#target photoshop
app.bringToFront();

var PRESOLUTION = 72;

main();

function main() {    
    var l = 800;
    l=prompt("请输入图片宽高的像素最大值：", "800");
    if(l==null){ return false; }
    if(!isInt(l)){
        alert("输入值只能是大于 0 的整数！");
        return false;
        }
    var topFolder = Folder.selectDialog("选择待处理文件夹", "~");
    var  fileList=new Array();
    fileList=FindAllFiles(topFolder.toString(), /\.(jpg|tif|psd|bmp|gif|png)$/i, fileList);
    for (var a=0; a<fileList.length; a++){
        open (fileList[a]);
        var oldPref = app.preferences.rulerUnits;
        app.preferences.rulerUnits = Units.PIXELS;
        var doc = app.activeDocument;
        var w = doc.width;
        var h = doc.height;        
        if(h > l || w > l) { //图片高或宽大于设定值才会处理
            if (h > w){ //竖式图片
                w =Math.round( w * l / h);
                h = l;
             }else{ //横式或正方形图片
                 h = Math.round( h * l / w);
                 w = l;
                 }                    
             //alert(w + "," + h);
             doc.resizeImage(UnitValue(w,'px'),UnitValue(h,'px'));
             app.preferences.rulerUnits = oldPref;
             doc.close(SaveOptions.SAVECHANGES);
             }
         }
    }

function isInt(v){
    return ((Math.round(v) == v) && v > 0);
    }

///////////////////////////////////////////////////////////////////////////////
// Function: FindAllFiles
// Usage: Find all the files in the given folder recursively
// Input: srcFolder is a string to a folder
//          destArray is an Array of File objects
// Return: Array of File objects, same as destArray
///////////////////////////////////////////////////////////////////////////////
function FindAllFiles( srcFolderStr, mask, destArray ) {
    var fileFolderArray = Folder( srcFolderStr ).getFiles();
    for ( var i = 0; i < fileFolderArray.length; i++ ) {
        var fileFoldObj = fileFolderArray[i];
        if ( fileFoldObj instanceof File ) {
            if (fileFoldObj.fullName.search(mask) ) { destArray.push( fileFoldObj ); }
        } else { // folder
            FindAllFiles( fileFoldObj.toString(), mask, destArray );
        }
    }
    return destArray;
}