[PyGerber]: Incorrect rotation angle for polygon

[pgw333]

PyGerber Bug Report

Mandatory checks

Before opening this issue:

• I have reviewed the README for guidelines and haven't found a solution there.
• I have reviewed the PyGerber documentation and haven't found a solution there.
• I have reviewed the existing open issues and verified that this is not a
  duplicate.
• I have reviewed the existing closed issues and verified that this was already
  resolved or marked as won't fix.
• I have reviewed the existing pull requests and verified that this is not a already
  known issue.
• I have reviewed the existing discussions and verified that this is not a already
  known issue.

To Reproduce

Execute command:
pygerber render raster test.txt -o test.png
with file:
test.txt

Expected behavior

The rendering of this Gerber file generates a rectangle rotated 0 degrees, but it should be rotated 45 degrees.

Not correct:

Correct:

Additional context

Environment:

• Operating system: Ubuntu 22.04.5
• Python version: 3.10.12
• PyGerber version: 2.4.3

Optional checks

• I want to contribute example source files attached to this issue in the test suite
  of PyGerber for regression testing purposes.
• I want to include separate LICENSE file for resource files attached as a result of
  an agreement described in first checkbox in this section.
• I want to include separate README file for resource files attached as a result of
  an agreement described in first checkbox in this section.

[newcoder]

Adding an English-language supplement to my earlier Chinese comment. I also filed this as #397, but closed that one as a duplicate of this issue (#396) since the underlying cause appears to be the same.

Summary

This issue is about the Y-axis orientation handling of aperture macros in the SVG backend. Even though a macro may internally contain polygon/circle primitives, the root cause here is in SvgRenderer2Hooks.render_flash_macro() coordinate-system handling.

Minimal reproduction file

Generate the following file gerber_shape_test.gbr with gerber_writer:

from gerber_writer import Circle, DataLayer, RoundedRectangle

top = DataLayer("Copper,L1,Top,Signal")
top.add_pad(
    RoundedRectangle(1.257, 2.286, 0.254, "SMDPad,CuDef"),
    (0, 2.54),
    angle=45,
)
with open("gerber_shape_test.gbr", "w") as f:
    top.dump_gerber(f)

The resulting Gerber contains a RoundedRectangle macro aperture with width 1.257, height 2.286, corner radius 0.254, rotated by 45°.

Reproduction code

from pygerber.gerberx3.api.v2 import GerberFile

parsed = GerberFile.from_file("gerber_shape_test.gbr").parse()
parsed.render_svg("output.svg")
parsed.render_raster("output.png")

Actual vs expected behavior

• PNG (raster): long axis runs from top-left to bottom-right, matching the original macro geometry.
• SVG (before fix): long axis runs from bottom-left to top-right, i.e. the shape looks rotated by ~90°.
• Expected: SVG output should be identical to PNG/BMP output.

Root cause

File: src/pygerber/gerberx3/renderer2/svg.py

SvgRenderer2Hooks.render_flash_macro() caches the macro aperture group with flip_y=False:

self.push_render_frame(
    command.get_bounding_box(),
    normalize_origin_to_0_0=False,
    flip_y=False,  # <-- problem
)

This leaves the macro group in the Gerber Y-up coordinate system, while the rest of the SVG canvas uses Y-down. Placing this Y-up <g> into the Y-down SVG via <use> produces a vertical mirror of the macro geometry. The mismatch is invisible for mirror-symmetric shapes (squares, circles) but appears as a 90° rotation for rotated non-symmetric shapes such as the RoundedRectangle above.

Proposed fix

Wrap the cached macro group with transform="scale(1,-1)" so its local Y axis matches the SVG canvas:

frame = self.pop_render_frame()
aperture_group = drawsvg.Group(
    [frame.group],
    transform="scale(1,-1)",
)
self.set_aperture(aperture_id, aperture_group)

Verification

After applying the fix:

• output.svg and output.png have the same long-axis orientation.
• Verified with pygerber 2.4.3, Python 3.13, Windows 11.

Environment

• PyGerber version: 2.4.3
• Python version: 3.13
• OS: Windows 11

[Argmaster]

Hi,
Thanks for putting in the effort and delivering a high quality bug report!
In general 2.4.3 is huge can of worms when it comes to handling anything beyond basic set of features of Gerber, which is unfortunate flaw in its design.
However, most of its shortcomings have been addressed in version 3.0.0 prototype.
Please try rendering it with PyGerber 3.0.0a4 and confirm if it works for your needs.
This and many other, more complicated nested rotations should work fine there.

pip install pygerber==3.0.0a4
pygerber gerber convert jpeg file.txt

[pgw333]

I've tested it with PyGerber 3.0.0a4 and it works correctly. Thank you.