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function resizeWithMargin(margin, layer) {
    // Margin in percent from the edge
    // Layer should be centered before resizing
    if (!layer) layer = activeDocument.activeLayer;
    var lyrWidth = layer.bounds[2].value - layer.bounds[0].value;
    var onePercentDoc = activeDocument.width.value / 100;
    var onePercentLyr = lyrWidth / 100;
    var scaly = (onePercentDoc / onePercentLyr) * (100 - (margin * 2));
    layer.resize(scaly, scaly, AnchorPosition.MIDDLECENTER);
}