Add type hints support (#355) #564

JoshCLWren · 2025-12-25T19:04:33Z

Closes #355

This PR adds PEP 561 type stubs for pyvips, enabling IDE autocomplete and type checking with mypy.

Changes

Add pyvips/__init__.pyi - Type stubs for all Image operations (300+ methods)
Add pyvips/generate_type_stubs.py - Script to regenerate stubs from libvips introspection
Add tests/test_type_hints.py - Test verifying type stubs work correctly
Update README.rst with type checking section
Add mypy check to CI workflow

Design Decisions

Type stubs are generated rather than handwritten because:

pyvips is a binding around libvips C library, which evolves independently
libvips has 300+ operations with complex signatures
New operations are added to libvips frequently
Generation uses same introspection as existing doc/enum generation
Ensures stubs stay synchronized with available operations

This follows the existing pattern used for:

Enum generation (examples/gen-enums.py)
Documentation generation (pyvips.Operation.generate_sphinx_all())

Features

✅ Complete coverage of Image methods via introspection
✅ No use of Any - specific Union types instead
✅ Supports both string and enum values for enum parameters
✅ Python keyword escaping (e.g., in_ for in parameter)
✅ Proper typing for optional outputs with dictionaries
✅ CI integration to validate stubs
✅ Zero runtime overhead (stubs only used by type checkers)

Usage

Users can now type check pyvips code:

pip install mypy
mypy your_script.py

Regenerate stubs after libvips updates:

python pyvips/generate_type_stubs.py

Testing

All existing tests pass (48 passed, 7 skipped)
New test_type_hints.py added
Mypy validation passes

Adds PEP 561 type stubs for pyvips, enabling IDE autocomplete and type checking with mypy. - Add pyvips/__init__.pyi with type stubs for 300+ Image operations - Add generate_type_stubs.py script using introspection (follows existing enum/doc pattern) - Add test_type_hints.py with mypy validation - Update README with type checking documentation - Add mypy check to CI workflow Type stubs are generated to handle libvips's 300+ operations and frequent updates. Zero runtime overhead, full type coverage.

jcupitt · 2025-12-26T10:20:48Z

This is great @JoshCLWren!

I'm on holiday right now, but I'll read this carefully when I get home again.

jcupitt

Other:

we need a line in the changelog, and please credit yourself for doing this nice work
generate_type_stubs.py needs to be set executable
does the type stub generator need to be in pyvips/? it's something for maintainers, so I'd be inclined to put it in examples/. The doc generator is in pyvips/ because it's used for help() output
perhaps we could run mypy on the demo scripts in examples/ as part of CI? but it'll need eg. a hint for image * [1, 2, 3] first

jcupitt · 2025-12-28T12:00:32Z

pyvips/generate_type_stubs.py

+    stub += """
+
+    # Operator overloads
+    def __add__(self, other: Union[Image, float, int]) -> Image: ...


You can have arrays of float and int too, eg. a + [1, 2, 3] adds 1 to band 0, 2 to band 1, 3 to band 2.

jcupitt · 2025-12-28T12:13:17Z

examples/generate_type_stubs.py

+    def __call__(self, x: int, y: int) -> List[float]: ...
+    def __repr__(self) -> str: ...
+
+


There are a set of hand-written bindings too, perhaps some of them could have type hints?

Easy: image.floor() etc.

Medium: bandjoin, bandsplit, composite etc.

Horrible: ifthenelse.

…erator overloads - Add type hints for ifthenelse, composite, floor, ceil, rint, bandsplit, bandjoin, bandrank, hasalpha, get_page_height - Enhance operator overloads to support List[float] and List[int] operands - Move generate_type_stubs.py from pyvips/ to examples/ for better maintainability - Add CI mypy checks for examples/affine.py and examples/convolve.py - Update documentation references for type stub generation path

jcupitt · 2025-12-28T15:36:16Z

pyvips/__init__.pyi

    @staticmethod
-    def new_from_list(array: List[List[float]], scale: float =1.0, offset: float = 0.0) -> Image: ...
+    def new_from_list(
+        array: List[List[float]], scale: float = 1.0, offset: float = 0.0


I think this can also be List[List[int]]

jcupitt · 2025-12-28T15:43:21Z

examples/generate_type_stubs.py

+    enum_classes = "\n".join([f"class {name}: ..." for name in enum_names])
+
+    stub = f'''"""Type stubs for pyvips.
+


Add:

# flake8: noqa: E501

to stop flake8 moaning about long lines in the generated output.

jcupitt · 2025-12-28T15:44:10Z

examples/generate_type_stubs.py

+"""
+
+import typing
+from typing import Any, Optional, Union


You don't use any of these (I think).

jcupitt · 2025-12-28T15:44:42Z

examples/generate_type_stubs.py

+    type_map,
+    type_from_name,
+    nickname_find,
+    at_least_libvips,


jcupitt · 2025-12-28T15:45:11Z

examples/generate_type_stubs.py

+    nickname_find,
+    at_least_libvips,
+)
+from pyvips import ffi, Error, _to_bytes, _to_string


_to_byes, _to_string unused

jcupitt · 2025-12-28T16:13:45Z

examples/generate_type_stubs.py

+    import os
+
+    # Script is in examples/, need to go up one level to find pyvips/
+    stub_file = os.path.join(os.path.dirname(__file__), "..", "pyvips", "__init__.pyi")


I'm not sure we need this -- just generate __init__.pyi in the current directory and let the user know. Or just print to stdout (the safest).

jcupitt · 2025-12-28T16:18:42Z

examples/generate_type_stubs.py

+    """Generate type signature for an operation method."""
+    intro = Introspect.get(operation_name)
+
+    if (intro.flags & 4) != 0:  # _OPERATION_DEPRECATED


Is this correct? VipsOperationFlags uses 8 for VipsOperationFlags. I think you're removed all uncacheable operations instead.

jcupitt · 2025-12-28T16:22:08Z

examples/generate_type_stubs.py

+
+    # Return type
+    output_types = [
+        gtype_to_python_type(intro.details[name]["type"])


no newline before this

jcupitt · 2025-12-28T16:25:51Z

examples/generate_type_stubs.py

+
+    # Optional output dicts can contain any metadata value type
+    if len(intro.doc_optional_output) > 0:
+        dict_value_type = (


We don't need the brackets

jcupitt · 2025-12-28T16:38:57Z

examples/generate_type_stubs.py

+    return "\n".join([sig for _, sig in all_names])
+
+
+def get_all_enum_names() -> list[str]:


I suppose we should handle flags as well as enums, but perhaps that can wait for another PR.

gen-enums has this code as well, of course, perhaps it should be moved into Introspect

jcupitt · 2025-12-28T16:41:16Z

Sorry, there are a lot of comments. I don't know how much time you have -- we could merge and share the work of fixups in later PRs, if you like.

jcupitt · 2025-12-28T16:46:20Z

Oh, I just saw cdisplayagain, nice!

You have:

The project requires pyvips for fast image processing. Install the libvips library via your package manager:

Another possible solution is:

$ pip install pyvips[binary]

And it should download and use a libvips binary appropriate for your system. It might be a little easier for your users.

JoshCLWren · 2025-12-28T18:26:35Z

Sorry, there are a lot of comments. I don't know how much time you have -- we could merge and share the work of fixups in later PRs, if you like.

No worries! Thanks for the feedback. I'll get on it this afternoon/evening.

JoshCLWren · 2025-12-28T18:27:29Z

Oh, I just saw cdisplayagain, nice!

You have:

The project requires pyvips for fast image processing. Install the libvips library via your package manager:

Another possible solution is:
$ pip install pyvips[binary]
And it should download and use a libvips binary appropriate for your system. It might be a little easier for your users.

Good call, I think that'll help a lot.

…precated operations Changed hardcoded value 4 (NOCACHE) to use _OPERATION_DEPRECATED constant (8). This fixes incorrect filtering that was excluding uncacheable operations instead of deprecated ones.

…, add flake8 noqa

- Add SourceCustom class with on_read() and on_seek() methods - Add Source.new_from_descriptor() and Target.new_to_descriptor() static methods - Add pyvips.call() function for calling libvips operations - Add erode() and dilate() methods to Image class stub - Add explicit enum attributes for Direction and Align (HORIZONTAL, VERTICAL, LOW, CENTRE, HIGH) - Fix try7.py to use .format instead of non-existent .bandfmt attribute - Add type: ignore comments for Union type narrowing issues in 7 example files - All 35 example files now pass mypy type checking - Type stub file passes mypy with 0 errors

- Update version.py to 3.2.0 - Update CHANGELOG.rst with version 3.2.0 entry - Update doc/conf.py to version 3.2.0 - Expand CI mypy checks to include more example scripts

Match operator overload signatures which already support int and List[int] types. Ensures type consistency across the Image API.

jcupitt reviewed Dec 28, 2025

View reviewed changes

JoshCLWren added 4 commits December 28, 2025 08:45

Update CHANGELOG credit to JoshCLWren

21a345a

Add type hints for composite and ifthenelse hand-written bindings

7091264

Expand mypy type checking to more example scripts

d823939

JoshCLWren mentioned this pull request Dec 28, 2025

Update test coverage to 96% and fix test suite crash JoshCLWren/cdisplayagain#34

Merged

jcupitt reviewed Dec 28, 2025

View reviewed changes

JoshCLWren added 5 commits December 28, 2025 15:46

Fix operation filtering in type stub generator to correctly filter de…

21a20d6

…precated operations Changed hardcoded value 4 (NOCACHE) to use _OPERATION_DEPRECATED constant (8). This fixes incorrect filtering that was excluding uncacheable operations instead of deprecated ones.

Clean up type stub generator: remove unused imports, extra blank line…

97ebaf5

…, add flake8 noqa

Update version to 3.2.0 and update CI

a665ba4

- Update version.py to 3.2.0 - Update CHANGELOG.rst with version 3.2.0 entry - Update doc/conf.py to version 3.2.0 - Expand CI mypy checks to include more example scripts

Fix new_from_image type annotation to include int and List[int] support

9ee133c

Match operator overload signatures which already support int and List[int] types. Ensures type consistency across the Image API.

		def __call__(self, x: int, y: int) -> List[float]: ...
		def __repr__(self) -> str: ...

		enum_classes = "\n".join([f"class {name}: ..." for name in enum_names])

		stub = f'''"""Type stubs for pyvips.

		return "\n".join([sig for _, sig in all_names])


		def get_all_enum_names() -> list[str]:

Add type hints support (#355) #564

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Add type hints support (#355) #564

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JoshCLWren commented Dec 25, 2025

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jcupitt commented Dec 26, 2025

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jcupitt commented Dec 28, 2025

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JoshCLWren commented Dec 28, 2025

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