, CharValue)

        Return MyStr(MyStr.Length - 1)

    End Function

End Class

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