public class getthumbnail
    inherits system.web.ui.page

#region " web 窗體設(shè)計器生成的代碼 "

    '該調(diào)用是 web 窗體設(shè)計器所必需的。
    <system.diagnostics.debuggerstepthrough()> private sub initializecomponent()

    end sub

    '注意: 以下占位符聲明是 web 窗體設(shè)計器所必需的。
    '不要刪除或移動它。
    private designerplaceholderdeclaration as system.object

    private sub page_init(byval sender as system.object, byval e as system.eventargs) handles mybase.init
        'codegen: 此方法調(diào)用是 web 窗體設(shè)計器所必需的
        '不要使用代碼編輯器修改它。
        initializecomponent()
    end sub

#end region

    private sub page_load(byval sender as system.object, byval e as system.eventargs) handles mybase.load
        '在此處放置初始化頁的用戶代碼
        '獲取幾個參數(shù)，用以生成縮略圖片
        '設(shè)置一個默認(rèn)參數(shù)生成bitmap
        response.clear()
        try
            dim originalfilename as string = server.mappath(request("fn"))
            dim thumbnailwidth as integer = request("tw")
            dim thumbnailheight as integer = request("th")

            dim img as system.drawing.image = system.drawing.image.fromfile(originalfilename)
            dim thisformat as system.drawing.imaging.imageformat = img.rawformat
            dim newsize as system.drawing.size = me.getnewsize(thumbnailwidth, thumbnailheight, img.width, img.height)
            dim outbmp as new system.drawing.bitmap(thumbnailwidth, thumbnailheight)
            dim g as system.drawing.graphics = system.drawing.graphics.fromimage(outbmp)

            '設(shè)置畫布的描繪質(zhì)量
            g.compositingquality = drawing2d.compositingquality.highquality
            g.smoothingmode = drawing2d.smoothingmode.highquality
            g.interpolationmode = drawing2d.interpolationmode.highqualitybicubic
            g.clear(system.drawing.color.fromargb(255, 249, 255, 240))
            g.drawimage(img, new rectangle((thumbnailwidth - newsize.width) / 2, (thumbnailheight - newsize.height) / 2, newsize.width, newsize.height), 0, 0, img.width, img.height, graphicsunit.pixel)
            g.dispose()

            if thisformat.equals(system.drawing.imaging.imageformat.gif) then
                response.contenttype = "image/gif"
            else
                response.contenttype = "image/jpeg"
            end if

            '設(shè)置壓縮質(zhì)量
            dim encoderparams as new system.drawing.imaging.encoderparameters
            dim quality(0) as long
            quality(0) = 100
            dim encoderparam as new system.drawing.imaging.encoderparameter(system.drawing.imaging.encoder.quality, quality)
            encoderparams.param(0) = encoderparam

            '獲得包含有關(guān)內(nèi)置圖像編碼解碼器的信息的imagecodecinfo 對象。
            dim arrayici() as system.drawing.imaging.imagecodecinfo = system.drawing.imaging.imagecodecinfo.getimageencoders()
            dim jpegici as system.drawing.imaging.imagecodecinfo = nothing
            for fwd as integer = 0 to arrayici.length - 1
                if arrayici(fwd).formatdescription.equals("jpeg") then
                    jpegici = arrayici(fwd)
                    exit for
                end if
            next

            if not jpegici is nothing then
                outbmp.save(response.outputstream, jpegici, encoderparams)
            else
                outbmp.save(response.outputstream, thisformat)
            end if
        catch ex as exception

        end try
    end sub

    function getnewsize(byval maxwidth as integer, byval maxheight as integer, byval width as integer, byval height as integer) as system.drawing.size
        dim w as double = 0.0
        dim h as double = 0.0
        dim sw as double = convert.todouble(width)
        dim sh as double = convert.todouble(height)
        dim mw as double = convert.todouble(maxwidth)
        dim mh as double = convert.todouble(maxheight)

        if sw < mw and sh < mh then
            w = sw
            h = sh
        elseif (sw / sh) > (mw / mh) then
            w = maxwidth
            h = (w * sh) / sw
        else
            h = maxheight
            w = (h * sw) / sh
        end if
        return new system.drawing.size(convert.toint32(w), convert.toint32(h))
    end function
end class