Script or Action to Batch Determine Transparency?

There are many possibilities using an ExifTool conditional based around transparency. Command line code examples for the Mac OS follows (Windows users would simply swap around the double/single straight quotes and use appropriate file paths). As these commands overwrite the original files without making any backups, work on copies and or use at your own risk.

To recursively move files matching the if condition to a new folder titled Transparent Images in all sub folders under the top-level input folder on the desktop of the user Bob:

exiftool -overwrite_original -r -if '$AlphaChannelsNames eq "Transparency"' -directory=%d'Transparent Images' '/Users/bob/Desktop/top level input folder'

Alternatively, to recursively apply metadata such as a Bridge label of Review in all folders/files under the top-level input folder on the desktop of the user Bob:

exiftool -overwrite_original -r -if '$AlphaChannelsNames eq "Transparency"' -label='Review' '/Users/bob/Desktop/top level input folder'

Or to recursively apply metadata such as a Bridge rating of five stars in all folders/files under the top-level input folder on the desktop of the user Bob:

exiftool -overwrite_original -r -if '$AlphaChannelsNames eq "Transparency"' -rating='5' '/Users/bob/Desktop/top level input folder'

You could try script for Bridge. It does not open document and it read image pixels.

$.hiresTimer
#target bridge  
$.memCache = 20000000;
$.gc();
var fle = new File(Folder.desktop + '/sample-file.psd' );
reading(new BitmapData(fle, true))  
  
function reading(v) {  
height = v.height;
width = v.width;
j = 0;
i = 0;
r = new Array(height);
c = new Array(width);
     for(; j < height; j++) { 
          for(i=0; i < width; i++) {  
               c = new Color(v.getPixel(i, j)).toString(); 
          }  
//c = (' '+c.toString());
r = c.slice();
if(j==1){
if(r[0]===r[1]){
alert("same");
}
}
     }  
     var txt = File(fle.toString().slice(0, -3) + 'txt');
txt.open('w');  
     txt.write(r.toSource()); 
txt.close()  
} 
$.writeln($.hiresTimer/1000 + " ms");

This reads sample-file.psd inside desktop folder and saves data as .txt file. So you would modify input/output files.

Data are in #AARRGGBB format so you need only first two numbers.

I strongly recommend stop "for" loop when you find first transparent pixel and check next image.

Not opening the file is unlikely to succeed. If you open it, you can use a script to determine if there is transparency.

var transp = true;
var d = new ActionDescriptor();
var r = new ActionReference();
r.putProperty( charIDToTypeID( "Chnl" ), charIDToTypeID( "fsel" ) );
d.putReference( charIDToTypeID( "null" ), r );
var r2 = new ActionReference();
r2.putEnumerated( charIDToTypeID( "Chnl" ), charIDToTypeID( "Chnl" ), charIDToTypeID( "Trsp" ) );
r2.putEnumerated( charIDToTypeID( "Lyr " ), charIDToTypeID( "Ordn" ), charIDToTypeID( "Mrgd" ) ); 
d.putReference( charIDToTypeID( "T   " ), r2 );
try { 
    executeAction( charIDToTypeID( "setd" ), d, DialogModes.NO ); 
    activeDocument.selection.invert();
    try { activeDocument.selection.bounds; } catch(e) { transp = false; }
    } 
catch(e) { transp = false; }
activeDocument.selection.deselect();
if (transp) alert("Has transparency");
else        alert("No transparency");

If you saved PSD with maximum compatibility then you can hold left Alt + Shift and you can load composite data instead layers. This will open file much much faster. But it seems to be wired with keys and I don't know how to script it. So you could use brick as workaround :-D

In channels class is Alpha Channel for transparent pixels. It has index -1 in action reference. But values doesn't makes sense to me.

Alternatively you can load layer transparency into selection, then switch into quick mask mode and read histogram for quick mask channels. It shows me correct values.

Or there is possibility to build PSD binary parser. Composite data are last block in PSD: Adobe Photoshop File Formats Specification

This is fastest solution because you read only data you need and you don't need open PSD file. But it is most difficult.

Moving to Photoshop Scripting​

You may want to do a search over at

Photoshop Scripting