feat: container for images (#159)

Closes #158.

### Summary of Changes

* New class `safeds.data.image.containers.Image` to store images
* An `Image` can be created from and saved to JPEG and PNG files
* Methods that create a plot for `Table` and `Column` now return an
`Image` instead of plotting them directly in an interactive environment
* An `Image` can be displayed in an interactive environment

---------

Co-authored-by: megalinter-bot <129584137+megalinter-bot@users.noreply.github.com>

pyproject.toml

@@ -14,11 +14,12 @@ packages = [
 
 [tool.poetry.dependencies]
 python = "^3.10"
+ipython = "^8.8.0"
+matplotlib = "^3.6.3"
 pandas = "^1.5.3"
+pillow = "^9.5.0"
 scikit-learn = "^1.2.0"
 seaborn = "^0.12.2"
-ipython = "^8.8.0"
-matplotlib = "^3.6.3"
 
 [tool.poetry.group.dev.dependencies]
 pytest = "^7.2.1"

src/safeds/data/image/__init__.py

@@ -0,0 +1 @@
+"""Work with image data."""

src/safeds/data/image/containers/__init__.py

@@ -0,0 +1,7 @@
+"""Classes that can store image data."""
+
+from ._image import Image
+
+__all__ = [
+    "Image",
+]

src/safeds/data/image/containers/_image.py

@@ -0,0 +1,153 @@
+from __future__ import annotations
+
+import io
+from pathlib import Path
+from typing import BinaryIO
+
+from PIL.Image import Image as PillowImage
+from PIL.Image import open as open_image
+
+from safeds.data.image.typing import ImageFormat
+
+
+class Image:
+    """
+    A container for image data.
+
+    Parameters
+    ----------
+    data : BinaryIO
+        The image data as bytes.
+    """
+
+    @staticmethod
+    def from_jpeg_file(path: str) -> Image:
+        """
+        Create an image from a JPEG file.
+
+        Parameters
+        ----------
+        path : str
+            The path to the JPEG file.
+
+        Returns
+        -------
+        image : Image
+            The image.
+        """
+        return Image(
+            data=Path(path).open("rb"),
+            format_=ImageFormat.JPEG,
+        )
+
+    @staticmethod
+    def from_png_file(path: str) -> Image:
+        """
+        Create an image from a PNG file.
+
+        Parameters
+        ----------
+        path : str
+            The path to the PNG file.
+
+        Returns
+        -------
+        image : Image
+            The image.
+        """
+        return Image(
+            data=Path(path).open("rb"),
+            format_=ImageFormat.PNG,
+        )
+
+    def __init__(self, data: BinaryIO, format_: ImageFormat):
+        data.seek(0)
+
+        self._image: PillowImage = open_image(data, formats=[format_.value])
+        self._format: ImageFormat = format_
+
+    # ------------------------------------------------------------------------------------------------------------------
+    # Properties
+    # ------------------------------------------------------------------------------------------------------------------
+
+    @property
+    def format(self) -> ImageFormat:
+        """
+        Get the image format.
+
+        Returns
+        -------
+        format : ImageFormat
+            The image format.
+        """
+        return self._format
+
+    # ------------------------------------------------------------------------------------------------------------------
+    # Conversion
+    # ------------------------------------------------------------------------------------------------------------------
+
+    def to_jpeg_file(self, path: str) -> None:
+        """
+        Save the image as a JPEG file.
+
+        Parameters
+        ----------
+        path : str
+            The path to the JPEG file.
+        """
+        Path(path).parent.mkdir(parents=True, exist_ok=True)
+        self._image.save(path, format="jpeg")
+
+    def to_png_file(self, path: str) -> None:
+        """
+        Save the image as a PNG file.
+
+        Parameters
+        ----------
+        path : str
+            The path to the PNG file.
+        """
+        Path(path).parent.mkdir(parents=True, exist_ok=True)
+        self._image.save(path, format="png")
+
+    # ------------------------------------------------------------------------------------------------------------------
+    # IPython integration
+    # ------------------------------------------------------------------------------------------------------------------
+
+    def _repr_jpeg_(self) -> bytes | None:
+        """
+        Return a JPEG image as bytes.
+
+        If the image is not a JPEG, return None.
+
+        Returns
+        -------
+        jpeg : bytes
+            The image as JPEG.
+        """
+        if self._format != ImageFormat.JPEG:
+            return None
+
+        buffer = io.BytesIO()
+        self._image.save(buffer, format="jpeg")
+        buffer.seek(0)
+        return buffer.read()
+
+    def _repr_png_(self) -> bytes | None:
+        """
+        Return a PNG image as bytes.
+
+        If the image is not a PNG, return None.
+
+        Returns
+        -------
+        png : bytes
+            The image as PNG.
+        """
+        if self._format != ImageFormat.PNG:
+            return None
+
+        buffer = io.BytesIO()
+        self._image.save(buffer, format="png")
+        buffer.seek(0)
+        return buffer.read()

src/safeds/data/image/typing/__init__.py

@@ -0,0 +1,7 @@
+"""Types used to distinguish different image formats."""
+
+from ._image_format import ImageFormat
+
+__all__ = [
+    "ImageFormat",
+]

src/safeds/data/image/typing/_image_format.py

@@ -0,0 +1,8 @@
+from enum import Enum
+
+
+class ImageFormat(Enum):
+    """Images formats supported by us."""
+
+    JPEG = "jpeg"
+    PNG = "png"

src/safeds/data/tabular/containers/_column.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import io
 from numbers import Number
 from typing import TYPE_CHECKING, Any
 
@@ -9,6 +10,8 @@
 import seaborn as sns
 from IPython.core.display_functions import DisplayHandle, display
 
+from safeds.data.image.containers import Image
+from safeds.data.image.typing import ImageFormat
 from safeds.data.tabular.typing import ColumnType
 from safeds.exceptions import (
     ColumnLengthMismatchError,
@@ -470,10 +473,15 @@ def variance(self) -> float:
     # Plotting
     # ------------------------------------------------------------------------------------------------------------------
 
-    def boxplot(self) -> None:
+    def boxplot(self) -> Image:
         """
         Plot this column in a boxplot. This function can only plot real numerical data.
 
+        Returns
+        -------
+        plot: Image
+            The plot as an image.
+
         Raises
         ------
         TypeError
@@ -487,13 +495,28 @@ def boxplot(self) -> None:
                     "The column contains complex data. Boxplots cannot plot the imaginary part of complex "
                     "data. Please provide a Column with only real numbers",
                 )
+
+        fig = plt.figure()
         ax = sns.boxplot(data=self._data)
         ax.set(xlabel=self.name)
         plt.tight_layout()
-        plt.show()
 
-    def histogram(self) -> None:
-        """Plot a column in a histogram."""
+        buffer = io.BytesIO()
+        fig.savefig(buffer, format="png")
+        plt.close()  # Prevents the figure from being displayed directly
+        buffer.seek(0)
+        return Image(buffer, ImageFormat.PNG)
+
+    def histogram(self) -> Image:
+        """
+        Plot a column in a histogram.
+
+        Returns
+        -------
+        plot: Image
+            The plot as an image.
+        """
+        fig = plt.figure()
         ax = sns.histplot(data=self._data)
         ax.set_xticks(ax.get_xticks())
         ax.set(xlabel=self.name)
@@ -503,23 +526,17 @@ def histogram(self) -> None:
             horizontalalignment="right",
         )  # rotate the labels of the x Axis to prevent the chance of overlapping of the labels
         plt.tight_layout()
-        plt.show()
+
+        buffer = io.BytesIO()
+        fig.savefig(buffer, format="png")
+        plt.close()  # Prevents the figure from being displayed directly
+        buffer.seek(0)
+        return Image(buffer, ImageFormat.PNG)
 
     # ------------------------------------------------------------------------------------------------------------------
-    # Other
+    # IPython integration
     # ------------------------------------------------------------------------------------------------------------------
 
-    def _count_missing_values(self) -> int:
-        """
-        Return the number of null values in the column.
-
-        Returns
-        -------
-        count : int
-            The number of null values.
-        """
-        return self._data.isna().sum()
-
     def _ipython_display_(self) -> DisplayHandle:
         """
         Return a display object for the column to be used in Jupyter Notebooks.
@@ -534,3 +551,18 @@ def _ipython_display_(self) -> DisplayHandle:
 
         with pd.option_context("display.max_rows", tmp.shape[0], "display.max_columns", tmp.shape[1]):
             return display(tmp)
+
+    # ------------------------------------------------------------------------------------------------------------------
+    # Other
+    # ------------------------------------------------------------------------------------------------------------------
+
+    def _count_missing_values(self) -> int:
+        """
+        Return the number of null values in the column.
+
+        Returns
+        -------
+        count : int
+            The number of null values.
+        """
+        return self._data.isna().sum()

src/safeds/data/tabular/containers/_row.py

@@ -165,7 +165,7 @@ def count(self) -> int:
         return len(self._data)
 
     # ------------------------------------------------------------------------------------------------------------------
-    # Other
+    # IPython integration
     # ------------------------------------------------------------------------------------------------------------------
 
     def _ipython_display_(self) -> DisplayHandle: