Divide layer into 4 quarters and trouble with marquee tool.

Question

Help, please!!! Because I will be doing this often in the near future, I need to create an action to precisely divide a LAYER into 4 quarters, in order to easily create seamless patterns. I'm having trouble figuring out how to automate the placing of guides limited to the center points of the selected layer dimensions, as opposed to the entire image's dimensions. My second difficulty is in selecting the quarters; using the marquee tool, etc, the selection tool is NOT snapping to the guides, despite what I have the Snap To preferences set to. I need to select the pixels right up to the guide line so that I can select the "Make a new layer via cut" and then move the new layers in position to make a seamless tile. Right now, it is selecting a few pixels off. (Annoying!) So until I can figure out how to address these issues, I can't even begin to record an action. Even if I can't record a general action, due to the problem of different layers having different dimensions, I'd be happy to discover a shortcut to accurately quartering a layer and any advice as to why I'm having trouble managing the marquee tool. Maybe I'll get lucky and some kind soul will have already created and be willing to share something to solve this problem I'm currently trying out the CS6 Beta but usually work in either CS5 or PSE 9. For those of you who respond, thanks in advance!

Answer 1

If you want to give a Script a try, paste the following text into a new file in ExtendScript Toolkit (part of Photoshop’s installation, Applications/Utilities/Adobe Utilities/ExtendScript Toolkit CS4 or /Applications/Utilities/Adobe Utilities-CS5/ExtendScript Toolkit CS5) and save it as a jsx-file into Photoshop’s Presets/Scripts-folder.
After restarting Photoshop the Script should be available under File > Scripts and can be assigned a Keyboard Shortcut directly, recorded into an Action, (in CS4 and CS5) be used in a Configurator-Panel or started from ExtendScript Toolkit directly.
// make 4 quadrant copiers of selected layer;
// 2012, use at your own risk;
#target photoshop
if (app.documents.length > 0) {
var myDocument = app.activeDocument;
var originalUnits = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS;
var theLayer = myDocument.activeLayer;
var theBounds = theLayer.bounds;
var theWidth = theBounds[2] - theBounds[0];
var theHeight = theBounds[3] - theBounds[1];
// operation;
var hor = 0;
var ver = 0;
for (var m = 0; m < 4; m++) {
myDocument.activeLayer = theLayer;
// calculate stuff;
var left = theBounds[0] + (theWidth / 2 * hor);
var right = left + (theWidth / 2);
hor++;
if (hor == 2) {hor = 0};
var top = theBounds[1] + (theHeight / 2 * ver);
var bottom = top + (theHeight / 2);
if (String(m / 2).indexOf(".") != -1) {ver++};
// make selection;
var theArray = [[left, top], [right, top], [right, bottom], [left, bottom]];
myDocument.selection.select(theArray, SelectionType.REPLACE, 0, false);
// copy to layer;
var id14 = charIDToTypeID( "CpTL" );
executeAction( id14, undefined, DialogModes.NO );
myDocument.activeLayer.name = theLayer.name + "_" + String(m);
// reset;
app.preferences.rulerUnits = originalUnits;