feat(tt_tool): scramble stdcell layers in png render for IHP & GF (#129)

* feat(tt_tool): scramble stdcell layers in png render for IHP & GF

* fix(tt_tool): resolve mypy errors

* refactor(tt_tool): separate svg & png rendering into render_utils.py

render_utils.py

@@ -0,0 +1,147 @@
+import logging
+import os
+import random
+import re
+import subprocess
+
+import cairosvg  # type: ignore
+import gdstk  # type: ignore
+
+
+# Custom exception for convert_svg_to_png()
+class SVGTooComplexError(Exception):
+    pass
+
+
+# Helper function to randomize layer order of polygons in a subcell in a deterministic way
+def scramble_polygons(polygons, seed):
+    # group polygons by layer/datatype
+    groups: dict[tuple[int, int], list] = {}
+    for p in polygons:
+        groups.setdefault((p.layer, p.datatype), []).append(p)
+    # shuffle the layer list
+    layers = sorted(groups)
+    random.Random(seed).shuffle(layers)
+    # return polygons according to the shuffled layer order
+    return [p for layer in layers for p in groups[layer]]
+
+
+# SVG render of the GDS
+def render_svg(
+    gds,
+    svg="gds_render.svg",
+    pad="5%",
+    filter_text=False,
+    filter_layers=None,
+    scramble_cells=None,
+):
+    library = gdstk.read_gds(gds)
+    top_cells = library.top_level()
+    assert len(top_cells) == 1
+    top_cell = top_cells[0]
+    assert isinstance(top_cell, gdstk.Cell)
+    cells = [top_cell] + [
+        cell for cell in top_cell.dependencies(True) if isinstance(cell, gdstk.Cell)
+    ]
+    for cell in cells:
+        if filter_text:
+            cell.remove(*cell.labels)
+        if filter_layers:
+            cell.filter(filter_layers)
+        if scramble_cells is not None:
+            if re.match(scramble_cells, cell.name):
+                polygons = cell.polygons
+                paths = cell.paths
+                cell.remove(*polygons, *paths)
+                path_polygons = [pp for p in paths for pp in p.to_polygons()]
+                cell.add(*scramble_polygons(polygons, cell.name))
+                cell.add(*scramble_polygons(path_polygons, cell.name))
+    top_cell.write_svg(svg, pad=pad)
+
+
+# Convert SVG to PNG using rsvg-convert or cairosvg
+def convert_svg_to_png(svg, png, force_cairo=False):
+    if force_cairo:
+        logging.warning("Falling back to cairosvg. This might take a while...")
+        cairosvg.svg2png(url=svg, write_to=png)
+    else:
+        cmd = f"rsvg-convert --unlimited {svg} -o {png} --no-keep-image-data"
+        logging.debug(cmd)
+        p = subprocess.run(cmd, shell=True, capture_output=True)
+        if p.returncode == 127:
+            logging.warning(
+                'rsvg-convert not found; is package "librsvg2-bin" installed?'
+            )
+            # fall back to cairosvg
+            convert_svg_to_png(svg, png, force_cairo=True)
+        elif p.returncode != 0:
+            if b"cannot load more than" in p.stderr:
+                logging.warning(
+                    f'Too many SVG elements ("{p.stderr.decode().strip()}")'
+                )
+                raise SVGTooComplexError()
+            else:
+                logging.warning(
+                    f'rsvg-convert returned an error ("{p.stderr.decode().strip()}")'
+                )
+                # fall back to cairosvg
+                convert_svg_to_png(svg, png, force_cairo=True)
+
+
+# Try various QUICK methods to create a more-compressed PNG render of the GDS,
+# and fall back to cairosvg if it doesn't work. This is designed for speed,
+# and in particular for use by the GitHub Actions.
+# For more info, see:
+# https://github.com/TinyTapeout/tt-gds-action/issues/8
+def render_png(
+    gds,
+    svg="gds_render_preview.svg",
+    svg_alt="gds_render_preview_alt.svg",
+    png="gds_render_preview.png",
+    final_png="gds_render.png",
+    scramble_cells=None,
+    buried_layers=None,
+    quality="0-30",
+):
+    logging.info(f"Rendering SVG without text labels: {svg}")
+    render_svg(gds=gds, svg=svg, pad=0, filter_text=True, scramble_cells=scramble_cells)
+    try:
+        logging.info(f"Converting to PNG using rsvg-convert: {png}")
+        convert_svg_to_png(svg, png)
+    except SVGTooComplexError:
+        logging.info(f"Rendering SVG without text labels or buried layers: {svg_alt}")
+        render_svg(
+            gds=gds,
+            svg=svg_alt,
+            pad=0,
+            filter_text=True,
+            filter_layers=buried_layers,
+            scramble_cells=scramble_cells,
+        )
+        try:
+            logging.info(f"Converting to PNG using rsvg-convert: {png}")
+            convert_svg_to_png(svg_alt, png)
+        except SVGTooComplexError:
+            # Fall back to cairosvg, and since we're doing that, might as well use the original full-detail SVG anyway:
+            convert_svg_to_png(svg, png, force_cairo=True)
+
+    # By now we should have gds_render_preview.png
+
+    # Compress with pngquant:
+    logging.info(f"Compressing PNG further with pngquant to: {final_png}")
+
+    cmd = f"pngquant --quality {quality} --speed 1 --nofs --strip --force --output {final_png} {png}"
+    logging.debug(cmd)
+    p = subprocess.run(cmd, shell=True, capture_output=True)
+
+    if p.returncode == 127:
+        logging.warning(
+            'pngquant not found; is package "pngquant" installed? Using intermediate (uncompressed) PNG file'
+        )
+        os.rename(png, final_png)
+    elif p.returncode != 0:
+        logging.warning(
+            f'pngquant error {p.returncode} ("{p.stderr.decode().strip()}"). Using intermediate (uncompressed) PNG file'
+        )
+        os.rename(png, final_png)
+    logging.info(f"Final PNG is {final_png} ({os.path.getsize(final_png):,} bytes)")