feat(python): add cast_image function to itkwasm package

packages/core/python/itkwasm/itkwasm/__init__.py

@@ -1,6 +1,6 @@
 """itkwasm: Python interface to itk-wasm WebAssembly modules."""
 
-__version__ = "1.0b105"
+__version__ = "1.0b128"
 
 from .interface_types import InterfaceTypes
 from .image import Image, ImageType
@@ -19,6 +19,7 @@
 from .int_types import IntTypes
 from .pixel_types import PixelTypes
 from .environment_dispatch import environment_dispatch, function_factory
+from .cast_image import cast_image
 
 __all__ = [
   "InterfaceTypes",
@@ -43,4 +44,5 @@
   "PixelTypes",
   "environment_dispatch",
   "function_factory",
+  "cast_image",
   ]

packages/core/python/itkwasm/itkwasm/cast_image.py

@@ -0,0 +1,63 @@
+from typing import Optional
+from dataclasses import asdict
+import copy
+
+import numpy as np
+
+from .image import Image, ImageType
+from .pixel_types import PixelTypes
+from .int_types import IntTypes
+from .float_types import FloatTypes
+
+def cast_image(input_image: Image,
+               pixel_type: Optional[PixelTypes]=None,
+               component_type: Optional[IntTypes | FloatTypes]=None) -> Image:
+    """Cast an image to another pixel type and / or component type."""
+    output_image_type = ImageType(**asdict(input_image.imageType))
+
+    if pixel_type is not None:
+        output_image_type.pixelType = pixel_type
+        if pixel_type == PixelTypes.Scalar and output_image_type.components != 1:
+            raise ValueError("PixelType Scalar requires components == 1")
+
+    if component_type is not None and component_type != input_image.imageType.componentType:
+        output_image_type.componentType = component_type
+
+    output_image = Image(output_image_type)
+
+    output_image.name = input_image.name
+    output_image.origin = list(input_image.origin)
+    output_image.spacing = list(input_image.spacing)
+    output_image.direction = input_image.direction.copy()
+    output_image.size = list(input_image.size)
+    output_image.metadata = copy.deepcopy(input_image.metadata)
+
+    if input_image.data is not None:
+        if output_image_type.componentType == input_image.imageType.componentType:
+            output_image.data = input_image.data.copy()
+        else:
+            component_type = output_image_type.componentType
+            if component_type == IntTypes.UInt8:
+                output_image.data = input_image.data.astype(np.uint8)
+            elif component_type == IntTypes.Int8:
+                output_image.data = input_image.data.astype(np.int8)
+            elif component_type == IntTypes.UInt16:
+                output_image.data = input_image.data.astype(np.uint16)
+            elif component_type == IntTypes.Int16:
+                output_image.data = input_image.data.astype(np.int16)
+            elif component_type == IntTypes.UInt32:
+                output_image.data = input_image.data.astype(np.uint32)
+            elif component_type == IntTypes.Int32:
+                output_image.data = input_image.data.astype(np.int32)
+            elif component_type == IntTypes.UInt64:
+                output_image.data = input_image.data.astype(np.uint64)
+            elif component_type == IntTypes.Int64:
+                output_image.data = input_image.data.astype(np.int64)
+            elif component_type == FloatTypes.Float32:
+                output_image.data = input_image.data.astype(np.float32)
+            elif component_type == FloatTypes.Float64:
+                output_image.data = input_image.data.astype(np.float64)
+            else:
+                raise ValueError('Unsupported component type')
+
+    return output_image

packages/core/python/itkwasm/test/test_cast_image.py

@@ -0,0 +1,29 @@
+from pathlib import Path
+
+import itk
+
+from itkwasm import Image
+from itkwasm import FloatTypes, PixelTypes
+import numpy as np
+
+from itkwasm import cast_image
+
+def test_cast_image_component():
+    data = Path(__file__).absolute().parent / "input" / "cthead1.png"
+    itk_image = itk.imread(data, itk.UC)
+    itk_image_dict = itk.dict_from_image(itk_image)
+    itkwasm_image = Image(**itk_image_dict)
+
+    itkwasm_image_double = cast_image(itkwasm_image, component_type=FloatTypes.Float64)
+    assert itkwasm_image_double.imageType.componentType == FloatTypes.Float64
+    assert np.array_equal(itkwasm_image.data, itkwasm_image_double.data)
+
+def test_cast_image_pixel_type():
+    data = Path(__file__).absolute().parent / "input" / "cthead1.png"
+    itk_image = itk.imread(data, itk.UC)
+    itk_image_dict = itk.dict_from_image(itk_image)
+    itkwasm_image = Image(**itk_image_dict)
+
+    itkwasm_image_vector = cast_image(itkwasm_image, pixel_type=PixelTypes.VariableLengthVector)
+    assert itkwasm_image_vector.imageType.pixelType == PixelTypes.VariableLengthVector
+    assert np.array_equal(itkwasm_image.data, itkwasm_image_vector.data)

src/core/castImage.ts

@@ -5,7 +5,7 @@ import IntTypes from './IntTypes.js'
 import FloatTypes from './FloatTypes.js'
 
 /**
- * Cast an image to another PixelType or ComponentType
+ * Cast an image to another PixelType and/or ComponentType
  *
  * @param {Image} image - The input image
  * @param {CastImageOptions} options - specify the componentType and/or pixelType of the output