photoshop-createBleed1cm_Layer Flipping Works in Photoshop Scripting

How Layer Flipping Works in Photoshop Scripting

• Horizontal Flip: layer.resize(-100, 100, AnchorPosition.MIDDLECENTER)

• Vertical Flip: layer.resize(100, -100, AnchorPosition.MIDDLECENTER)

• Both (180° / Corner Flip): layer.resize(-100, -100, AnchorPosition.MIDDLECENTER)

#target photoshop

function createMirrorBleed() {
    if (!app.documents.length) return;
    
    var doc = app.activeDocument;
    var origUnits = app.preferences.rulerUnits;
    app.preferences.rulerUnits = Units.PIXELS; // Use Pixels for exact boundary alignment

    doc.suspendHistory("4-Side Mirror Bleed", "runMirrorDOM()");

    app.preferences.rulerUnits = origUnits;
}

function runMirrorDOM() {
    var doc = app.activeDocument;

    // 1. Flatten to establish a single base source
    if (doc.layers.length > 1) doc.flatten();
    var origLayer = doc.activeLayer;
    if (origLayer.isBackgroundLayer) origLayer.isBackgroundLayer = false;

    // Calculate 1cm bleed equivalent in pixels based on document DPI
    var bleedPx = Math.round((doc.resolution / 2.54) * 1); // 1 cm in pixels
    var w = doc.width.value;
    var h = doc.height.value;

    // 2. Expand Canvas
    doc.resizeCanvas(w + (bleedPx * 2), h + (bleedPx * 2), AnchorPosition.MIDDLECENTER);

    // Helper: Create mirrored layer edge via duplication & crop/position
    function makeEdge(x1, y1, x2, y2, flipH, flipV, transX, transY) {
        doc.activeLayer = origLayer;
        doc.selection.select([[x1, y1], [x2, y1], [x2, y2], [x1, y2]]);
        
        // Copy selection via clipboard to bypass ActionManager
        doc.selection.copy();
        var newL = doc.paste();
        doc.selection.deselect();

        if (flipH) newL.flip(Direction.HORIZONTAL);
        if (flipV) newL.flip(Direction.VERTICAL);

        newL.translate(transX, transY);
        return newL;
    }


function makeEdge(x1, y1, x2, y2, flipH, flipV, transX, transY) {
    doc.activeLayer = origLayer;
    doc.selection.select([[x1, y1], [x2, y1], [x2, y2], [x1, y2]]);
    
    // Copy selection to new layer
    doc.selection.copy();
    var newL = doc.paste();
    doc.selection.deselect();

    // Use negative scaling percentages to flip the layer
    var scaleX = flipH ? -100 : 100;
    var scaleY = flipV ? -100 : 100;

    if (flipH || flipV) {
        newL.resize(scaleX, scaleY, AnchorPosition.MIDDLECENTER);
    }

    // Position the mirrored piece
    newL.translate(transX, transY);
    return newL;
}

    // Coordinates relative to resized canvas (centered original sits at offset bleedPx)
    var xL = bleedPx;
    var xR = bleedPx + w;
    var yT = bleedPx;
    var yB = bleedPx + h;

    // 3. Generate Edges
    var topL   = makeEdge(xL, yT, xR, yT + bleedPx, false, true, 0, -bleedPx);
    var botL   = makeEdge(xL, yB - bleedPx, xR, yB, false, true, 0, bleedPx);
    var leftL  = makeEdge(xL, yT, xL + bleedPx, yB, true, false, -bleedPx, 0);
    var rightL = makeEdge(xR - bleedPx, yT, xR, yB, true, false, bleedPx, 0);

    // 4. Generate Corners
    makeEdge(xL, yT, xL + bleedPx, yT + bleedPx, true, true, -bleedPx, -bleedPx);
    makeEdge(xR - bleedPx, yT, xR, yT + bleedPx, true, true, bleedPx, -bleedPx);
    makeEdge(xL, yB - bleedPx, xL + bleedPx, yB, true, true, -bleedPx, bleedPx);
    makeEdge(xR - bleedPx, yB - bleedPx, xR, yB, true, true, bleedPx, bleedPx);

    // 5. Re-order main artwork layer to top
    origLayer.move(topL, ElementPlacement.PLACEBEFORE);
}

createMirrorBleed();