Restore @theomega invert_axis

Author: tatarize

vpype_gcode/gwrite.py

@@ -6,9 +6,41 @@
 import vpype as vp
 
 # Load the default config
+from vpype import LayerType
+
 vp.CONFIG_MANAGER.load_config_file(str(Path(__file__).parent / "bundled_configs.toml"))
 
 
+def invert_axis(
+    document: vp.Document,
+    invert_x: bool,
+    invert_y: bool
+):
+    """ Inverts none, one or borth axis of the document.
+    This applies a relative scale operation with factors of 1 or -1
+    on the two axis to all layers. The invertion happens relative to
+    the center of the bounds.
+    """
+
+    layer_ids = vp.multiple_to_layer_ids(LayerType.ALL, document)
+    bounds = document.bounds(layer_ids)
+
+    if not bounds:
+        return document
+
+    origin = (
+        0.5 * (bounds[0] + bounds[2]),
+        0.5 * (bounds[1] + bounds[3]),
+    )
+
+    for vid in layer_ids:
+        lc = document[vid]
+        lc.translate(-origin[0], -origin[1])
+        lc.scale(-1 if invert_x else 1, -1 if invert_y else 1)
+        lc.translate(origin[0], origin[1])
+
+    return document
+
 @click.command()
 @click.argument("output", type=click.File("w"))
 @click.option(