property |NSURL| : a reference to current application’s |NSURL|
property NSUUID : a reference to current application’s NSUUID
property NSArray : a reference to current application’s NSArray
property NSString : a reference to current application’s NSString
property NSImage : a reference to current application’s NSImage
property NSPredicate : a reference to current application’s NSPredicate
property NSJPEGFileType : a reference to current application’s NSJPEGFileType
property NSBitmapImageRep : a reference to current application’s NSBitmapImageRep
property NSURLTypeIdentifierKey : a reference to current application’s NSURLTypeIdentifierKey

property compressList : {100, 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 40, 30, 20, 25} –大→小　へと並んでいる必要がある
property kbBase : 1024

tell application "Finder"
　　set inFiles to selection as alias list
end tell

–指定のAlias listのうち画像ファイルのみ抽出
set filRes1 to filterAliasListByUTI(inFiles, "public.image") of me
if filRes1 = {} then return

–ターゲットサイズを指定
set aMessage to "Input Target size in KB ( " & (kbBase as string) & " based )"
set aRes to text returned of (display dialog aMessage default answer "300" buttons {"OK"} default button 1)
if aRes = false or aRes = "" then return
set targLimit to (aRes as number) * kbBase

–選択中のファイルのうちの１つから親フォルダを求め、出力先ファイルパスを組み立てる
set outPathTarg to (contents of first item of filRes1)
set pathString to NSString’s stringWithString:outPathTarg
set newPath to (pathString’s stringByDeletingLastPathComponent()) as string

–Main Loop
repeat with i in filRes1
　　set aNSImage to (NSImage’s alloc()’s initWithContentsOfFile:(i))
　　
　　–巨大すぎる画像のリサイズ時への保険で、最小サイズで投機的に圧縮して結果を確認する
　　set minSize to calcSavedJPEGSizeFromNSIMage(aNSImage, (last item of compressList) / 100) of me
　　
　　if minSize < targLimit then
　　　　–Simulate Suitable JPEG Compression Ratio to target file size
　　　　repeat with ii in compressList
　　　　　　set jj to ii / 100
　　　　　　set fileSize to calcSavedJPEGSizeFromNSIMage(aNSImage, jj) of me
　　　　　　
　　　　　　if fileSize < targLimit then
　　　　　　　　exit repeat
　　　　　　end if
　　　　end repeat
　　else
　　　　set jj to 0.01 –エラー時にはやけくそで1%まで圧縮指定
　　end if
　　
　　set outPOSIXpath to (newPath & "/" & (NSUUID’s UUID()’s UUIDString()) as string) & "_" & (jj as string)
　　set savePath to outPOSIXpath & ".jpg"
　　
　　saveNSImageAtPathAsJPG(aNSImage, savePath, jj) of me
end repeat

–Alias listから指定UTIに含まれるものをPOSIX pathのリストで返す
on filterAliasListByUTI(aList, targUTI)
　　set newList to {}
　　repeat with i in aList
　　　　set j to POSIX path of i
　　　　set tmpUTI to my retUTIfromPath(j)
　　　　set utiRes to my filterUTIList({tmpUTI}, targUTI)
　　　　if utiRes is not equal to {} then
　　　　　　set the end of newList to j
　　　　end if
　　end repeat
　　return newList
end filterAliasListByUTI

–指定のPOSIX pathのファイルのUTIを求める
on retUTIfromPath(aPOSIXPath)
　　set aURL to |NSURL|’s fileURLWithPath:aPOSIXPath
　　set {theResult, theValue} to aURL’s getResourceValue:(reference) forKey:NSURLTypeIdentifierKey |error|:(missing value)
　　
　　if theResult = true then
　　　　return theValue as string
　　else
　　　　return theResult
　　end if
end retUTIfromPath

–UTIリストが指定UTIに含まれているかどうか演算を行う
on filterUTIList(aUTIList, aUTIstr)
　　set anArray to NSArray’s arrayWithArray:aUTIList
　　set aPred to NSPredicate’s predicateWithFormat_("SELF UTI-CONFORMS-TO %@", aUTIstr)
　　set bRes to (anArray’s filteredArrayUsingPredicate:aPred) as list
　　return bRes
end filterUTIList

–NSImageを指定パスにJPEG形式で保存、qulityNumは0.0〜1.0。1.0は無圧縮
on saveNSImageAtPathAsJPG(anImage, outPath, qulityNum as real)
　　set imageRep to anImage’s TIFFRepresentation()
　　set aRawimg to NSBitmapImageRep’s imageRepWithData:imageRep
　　set pathString to NSString’s stringWithString:outPath
　　set newPath to pathString’s stringByExpandingTildeInPath()
　　set myNewImageData to (aRawimg’s representationUsingType:(NSJPEGFileType) |properties|:{NSImageCompressionFactor:qulityNum})
　　
　　set aLength to (myNewImageData’s |length|()) as number
　　
　　set aRes to (myNewImageData’s writeToFile:newPath atomically:true) as boolean
　　return aRes –true/false
end saveNSImageAtPathAsJPG

–NSImageをJPEG形式で保存したときのファイルサイズを計算
on calcSavedJPEGSizeFromNSIMage(anImage, qulityNum as real)
　　set imageRep to anImage’s TIFFRepresentation()
　　set aRawimg to NSBitmapImageRep’s imageRepWithData:imageRep
　　set myNewImageData to (aRawimg’s representationUsingType:(NSJPEGFileType) |properties|:{NSImageCompressionFactor:qulityNum})
　　set aLength to (myNewImageData’s |length|()) as number
　　return aLength
end calcSavedJPEGSizeFromNSIMage