checking each individual pixel of a layer for transparency

[Fedtke]

hi,

i'm very confused and challenged in understanding on how a photoshop script can

access step-by-step each indidual pixel of a given layer in order to check it's

transparency. means, I need to identify transparent pixels.

I especially need to check whether/which pixels are transparent. isn't this transparency coded

in the alpha value of a pixel? I have transparent pixels in my PSD file layer, but there is no

alpha channel displayed in photoshop, only the three R, G and B layers. how can this work?

thanks for any help.

best

stephen

[Paul Riggott · Accepted solution]

Testing each pixel would take forever.

You can do this though...

#target photoshop
main();
function main(){
selectTransparency();
try{ 
var sBnds = app.activeDocument.selection.bounds;
    }catch(e){
        alert("This layer does not have transparency");
        return;
        }
alert("Transparent pixels have been selected");
}
function selectTransparency() {
    var desc52 = new ActionDescriptor();
        var ref47 = new ActionReference();
        ref47.putProperty( charIDToTypeID('Chnl'), charIDToTypeID('fsel') );
    desc52.putReference( charIDToTypeID('null'), ref47 );
        var ref48 = new ActionReference();
        ref48.putEnumerated( charIDToTypeID('Chnl'), charIDToTypeID('Chnl'), charIDToTypeID('Trsp') );
    desc52.putReference( charIDToTypeID('T   '), ref48 );
    desc52.putBoolean( charIDToTypeID('Invr'), true );
    try{
    executeAction( charIDToTypeID('setd'), desc52, DialogModes.NO );
    }catch(e){}
};

This would be the same as :-

Selection - Load selection - Layer # Transparency with Invert selected.