Use zlib-ng to do ZIP compression

README.md

@@ -26,6 +26,7 @@ It takes one or more A1-sliced `.3mf` files, repeats their plate G-code accordin
 - Optional remaining-time plate-number encoding through `M73 R...`.
 - Combined mode: all input rows become one packed 3MF.
 - Individual batch mode: every input row becomes its own packed 3MF.
+- zlib-ng Deflate ZIP compression level, defaulting to Level 7.
 - GUI settings are saved to the program folder as `settings.json`.
 
 ## Installation for source use
@@ -352,6 +353,7 @@ Saved options include:
 - Final swap switch.
 - G-code patch switch.
 - Metadata mode.
+- ZIP compression level.
 - Individual batch mode.
 - Input handling options.
 - Output directory.

a1_swap_mod_packer/builder.py

@@ -6,6 +6,7 @@ import re
 import shutil
 import tempfile
 import zipfile
+from contextlib import contextmanager
 from pathlib import Path
 
 from .archive import GCODE_MEMBER_RE, MD5_MEMBER_RE, list_gcode_members
@@ -25,7 +26,7 @@ from .metadata import (
     safe_float,
     update_first_slice_info,
 )
-from .models import BuildOptions, BuildResult, GcodePatchConfig, PlateJob, PlateSource
+from .models import DEFAULT_ZIP_COMPRESS_LEVEL, BuildOptions, BuildResult, GcodePatchConfig, PlateJob, PlateSource
 from .patches import apply_gcode_patches, parse_patch_config
 
 try:
@@ -37,6 +38,34 @@ except Exception:  # pragma: no cover
 
 PREVIEW_MEMBER_RE = re.compile(r"^Metadata/plate_(\d+)(?:_small)?\.png$", re.IGNORECASE)
 MAX_COMPOSITE_PREVIEW_INPUTS = 9
+MIN_ZIP_COMPRESS_LEVEL = 1
+MAX_ZIP_COMPRESS_LEVEL = 9
+
+
+def normalized_zip_compress_level(level: int | None) -> int:
+    try:
+        value = int(level if level is not None else DEFAULT_ZIP_COMPRESS_LEVEL)
+    except (TypeError, ValueError):
+        value = DEFAULT_ZIP_COMPRESS_LEVEL
+    return min(MAX_ZIP_COMPRESS_LEVEL, max(MIN_ZIP_COMPRESS_LEVEL, value))
+
+
+def load_zlib_ng_module() -> object:
+    try:
+        from zlib_ng import zlib_ng
+    except ImportError as exc:  # pragma: no cover - exercised when dependency is missing
+        raise RuntimeError("zlib-ng is required for 3MF ZIP compression. Install it with: pip install zlib-ng") from exc
+    return zlib_ng
+
+
+@contextmanager
+def use_zlib_ng_for_zipfile() -> object:
+    original_zlib = zipfile.zlib
+    zipfile.zlib = load_zlib_ng_module()
+    try:
+        yield
+    finally:
+        zipfile.zlib = original_zlib
 
 
 def load_plate_sources(job: PlateJob) -> list[PlateSource]:
@@ -293,21 +322,28 @@ def preview_members_for_gcode_member(gcode_member: str) -> set[str]:
 
 def write_output_3mf(base_3mf: Path, output_3mf: Path, gcode_bytes: bytes, sources: list[PlateSource], options: BuildOptions) -> str:
     md5 = hashlib.md5(gcode_bytes).hexdigest()
-    with zipfile.ZipFile(base_3mf, "r") as src, zipfile.ZipFile(output_3mf, "w", compression=zipfile.ZIP_DEFLATED, compresslevel=1) as dst:
+    compress_level = normalized_zip_compress_level(options.zip_compress_level)
-        gcode_member = resolve_output_gcode_member(src, sources[0].member_name)
+    with use_zlib_ng_for_zipfile():
-        preview_members = preview_members_for_gcode_member(gcode_member)
+        with zipfile.ZipFile(base_3mf, "r") as src, zipfile.ZipFile(
-        for item in src.infolist():
+            output_3mf,
-            name = item.filename
+            "w",
-            if GCODE_MEMBER_RE.match(name) or MD5_MEMBER_RE.match(name):
+            compression=zipfile.ZIP_DEFLATED,
-                continue
+            compresslevel=compress_level,
-            data = src.read(name)
+        ) as dst:
-            if name == "Metadata/slice_info.config":
+            gcode_member = resolve_output_gcode_member(src, sources[0].member_name)
-                data = update_first_slice_info(data, sources, options)
+            preview_members = preview_members_for_gcode_member(gcode_member)
-            elif options.add_preview_label and name in preview_members:
+            for item in src.infolist():
-                data = compose_preview_image(data, sources, f"{len(sources)} P", small=name.endswith("_small.png"))
+                name = item.filename
-            dst.writestr(item, data)
+                if GCODE_MEMBER_RE.match(name) or MD5_MEMBER_RE.match(name):
-        dst.writestr(gcode_member, gcode_bytes)
+                    continue
-        dst.writestr(f"{gcode_member}.md5", md5)
+                data = src.read(name)
+                if name == "Metadata/slice_info.config":
+                    data = update_first_slice_info(data, sources, options)
+                elif options.add_preview_label and name in preview_members:
+                    data = compose_preview_image(data, sources, f"{len(sources)} P", small=name.endswith("_small.png"))
+                dst.writestr(item, data)
+            dst.writestr(gcode_member, gcode_bytes)
+            dst.writestr(f"{gcode_member}.md5", md5)
     return md5
 
 

a1_swap_mod_packer/cli.py

@@ -7,6 +7,7 @@ from pathlib import Path
 from . import APP_NAME, APP_TITLE, __version__
 from .core import (
     BuildOptions,
+    DEFAULT_ZIP_COMPRESS_LEVEL,
     PlateJob,
     build_packed_3mf,
     list_swap_gcode_files,
@@ -46,6 +47,7 @@ def build_command(args: argparse.Namespace) -> int:
         add_preview_label=not args.no_preview_label,
         apply_gcode_patches=not args.no_gcode_patches,
         swap_gcode_dir=Path(args.swap_gcode_dir) if args.swap_gcode_dir else None,
+        zip_compress_level=args.zip_level,
     )
     result = build_packed_3mf(jobs, options)
     print(f"Output: {result.output_3mf}")
@@ -91,6 +93,7 @@ def create_parser() -> argparse.ArgumentParser:
     build.add_argument("--no-swap-after-final", action="store_true", help="Do not run the swap G-code after the last plate.")
     build.add_argument("--metadata-mode", choices=("source", "sum"), default="source", help="How to write slice_info prediction and weight.")
     build.add_argument("--line-ending", choices=("lf", "crlf"), default="crlf", help="Line ending for the generated G-code.")
+    build.add_argument("--zip-level", type=int, choices=range(1, 10), default=DEFAULT_ZIP_COMPRESS_LEVEL, metavar="1-9", help="zlib-ng Deflate compression level for the output 3MF. Default: 7.")
     build.add_argument("--no-preview-label", action="store_true", help="Do not add a plate-count label to the first preview image.")
     build.add_argument("--no-gcode-patches", action="store_true", help=f"Do not apply editable patches from {default_patch_config_path()}.")
     build.set_defaults(func=build_command)

a1_swap_mod_packer/core.py

@@ -33,6 +33,7 @@ from .metadata import (
 )
 from .models import (
     DEFAULT_INSERT_BEFORE_MARKER,
+    DEFAULT_ZIP_COMPRESS_LEVEL,
     BuildOptions,
     BuildResult,
     BuildSummary,
@@ -59,6 +60,7 @@ from .planning import (
 __all__ = [
     "DEFAULT_INSERT_BEFORE_MARKER",
     "DEFAULT_OUTPUT_PATTERN",
+    "DEFAULT_ZIP_COMPRESS_LEVEL",
     "GCODE_MEMBER_RE",
     "M73_RE",
     "MD5_MEMBER_RE",

a1_swap_mod_packer/gui.py

@@ -46,6 +46,7 @@ except ImportError as exc:  # pragma: no cover
 from . import APP_NAME, APP_TITLE
 from .core import (
     BuildOptions,
+    DEFAULT_ZIP_COMPRESS_LEVEL,
     PlateJob,
     ThreeMfSummary,
     build_packed_3mf,
@@ -446,6 +447,14 @@ class MainWindow(QMainWindow):
         self.metadata_combo.setFixedWidth(260)
         options_layout.addRow("3MF metadata", self.metadata_combo)
 
+        self.zip_level_combo = QComboBox()
+        for level in range(1, 10):
+            self.zip_level_combo.addItem(f"Level {level}", level)
+        self.zip_level_combo.setCurrentIndex(DEFAULT_ZIP_COMPRESS_LEVEL - 1)
+        self.zip_level_combo.setFixedWidth(120)
+        self.zip_level_combo.setToolTip("zlib-ng Deflate compression level for the output 3MF.")
+        options_layout.addRow("ZIP compression", self.zip_level_combo)
+
         self.individual_batch_check = QCheckBox("Individual batch mode")
         self.individual_batch_check.setToolTip(
             "Build each input row as a separate output file, using that row's copy count."
@@ -528,6 +537,7 @@ class MainWindow(QMainWindow):
         self.swap_final_check.stateChanged.connect(self.save_current_settings)
         self.patch_check.stateChanged.connect(self.save_current_settings)
         self.metadata_combo.currentIndexChanged.connect(self.save_current_settings)
+        self.zip_level_combo.currentIndexChanged.connect(self.save_current_settings)
         self.individual_batch_check.stateChanged.connect(self.on_individual_batch_toggled)
         self.clear_after_build_check.stateChanged.connect(self.save_current_settings)
         self.skip_duplicates_check.stateChanged.connect(self.save_current_settings)
@@ -554,6 +564,13 @@ class MainWindow(QMainWindow):
         metadata_index = self.metadata_combo.findData(metadata_mode)
         if metadata_index >= 0:
             self.metadata_combo.setCurrentIndex(metadata_index)
+        try:
+            zip_level = int(options.get("zip_compress_level", DEFAULT_ZIP_COMPRESS_LEVEL))
+        except (TypeError, ValueError):
+            zip_level = DEFAULT_ZIP_COMPRESS_LEVEL
+        zip_level_index = self.zip_level_combo.findData(min(9, max(1, zip_level)))
+        if zip_level_index >= 0:
+            self.zip_level_combo.setCurrentIndex(zip_level_index)
         swap_gcode = options.get("swap_gcode") or self._settings.get("last_swap_gcode")
         if swap_gcode:
             index = self.swap_gcode_combo.findData(str(swap_gcode))
@@ -573,6 +590,7 @@ class MainWindow(QMainWindow):
             "swap_after_final": self.swap_final_check.isChecked(),
             "apply_gcode_patches": self.patch_check.isChecked(),
             "metadata_mode": self.metadata_combo.currentData(),
+            "zip_compress_level": int(self.zip_level_combo.currentData() or DEFAULT_ZIP_COMPRESS_LEVEL),
             "individual_batch_mode": self.individual_batch_check.isChecked(),
             "clear_after_build": self.clear_after_build_check.isChecked(),
             "skip_duplicates": self.skip_duplicates_check.isChecked(),
@@ -1062,6 +1080,7 @@ class MainWindow(QMainWindow):
             swap_after_final=self.swap_final_check.isChecked(),
             metadata_mode=self.metadata_combo.currentData(),
             apply_gcode_patches=self.patch_check.isChecked(),
+            zip_compress_level=int(self.zip_level_combo.currentData() or DEFAULT_ZIP_COMPRESS_LEVEL),
         )
 
     def log_build_result(self, result: Any) -> None:

a1_swap_mod_packer/models.py

@@ -5,6 +5,7 @@ from pathlib import Path
 from typing import Literal
 
 DEFAULT_INSERT_BEFORE_MARKER = ";=====printer finish  sound========="
+DEFAULT_ZIP_COMPRESS_LEVEL = 7
 
 MetadataMode = Literal["source", "sum"]
 LineEnding = Literal["lf", "crlf"]
@@ -45,6 +46,7 @@ class BuildOptions:
     add_preview_label: bool = True
     apply_gcode_patches: bool = True
     swap_gcode_dir: Path | None = None
+    zip_compress_level: int = DEFAULT_ZIP_COMPRESS_LEVEL
 
 
 @dataclass

requirements.txt

@@ -1,2 +1,3 @@
 PySide6>=6.6
 Pillow>=10.0
+zlib-ng>=0.5

tests/test_active_plate_member.py

@@ -7,6 +7,7 @@ import zipfile
 from pathlib import Path
 
 from a1_swap_mod_packer.builder import (
+    normalized_zip_compress_level,
     preview_members_for_gcode_member,
     resolve_output_gcode_member,
     select_preview_sources,
@@ -62,6 +63,44 @@ class ActivePlateMemberTest(unittest.TestCase):
                 self.assertEqual(archive.read("Metadata/plate_2.gcode.md5").decode(), md5)
                 self.assertEqual(md5, hashlib.md5(gcode_bytes).hexdigest())
 
+    def test_write_output_honors_zip_compression_level(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            source_3mf = root / "plate2.3mf"
+            level_1_output = root / "level1.3mf"
+            level_7_output = root / "level7.3mf"
+            self.write_plate2_archive(source_3mf)
+            sources = [
+                PlateSource(
+                    source_3mf=source_3mf,
+                    member_name="Metadata/plate_2.gcode",
+                    gcode_text="G1 X0\n",
+                )
+            ]
+            gcode_bytes = (b"G1 X123.456 Y789.012 E0.03456 ; repeated movement\n" * 20000)
+
+            for output_3mf, zip_level in ((level_1_output, 1), (level_7_output, 7)):
+                options = BuildOptions(
+                    swap_gcode="",
+                    output_3mf=output_3mf,
+                    add_preview_label=False,
+                    apply_gcode_patches=False,
+                    zip_compress_level=zip_level,
+                )
+                write_output_3mf(source_3mf, output_3mf, gcode_bytes, sources, options)
+
+            with zipfile.ZipFile(level_1_output, "r") as level_1_archive, zipfile.ZipFile(level_7_output, "r") as level_7_archive:
+                level_1_info = level_1_archive.getinfo("Metadata/plate_2.gcode")
+                level_7_info = level_7_archive.getinfo("Metadata/plate_2.gcode")
+                self.assertEqual(level_1_info.compress_type, zipfile.ZIP_DEFLATED)
+                self.assertEqual(level_7_info.compress_type, zipfile.ZIP_DEFLATED)
+                self.assertLess(level_7_info.compress_size, level_1_info.compress_size)
+
+    def test_zip_compression_level_is_clamped(self) -> None:
+        self.assertEqual(normalized_zip_compress_level(None), 7)
+        self.assertEqual(normalized_zip_compress_level(0), 1)
+        self.assertEqual(normalized_zip_compress_level(10), 9)
+
     def test_preview_composite_uses_first_nine_unique_input_files(self) -> None:
         if Image is None:
             self.skipTest("Pillow is not installed")