How to change a layers opacity?

[caillte]

Hi there,

I am new to the whole concept of photoshop cripting and am really struggling,  I wish to change the opacity of several layers, do I have to define the function first??

I would really appreciate it if someone could help!! realy struggling here

[Michael_L_Hale]

The opacity of a layer is changed by setting the layer object's opacity property

app.activeDocument.activeLayer.opacity = 50;

You can only set the opacity one layer at a time so if you want to change several layers you will need to change them one at a time.

You do not have to have a function or other control structures like a loop but depending on what else you want to do or coding style them could be helpful.

[caillte]

so I just have it in the wrong place? sorry.. im really stuck here  

                    app.activeDocument=doc1;

                    doc1.resizeImage(posterWidth,posterHeight/4);

                    doc1.selection.selectAll();

                    doc1.selection.copy();

                    doc1.selection.deselect();

                    app.activeDocument=newDoc;

                    newDoc.artLayers.add();

                    newDoc.paste();

                    newDoc.activeLayer.translate(0,-posterHeight/2+posterHeight/8);

                    app.activeDocument=newDoc;

                    newDoc.selection.selectAll();

                    newDoc.selection.opacity = 17;

                    newDoc.selection.deselect();

[pixxxelschubser]

Not yet the correct syntax.

Try something like this (look to compare):

var doc1 = app.activeDocument;
var h = doc1.height ;
var w = doc1.width;
doc1.resizeImage (w, h/4);
doc1.selection.selectAll();
doc1.selection.copy();
doc1.selection.deselect(); // do never save your doc1 at this time !!!
var newDoc = app.documents.add ();
newDoc.paste();
newDoc.activeLayer.translate (0, -h/2+h/8);
newDoc.activeLayer.opacity = 17;
app.refresh();

[Michael_L_Hale]

You want to change a layer's opacity. You do that by changing the layer's opacity property. Your code tries to change a selection property. Because selection does not have an opacity property what that line really does is create a new property for selection and sets it to 17. There is no error but it doesn't do what you want.

If you are just starting you may want to look at the Photoshop JavaScript Reference for you version of Photoshop. It lists the object, properties, and methods for Photoshop.