histolab · alessiamarcolini · Jul 1, 2021 · Jun 24, 2021
diff --git a/src/histolab/filters/image_filters.py b/src/histolab/filters/image_filters.py
@@ -329,7 +329,6 @@ class EosinChannel(ImageFilter):
     Example:
         >>> from PIL import Image
         >>> from histolab.filters.image_filters import EosinChannel
-        >>> from histolab.filters import image_filters_functional as imf
         >>> image_rgb = Image.open("tests/fixtures/pil-images-rgb/tcga-lung-rgb.png")
         >>> eosin_channel = EosinChannel()
         >>> image_e = eosin_channel(image_rgb)
@@ -340,6 +339,36 @@ def __call__(self, img):
         return eosin
 
 
+class DABChannel(ImageFilter):
+    """Obtain DAB channel from RGB image.
+
+    Input image is first converted into HED space and the DAB channel is
+    rescaled for increased contrast.
+
+    Parameters
+    ----------
+    img : Image.Image
+        Input RGB image
+
+    Returns
+    -------
+    Image.Image
+        Grayscale image corresponding to input image with DAB channel enhanced.
+
+
+    Example:
+        >>> from PIL import Image
+        >>> from histolab.filters.image_filters import DABChannel
+        >>> image_rgb = Image.open("tests/fixtures/pil-images-rgb/tcga-lung-rgb.png")
+        >>> dab_channel = DABChannel()
+        >>> image_d = dab_channel(image_rgb)
+    """  # noqa
+
+    def __call__(self, img):
+        dab = F.dab_channel(img)
+        return dab
+
+
 class RgbToHsv(ImageFilter):
     """Convert RGB channels to HSV channels.
 

diff --git a/src/histolab/filters/image_filters_functional.py b/src/histolab/filters/image_filters_functional.py
@@ -103,6 +103,29 @@ def blue_pen_filter(img: PIL.Image.Image) -> PIL.Image.Image:
     return apply_mask_image(img, blue_pen_filter_img)
 
 
+def dab_channel(img: PIL.Image.Image) -> PIL.Image.Image:
+    """Obtain DAB channel from RGB image.
+
+    Input image is first converted into HED space and the DAB channel is
+    rescaled for increased contrast.
+
+    Parameters
+    ----------
+    img : Image.Image
+        Input RGB image
+
+    Returns
+    -------
+    Image.Image
+        Grayscale image corresponding to input image with DAB channel enhanced.
+    """
+    if img.mode not in ["RGB", "RGBA"]:
+        raise ValueError("Input image must be RGB/RGBA.")
+    dab = np.array(rgb_to_hed(img))[:, :, 2]
+    dab = sk_exposure.rescale_intensity(dab)
+    return np_to_pil(dab)
+
+
 def eosin_channel(img: PIL.Image.Image) -> PIL.Image.Image:
     """Obtain Eosin channel from RGB image.
 

diff --git a/tests/expectations/pil-images-rgb/tcga-lung-rgb-dab-channel.png b/tests/expectations/pil-images-rgb/tcga-lung-rgb-dab-channel.png
diff --git a/tests/expectations/pil-images-rgba/tcga-lung-dab-channel.png b/tests/expectations/pil-images-rgba/tcga-lung-dab-channel.png
diff --git a/tests/integration/test_image_filters.py b/tests/integration/test_image_filters.py
@@ -1679,3 +1679,42 @@ def test_rgb_to_lab_raises_exception_on_gs_and_rgba_image(pil_image):
 
     assert isinstance(err.value, Exception)
     assert str(err.value) == "Input image must be RGB"
+
+
+def test_dab_channel_filter_with_rgb_image():
+    img = RGB.TCGA_LUNG_RGB
+    expected_value = load_expectation(
+        "pil-images-rgb/tcga-lung-rgb-dab-channel", type_="png"
+    )
+
+    dab_img = imf.dab_channel(img)
+
+    np.testing.assert_array_almost_equal(np.array(dab_img), np.array(expected_value))
+    assert np.unique(np.array(ImageChops.difference(dab_img, expected_value)))[0] == 0
+
+
+def test_dab_channel_filter_with_rgba_image():
+    img = RGBA.TCGA_LUNG
+    expected_value = load_expectation(
+        "pil-images-rgba/tcga-lung-dab-channel", type_="png"
+    )
+    expected_warning_regex = (
+        r"Input image must be RGB. NOTE: the image will be converted to RGB before"
+        r" HED conversion."
+    )
+
+    with pytest.warns(UserWarning, match=expected_warning_regex):
+        dab_img = imf.dab_channel(img)
+
+    np.testing.assert_array_almost_equal(np.array(dab_img), np.array(expected_value))
+    assert np.unique(np.array(ImageChops.difference(dab_img, expected_value)))[0] == 0
+
+
+def test_dab_channel_raises_exception_on_gs_image():
+    gs_img = GS.DIAGNOSTIC_SLIDE_THUMB_GS
+
+    with pytest.raises(ValueError) as err:
+        imf.dab_channel(gs_img)
+
+    assert isinstance(err.value, Exception)
+    assert str(err.value) == "Input image must be RGB/RGBA."
diff --git a/tests/unit/filters/test_image_filters.py b/tests/unit/filters/test_image_filters.py
@@ -408,3 +408,16 @@ def it_calls_rgb_to_lab_functional(self, request):
 
         F_rgb_to_lab.assert_called_once_with(image)
         assert type(rgb_to_lab(image)) == PIL.Image.Image
+
+    def it_calls_dab_channel_functional(self, request):
+        image = PILIMG.RGBA_COLOR_500X500_155_249_240
+        F_dab_channel = function_mock(
+            request, "histolab.filters.image_filters_functional.dab_channel"
+        )
+        F_dab_channel.return_value = image
+        dab_channel = imf.DABChannel()
+
+        dab_channel(image)
+
+        F_dab_channel.assert_called_once_with(image)
+        assert type(dab_channel(image)) == PIL.Image.Image