diff --git a/lerobot/common/datasets/image_writer.py b/lerobot/common/datasets/image_writer.py
index 705fe73b..7b9ed0e4 100644
--- a/lerobot/common/datasets/image_writer.py
+++ b/lerobot/common/datasets/image_writer.py
@@ -19,8 +19,8 @@ import threading
 from pathlib import Path
 
 import numpy as np
+import PIL.Image
 import torch
-from PIL import Image
 
 DEFAULT_IMAGE_PATH = "{image_key}/episode_{episode_index:06d}/frame_{frame_index:06d}.png"
 
@@ -40,10 +40,27 @@ def safe_stop_image_writer(func):
     return wrapper
 
 
-def write_image(image_array: np.ndarray, fpath: Path):
+def image_array_to_image(image_array: np.ndarray) -> PIL.Image.Image:
+    # TODO(aliberts): handle 1 channel and 4 for depth images
+    if image_array.ndim == 3 and image_array.shape[0] in [1, 3]:
+        # Transpose from pytorch convention (C, H, W) to (H, W, C)
+        image_array = image_array.transpose(1, 2, 0)
+    if image_array.dtype != np.uint8:
+        # Assume the image is in [0, 1] range for floating-point data
+        image_array = np.clip(image_array, 0, 1)
+        image_array = (image_array * 255).astype(np.uint8)
+    return PIL.Image.fromarray(image_array)
+
+
+def write_image(image: np.ndarray | PIL.Image.Image, fpath: Path):
     try:
-        image = Image.fromarray(image_array)
-        image.save(fpath)
+        if isinstance(image, np.ndarray):
+            img = image_array_to_image(image)
+        elif isinstance(image, PIL.Image.Image):
+            img = image
+        else:
+            raise TypeError(f"Unsupported image type: {type(image)}")
+        img.save(fpath)
     except Exception as e:
         print(f"Error writing image {fpath}: {e}")
 
@@ -63,7 +80,6 @@ def worker_process(queue: queue.Queue, num_threads: int):
     threads = []
     for _ in range(num_threads):
         t = threading.Thread(target=worker_thread_process, args=(queue,))
-        t.daemon = True
         t.start()
         threads.append(t)
     for t in threads:
@@ -95,6 +111,10 @@ class ImageWriter:
         self.queue = None
         self.threads = []
         self.processes = []
+        self._stopped = False
+
+        if num_threads <= 0 and num_processes <= 0:
+            raise ValueError("Number of threads and processes must be greater than zero.")
 
         if self.num_processes == 0:
             # Use threading
@@ -109,7 +129,6 @@ class ImageWriter:
             self.queue = multiprocessing.JoinableQueue()
             for _ in range(self.num_processes):
                 p = multiprocessing.Process(target=worker_process, args=(self.queue, self.num_threads))
-                p.daemon = True
                 p.start()
                 self.processes.append(p)
 
@@ -124,27 +143,33 @@ class ImageWriter:
             episode_index=episode_index, image_key=image_key, frame_index=0
         ).parent
 
-    def save_image(self, image_array: torch.Tensor | np.ndarray, fpath: Path):
-        if isinstance(image_array, torch.Tensor):
-            image_array = image_array.numpy()
-        self.queue.put((image_array, fpath))
+    def save_image(self, image: torch.Tensor | np.ndarray | PIL.Image.Image, fpath: Path):
+        if isinstance(image, torch.Tensor):
+            # Convert tensor to numpy array to minimize main process time
+            image = image.cpu().numpy()
+        self.queue.put((image, fpath))
 
     def wait_until_done(self):
         self.queue.join()
 
     def stop(self):
+        if self._stopped:
+            return
+
         if self.num_processes == 0:
-            # For threading
             for _ in self.threads:
                 self.queue.put(None)
             for t in self.threads:
                 t.join()
         else:
-            # For multiprocessing
             num_nones = self.num_processes * self.num_threads
             for _ in range(num_nones):
                 self.queue.put(None)
-            self.queue.close()
-            self.queue.join_thread()
             for p in self.processes:
                 p.join()
+                if p.is_alive():
+                    p.terminate()
+            self.queue.close()
+            self.queue.join_thread()
+
+        self._stopped = True
diff --git a/lerobot/common/datasets/lerobot_dataset.py b/lerobot/common/datasets/lerobot_dataset.py
index a2b889c8..bbeb25d6 100644
--- a/lerobot/common/datasets/lerobot_dataset.py
+++ b/lerobot/common/datasets/lerobot_dataset.py
@@ -590,7 +590,7 @@ class LeRobotDataset(torch.utils.data.Dataset):
                 img_path.parent.mkdir(parents=True, exist_ok=True)
 
             self.image_writer.save_image(
-                image_array=frame[cam_key],
+                image=frame[cam_key],
                 fpath=img_path,
             )
 
diff --git a/tests/fixtures/dataset_factories.py b/tests/fixtures/dataset_factories.py
index 52e6411e..b1136ffc 100644
--- a/tests/fixtures/dataset_factories.py
+++ b/tests/fixtures/dataset_factories.py
@@ -59,7 +59,7 @@ def img_array_factory():
 def img_factory(img_array_factory):
     def _create_img(width=100, height=100) -> PIL.Image.Image:
         img_array = img_array_factory(width=width, height=height)
-        return PIL.Image.Image.fromarray(img_array)
+        return PIL.Image.fromarray(img_array)
 
     return _create_img
 
diff --git a/tests/test_image_writer.py b/tests/test_image_writer.py
new file mode 100644
index 00000000..3f3045d0
--- /dev/null
+++ b/tests/test_image_writer.py
@@ -0,0 +1,385 @@
+import queue
+import time
+from multiprocessing import queues
+from unittest.mock import MagicMock, patch
+
+import numpy as np
+import pytest
+from PIL import Image
+
+from lerobot.common.datasets.image_writer import (
+    ImageWriter,
+    image_array_to_image,
+    safe_stop_image_writer,
+    write_image,
+)
+
+DUMMY_IMAGE = "test_image.png"
+
+
+def test_init_threading(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=0, num_threads=2)
+    try:
+        assert writer.num_processes == 0
+        assert writer.num_threads == 2
+        assert isinstance(writer.queue, queue.Queue)
+        assert len(writer.threads) == 2
+        assert len(writer.processes) == 0
+        assert all(t.is_alive() for t in writer.threads)
+    finally:
+        writer.stop()
+
+
+def test_init_multiprocessing(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    try:
+        assert writer.num_processes == 2
+        assert writer.num_threads == 2
+        assert isinstance(writer.queue, queues.JoinableQueue)
+        assert len(writer.threads) == 0
+        assert len(writer.processes) == 2
+        assert all(p.is_alive() for p in writer.processes)
+    finally:
+        writer.stop()
+
+
+def test_write_dir_created(tmp_path):
+    write_dir = tmp_path / "non_existent_dir"
+    assert not write_dir.exists()
+    writer = ImageWriter(write_dir=write_dir)
+    try:
+        assert write_dir.exists()
+    finally:
+        writer.stop()
+
+
+def test_get_image_file_path_and_episode_dir(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        episode_index = 1
+        image_key = "test_key"
+        frame_index = 10
+        expected_episode_dir = tmp_path / f"{image_key}/episode_{episode_index:06d}"
+        expected_path = expected_episode_dir / f"frame_{frame_index:06d}.png"
+        image_file_path = writer.get_image_file_path(episode_index, image_key, frame_index)
+        assert image_file_path == expected_path
+        episode_dir = writer.get_episode_dir(episode_index, image_key)
+        assert episode_dir == expected_episode_dir
+    finally:
+        writer.stop()
+
+
+def test_zero_threads(tmp_path):
+    with pytest.raises(ValueError):
+        ImageWriter(write_dir=tmp_path, num_processes=0, num_threads=0)
+
+
+def test_image_array_to_image_rgb(img_array_factory):
+    img_array = img_array_factory(100, 100)
+    result_image = image_array_to_image(img_array)
+    assert isinstance(result_image, Image.Image)
+    assert result_image.size == (100, 100)
+    assert result_image.mode == "RGB"
+
+
+def test_image_array_to_image_pytorch_format(img_array_factory):
+    img_array = img_array_factory(100, 100).transpose(2, 0, 1)
+    result_image = image_array_to_image(img_array)
+    assert isinstance(result_image, Image.Image)
+    assert result_image.size == (100, 100)
+    assert result_image.mode == "RGB"
+
+
+@pytest.mark.skip("TODO: implement")
+def test_image_array_to_image_single_channel(img_array_factory):
+    img_array = img_array_factory(channels=1)
+    result_image = image_array_to_image(img_array)
+    assert isinstance(result_image, Image.Image)
+    assert result_image.size == (100, 100)
+    assert result_image.mode == "L"
+
+
+def test_image_array_to_image_float_array(img_array_factory):
+    img_array = img_array_factory(dtype=np.float32)
+    result_image = image_array_to_image(img_array)
+    assert isinstance(result_image, Image.Image)
+    assert result_image.size == (100, 100)
+    assert result_image.mode == "RGB"
+    assert np.array(result_image).dtype == np.uint8
+
+
+def test_image_array_to_image_out_of_bounds_float():
+    # Float array with values out of [0, 1]
+    img_array = np.random.uniform(-1, 2, size=(100, 100, 3)).astype(np.float32)
+    result_image = image_array_to_image(img_array)
+    assert isinstance(result_image, Image.Image)
+    assert result_image.size == (100, 100)
+    assert result_image.mode == "RGB"
+    assert np.array(result_image).dtype == np.uint8
+    assert np.array(result_image).min() >= 0 and np.array(result_image).max() <= 255
+
+
+def test_write_image_numpy(tmp_path, img_array_factory):
+    image_array = img_array_factory()
+    fpath = tmp_path / DUMMY_IMAGE
+    write_image(image_array, fpath)
+    assert fpath.exists()
+    saved_image = np.array(Image.open(fpath))
+    assert np.array_equal(image_array, saved_image)
+
+
+def test_write_image_image(tmp_path, img_factory):
+    image_pil = img_factory()
+    fpath = tmp_path / DUMMY_IMAGE
+    write_image(image_pil, fpath)
+    assert fpath.exists()
+    saved_image = Image.open(fpath)
+    assert list(saved_image.getdata()) == list(image_pil.getdata())
+    assert np.array_equal(image_pil, saved_image)
+
+
+def test_write_image_exception(tmp_path):
+    image_array = "invalid data"
+    fpath = tmp_path / DUMMY_IMAGE
+    with patch("builtins.print") as mock_print:
+        write_image(image_array, fpath)
+        mock_print.assert_called()
+        assert not fpath.exists()
+
+
+def test_save_image_numpy(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_array = img_array_factory()
+        fpath = tmp_path / DUMMY_IMAGE
+        fpath.parent.mkdir(parents=True, exist_ok=True)
+        writer.save_image(image_array, fpath)
+        writer.wait_until_done()
+        assert fpath.exists()
+        saved_image = np.array(Image.open(fpath))
+        assert np.array_equal(image_array, saved_image)
+    finally:
+        writer.stop()
+
+
+def test_save_image_numpy_multiprocessing(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    try:
+        image_array = img_array_factory()
+        fpath = tmp_path / DUMMY_IMAGE
+        writer.save_image(image_array, fpath)
+        writer.wait_until_done()
+        assert fpath.exists()
+        saved_image = np.array(Image.open(fpath))
+        assert np.array_equal(image_array, saved_image)
+    finally:
+        writer.stop()
+
+
+def test_save_image_torch(tmp_path, img_tensor_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_tensor = img_tensor_factory()
+        fpath = tmp_path / DUMMY_IMAGE
+        fpath.parent.mkdir(parents=True, exist_ok=True)
+        writer.save_image(image_tensor, fpath)
+        writer.wait_until_done()
+        assert fpath.exists()
+        saved_image = np.array(Image.open(fpath))
+        expected_image = (image_tensor.permute(1, 2, 0).cpu().numpy() * 255).astype(np.uint8)
+        assert np.array_equal(expected_image, saved_image)
+    finally:
+        writer.stop()
+
+
+def test_save_image_torch_multiprocessing(tmp_path, img_tensor_factory):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    try:
+        image_tensor = img_tensor_factory()
+        fpath = tmp_path / DUMMY_IMAGE
+        writer.save_image(image_tensor, fpath)
+        writer.wait_until_done()
+        assert fpath.exists()
+        saved_image = np.array(Image.open(fpath))
+        expected_image = (image_tensor.permute(1, 2, 0).cpu().numpy() * 255).astype(np.uint8)
+        assert np.array_equal(expected_image, saved_image)
+    finally:
+        writer.stop()
+
+
+def test_save_image_pil(tmp_path, img_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_pil = img_factory()
+        fpath = tmp_path / DUMMY_IMAGE
+        fpath.parent.mkdir(parents=True, exist_ok=True)
+        writer.save_image(image_pil, fpath)
+        writer.wait_until_done()
+        assert fpath.exists()
+        saved_image = Image.open(fpath)
+        assert list(saved_image.getdata()) == list(image_pil.getdata())
+    finally:
+        writer.stop()
+
+
+def test_save_image_pil_multiprocessing(tmp_path, img_factory):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    try:
+        image_pil = img_factory()
+        fpath = tmp_path / DUMMY_IMAGE
+        writer.save_image(image_pil, fpath)
+        writer.wait_until_done()
+        assert fpath.exists()
+        saved_image = Image.open(fpath)
+        assert list(saved_image.getdata()) == list(image_pil.getdata())
+    finally:
+        writer.stop()
+
+
+def test_save_image_invalid_data(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_array = "invalid data"
+        fpath = writer.get_image_file_path(0, "test_key", 0)
+        fpath.parent.mkdir(parents=True, exist_ok=True)
+        with patch("builtins.print") as mock_print:
+            writer.save_image(image_array, fpath)
+            writer.wait_until_done()
+            mock_print.assert_called()
+            assert not fpath.exists()
+    finally:
+        writer.stop()
+
+
+def test_save_image_after_stop(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    writer.stop()
+    image_array = img_array_factory()
+    fpath = writer.get_image_file_path(0, "test_key", 0)
+    writer.save_image(image_array, fpath)
+    time.sleep(1)
+    assert not fpath.exists()
+
+
+def test_stop(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=0, num_threads=2)
+    writer.stop()
+    assert not any(t.is_alive() for t in writer.threads)
+
+
+def test_stop_multiprocessing(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    writer.stop()
+    assert not any(p.is_alive() for p in writer.processes)
+
+
+def test_multiple_stops(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path)
+    writer.stop()
+    writer.stop()  # Should not raise an exception
+    assert not any(t.is_alive() for t in writer.threads)
+
+
+def test_multiple_stops_multiprocessing(tmp_path):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    writer.stop()
+    writer.stop()  # Should not raise an exception
+    assert not any(t.is_alive() for t in writer.threads)
+
+
+def test_wait_until_done(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=0, num_threads=4)
+    try:
+        num_images = 100
+        image_arrays = [img_array_factory(width=500, height=500) for _ in range(num_images)]
+        fpaths = [writer.get_image_file_path(0, "test_key", i) for i in range(num_images)]
+        for image_array, fpath in zip(image_arrays, fpaths, strict=True):
+            fpath.parent.mkdir(parents=True, exist_ok=True)
+            writer.save_image(image_array, fpath)
+        writer.wait_until_done()
+        for i, fpath in enumerate(fpaths):
+            assert fpath.exists()
+            saved_image = np.array(Image.open(fpath))
+            assert np.array_equal(saved_image, image_arrays[i])
+    finally:
+        writer.stop()
+
+
+def test_wait_until_done_multiprocessing(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path, num_processes=2, num_threads=2)
+    try:
+        num_images = 100
+        image_arrays = [img_array_factory() for _ in range(num_images)]
+        fpaths = [writer.get_image_file_path(0, "test_key", i) for i in range(num_images)]
+        for image_array, fpath in zip(image_arrays, fpaths, strict=True):
+            fpath.parent.mkdir(parents=True, exist_ok=True)
+            writer.save_image(image_array, fpath)
+        writer.wait_until_done()
+        for i, fpath in enumerate(fpaths):
+            assert fpath.exists()
+            saved_image = np.array(Image.open(fpath))
+            assert np.array_equal(saved_image, image_arrays[i])
+    finally:
+        writer.stop()
+
+
+def test_exception_handling(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_array = img_array_factory()
+        with (
+            patch.object(writer.queue, "put", side_effect=queue.Full("Queue is full")),
+            pytest.raises(queue.Full) as exc_info,
+        ):
+            writer.save_image(image_array, tmp_path / "test.png")
+        assert str(exc_info.value) == "Queue is full"
+    finally:
+        writer.stop()
+
+
+def test_with_different_image_formats(tmp_path, img_array_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_array = img_array_factory()
+        formats = ["png", "jpeg", "bmp"]
+        for fmt in formats:
+            fpath = tmp_path / f"test_image.{fmt}"
+            write_image(image_array, fpath)
+            assert fpath.exists()
+    finally:
+        writer.stop()
+
+
+def test_safe_stop_image_writer_decorator():
+    class MockDataset:
+        def __init__(self):
+            self.image_writer = MagicMock(spec=ImageWriter)
+
+    @safe_stop_image_writer
+    def function_that_raises_exception(dataset=None):
+        raise Exception("Test exception")
+
+    dataset = MockDataset()
+
+    with pytest.raises(Exception) as exc_info:
+        function_that_raises_exception(dataset=dataset)
+
+    assert str(exc_info.value) == "Test exception"
+    dataset.image_writer.stop.assert_called_once()
+
+
+def test_main_process_time(tmp_path, img_tensor_factory):
+    writer = ImageWriter(write_dir=tmp_path)
+    try:
+        image_tensor = img_tensor_factory()
+        fpath = tmp_path / "test_main_process_time.png"
+        start_time = time.perf_counter()
+        writer.save_image(image_tensor, fpath)
+        end_time = time.perf_counter()
+        time_spent = end_time - start_time
+        # Might need to adjust this threshold depending on hardware
+        assert time_spent < 0.01, f"Main process time exceeded threshold: {time_spent}s"
+        writer.wait_until_done()
+        assert fpath.exists()
+    finally:
+        writer.stop()