How to check if a layer contains any transparent pixels?

[奋飞曾20888973]

I want to export layers to image files(png, jpg). To export smaller image files, I want to export layers with transparent pixels to PNG file, and layers without any transparent pixels to JPG files. I think I need to get the color of every pixel of the layer, then check if any of the color contains transparency. So how can I do this with
ExtendScript? I checked the API reference and google a lot, but didn't find a solution.

[Tom Winkelmann]

You can take this thread as start...

checking each individual pixel of a layer for transparency

[r-bin · Accepted solution]

alert("Layer " + (layer_is_solid()?"does not have ":"has a ") + "transparency")
function layer_is_solid()
    {
    try {
        var solid = false;
        selection_from_layer();
        try { app.activeDocument.selection.feather(0); } catch(e) { solid = true; }
        app.activeDocument.selection.deselect(); 
        return solid;
        }
    catch(e) { alert(e); throw(e); }
    }
function selection_from_layer()
    {
    try {
        var r1 = new ActionReference();
        r1.putProperty(charIDToTypeID("Chnl"), charIDToTypeID("fsel"));
        var d = new ActionDescriptor();
        d.putReference(charIDToTypeID("null"), r1);
        var r2 = new ActionReference();
        r2.putEnumerated(charIDToTypeID("Chnl"), charIDToTypeID("Chnl"), charIDToTypeID("Trsp"));
        d.putReference(charIDToTypeID("T   "), r2);
        executeAction(charIDToTypeID("setd"), d, DialogModes.NO);
        }
    catch(e) { throw(e); }
    }

[nickcombs]

Interesting workaround. For me, it gives false on an empty layer and true on layers with any non-transparent pixels. But I'm looking for a way to flag any layer that isn't completely solid.

[nickcombs]

Here is the modification that works for me. I added the invert_selection_from_layer function and some displayDialogs managment. 

// https://community.adobe.com/t5/photoshop-ecosystem-discussions/how-to-check-if-a-layer-contains-any-transparent-pixels/td-p/9917339



alert("Layer " + (layer_is_solid() ? "does not have " : "has a ") + "transparency")



function layer_is_solid()
{
  try {
    displayDialogs = DialogModes.NO
    var solid = false;
    selection_from_layer();
    invert_selection_from_layer();
    try {
      app.activeDocument.selection.feather(0);
    } catch (e) {
      solid = true;
    }
    app.activeDocument.selection.deselect();
    displayDialogs = DialogModes.ERROR
    return solid;
  } catch (e) {
    displayDialogs = DialogModes.ERROR
    alert(e);
    throw (e);
  }
} // layer_is_solid



function selection_from_layer()
{
  try {
    var r1 = new ActionReference();
    r1.putProperty(charIDToTypeID("Chnl"), charIDToTypeID("fsel"));
    var d = new ActionDescriptor();
    d.putReference(charIDToTypeID("null"), r1);
    var r2 = new ActionReference();
    r2.putEnumerated(charIDToTypeID("Chnl"), charIDToTypeID("Chnl"), charIDToTypeID("Trsp"));
    d.putReference(charIDToTypeID("T   "), r2);
    executeAction(charIDToTypeID("setd"), d, DialogModes.NO);
  } catch (e) {
    throw (e);
  }
} // selection_from_layer


function invert_selection_from_layer() {
  try {
    executeAction( charIDToTypeID( "Invs" ), undefined, DialogModes.NO );
  } catch (e) {
    throw (e);
  }
} // invert_selection_from_layer

[Stephen_A_Marsh]

@nickcombs thanks for contributing... For me, your code is still flagging a single transparent layer with no content as not having transparency.

[nickcombs · Accepted solution]

Thanks for catching that @Stephen_A_Marsh. I have updated the code below with a layer_is_empty function to handle that special case.

// https://community.adobe.com/t5/photoshop-ecosystem-discussions/how-to-check-if-a-layer-contains-any-transparent-pixels/td-p/9917339



alert( "Layer is " +( layer_is_solid() ? "solid" : "transparent" ) )



function layer_is_solid() {
  try {
    displayDialogs = DialogModes.NO
    var solid = false
    var doc = app.activeDocument
    selection_from_layer()
    invert_selection_from_layer()
    try { doc.selection.feather(0) }
    catch (e) { solid = true }
    if( layer_is_empty( doc.activeLayer) ) solid = false
    doc.selection.deselect()
    displayDialogs = DialogModes.ERROR
    return solid
  } catch (e) {
    displayDialogs = DialogModes.ERROR
    throw ( 'layer_is_solid >> '+ e )
  }
} // layer_is_solid



function selection_from_layer() {
  try {
    var r1 = new ActionReference()
    r1.putProperty( chID("Chnl"), chID("fsel") )
    var d = new ActionDescriptor()
    d.putReference( chID("null"), r1 )
    var r2 = new ActionReference()
    r2.putEnumerated( chID("Chnl"), chID("Chnl"), chID("Trsp") )
    d.putReference( chID("T   "), r2 )
    executeAction( chID("setd"), d, DialogModes.NO )
  } catch (e) {
    throw ( 'selection_from_layer >> '+ e )
  }
} // selection_from_layer



function invert_selection_from_layer() {
  try {
    executeAction( chID( "Invs" ), undefined, DialogModes.NO )
  } catch (e) {
    throw ( 'invert_selection_from_layer >> '+ e )
  }
} // invert_selection_from_layer



function layer_is_empty( artLayer ) {
  try {
    var bds = artLayer.bounds
    if( bds[0].value || bds[1].value || bds[2].value || bds[3].value )
      return false
    return true
  } catch (e) {
    throw ( 'layer_is_empty >> '+ e )
  }
} // layer_is_empty



function chID( a ) { return charIDToTypeID( a )}