Detect if canvas is empty, problem with white image.

[Jake7732]

I have compiled a script that detects if a given file is completely blank and if it is it creates a 2px x 2px black box and then trims down to it.

The issue i am having is if a file is entirely white (like a white box on a transparent canvas) the script thinks the file is empty and creates a 2px x 2px box.

Cant figure out how to make the histogram understand white, though through my understanding of histogram is it sees it as a black/white image?

#target photoshop  
var doc = activeDocument  
app.preferences.rulerUnits = Units.PIXELS;  
var tally = 0;  
var empty = false;  
for(var j=0;j<doc.channels.length;j++)
{  
    var h = doc.channels.histogram;  
    for (i=0;i<h.length;i++){  
        if(h == parseInt(doc.width*doc.height))
        {
             empty = true
               var boxFill = new SolidColor();
               boxFill.rgb.red = 0;
               boxFill.rgb.green = 0;
               boxFill.rgb.blue = 0;
               var selectionPX = [
                    [0,0],
                    [0,2],
                    [2,2],
                    [2,0]
               ]
               doc.selection.select(selectionPX);
               doc.selection.fill (boxFill);
               doc.selection.deselect ();
         }  
    }  
    if(empty)
    {
       tally++;
    }  
    empty = false;  
}   
    if (tally!=doc.channels.length)
    {
    doc.trim(TrimType.TRANSPARENT)
};  

[r-bin · Accepted solution]

Blank - does this mean completely transparent?
If yes, then try.

var blank = true;  
var d = new ActionDescriptor();  
var r = new ActionReference();  
r.putProperty(stringIDToTypeID("channel"), stringIDToTypeID("selection"));  
d.putReference(stringIDToTypeID("null"), r);  
var r1 = new ActionReference();  
r1.putEnumerated(stringIDToTypeID("channel"), stringIDToTypeID("channel"), stringIDToTypeID("transparencyEnum"));  
r1.putEnumerated(stringIDToTypeID("layer"), stringIDToTypeID("ordinal"), stringIDToTypeID("merged")); 
d.putReference(stringIDToTypeID("to"), r1);  
try { executeAction(stringIDToTypeID("set"), d, DialogModes.NO); }  catch(e) { blank = false; }  
if (blank) try { app.activeDocument.selection.bounds; blank = false; } catch (e) { }  
app.activeDocument.selection.deselect();
alert(blank);

[Jake7732]

That works!

Curious to learn more about what ActionDescriptor and ActionReference with putProperty/putReference, Any good links you could recommend?

Thanks!