least blurred image

The following script will process a top level directory and write out a .csv file to the desktop with the standard deviation value for each image. The highest Std. Dev. value will be the "sharpest" image.

/* 
least blurred image
https://community.adobe.com/t5/photoshop/least-blurred-image/m-p/12183817

Recursive processing to CSV code based on:
https://forums.adobe.com/message/9697558#9697558

Standard deviation histogram processing code based on:
https://community.adobe.com/t5/photoshop/how-to-get-the-histogram-s-std-dev/td-p/9875041
*/

#target photoshop;
app.bringToFront();

main();

function main() {
    var inputFolder = Folder.selectDialog("Select the folder to process:");
    if (inputFolder === null) return;

    // Add or remove file extensions as required
    var fileList = inputFolder.getFiles(/\.(jpg|dng|tif|psd|crw|cr2|psb|exr|nef|dcr|dc2|erf|raf|orf|tga|mrw|mos|srf|pic|pct|pxr|pdd|pef|png|x3f|rw2)$/i);

    var outputFile = File("~/Desktop/" + decodeURI(inputFolder.name) + ".csv");
    outputFile.open('w');
    outputFile.writeln('Filename,Highest Std. Dev. Value = "Sharpest" Image');

    for (var a in fileList) {

        open(fileList[a]);

        ///////////////////////////////////

        /* 
        How to get the histogram's Std Dev
        https://community.adobe.com/t5/photoshop/how-to-get-the-histogram-s-std-dev/td-p/9875041
        Credit to c.pfaffenbichler for the 2018 code and thanks to Kukurykus for the 2021 update!
        */
        if (app.documents.length > 0 && app.activeDocument.mode == DocumentMode.RGB) {
            var theR = histogramMeanStandardDeviation(app.activeDocument.channels[0].histogram);
            var theG = histogramMeanStandardDeviation(app.activeDocument.channels[1].histogram);
            var theB = histogramMeanStandardDeviation(app.activeDocument.channels[2].histogram);
            var theStdDev = (((theR[2] + theG[2] + theB[2]) / 3).toFixed(2));
            // Write the filename and values
            outputFile.writeln(decodeURI(activeDocument.name) + "," + theStdDev);

        }

        ////// get mean of histogram //////
        function histogramMeanStandardDeviation(theHist) {
            // get total number;
            var thePixels = 0;
            for (var m = 0; m < theHist.length; m++) {
                thePixels = thePixels + theHist[m];
            }

            // get mean and median;
            var theMean = 0;
            var aTotal = 0;
            var check = false;
            for (var n = 0; n < theHist.length; n++) {
                theMean = theMean + (n * theHist[n] / thePixels);
                aTotal = aTotal + theHist[n];
                if (aTotal >= thePixels / 2 && check === false) {
                    theMedian = n;
                    check = true;
                }
            }

            // get standard deviation;
            var theStandDev = 0;
            for (var o = 0; o < theHist.length; o++) {
                theStandDev = theStandDev + (Math.pow((o - theMean), 2) * theHist[o]);
            }
            theStandDev = Math.sqrt(theStandDev / thePixels);
            //
            return ([theMean, theMedian, theStandDev]);
        }

        ///////////////////////////////////

        app.activeDocument.close(SaveOptions.DONOTSAVECHANGES);
    }

    outputFile.close();
    app.beep();
    alert("CSV created:" + "\n" + decodeURI(outputFile));
}