Return images same mode (initial commit) (#132)

Summary:
## Related Issue
Fixes #{128}

- [x] I have read CONTRIBUTING.md to understand how to contribute to this repository :)
- [x] Add src_mode arg to ret_and_save_image() in image/utils/utils.py
- [x] Pass src_mode arg into ret_and_save_image() from every augmentation except convert_color in image/functional.py (e.g. here for apply_lambda)
- [x] In image test evaluate_class(), assert that the mode of self.img & dst are equal.
- [x] Run image tests, make sure they all pass: python -m unittest discover -s augly/tests/image_tests/ -p "*"

## Unit Tests
If your changes touch the `audio` module, please run all of the `audio` tests and paste the output here. Likewise for `image`, `text`, & `video`. If your changes could affect behavior in multiple modules, please run the tests for all potentially affected modules. If you are unsure of which modules might be affected by your changes, please just run all the unit tests.

### [Image](url)

```bash
python -m unittest discover -s augly/tests/image_tests/ -p "*_test.py"
# Or `python -m unittest discover -s augly/tests/image_tests/ -p "*.py"` to run pytorch test too (must install `torchvision` to run)
```

Test Output:
n/a

## Other testing

N/A

Pull Request resolved: #132

Test Plan:
- Added line to transforms unit test saving dst image in `/tmp/`
- Ran transforms unit test

```
$ manifold rm ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_compose.png && manifold put /tmp/test_compose.png ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_compose.png
$ manifold rm ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_opacity.png && manifold put /tmp/test_opacity.png ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_opacity.png
$ manifold rm ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_emoji.png && manifold put /tmp/test_overlay_emoji.png ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_emoji.png
$ manifold rm ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_image.png && manifold put /tmp/test_overlay_image.png ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_image.png
$ manifold rm ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_onto_background_image.png && manifold put /tmp/test_overlay_onto_background_image.png ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_onto_background_image.png
$ manifold rm ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_onto_screenshot.png && manifold put /tmp/test_overlay_onto_screenshot.png ai_red_team/tree/augmentations/tests/image/dfdc_expected_output/test_overlay_onto_screenshot.png
```

```
$ rm -rf /home/zoep/.torch/iopath_cache/manifold_cache
$ buck test //aml/augly/tests/image_tests:transforms_unit_test
Summary
  Pass: 40
  Skip: 2
    ↻ aml/augly/tests/image_tests:transforms_unit_test - test_RandomEmojiOverlay (augly.tests.image_tests.transforms_unit_test.TransformsImageUnitTest)
    ↻ aml/augly/tests/image_tests:transforms_unit_test - test_MemeFormat (augly.tests.image_tests.transforms_unit_test.TransformsImageUnitTest)
  Omit: 1
    {emoji:2702} aml/augly/tests/image_tests:transforms_unit_test - test_OverlayText (augly.tests.image_tests.transforms_unit_test.TransformsImageUnitTest)
  ListingSuccess: 1
```

```
$ buck test //aml/augly/tests/image_tests:functional_unit_test
Summary
  Pass: 34
  Skip: 2
    ↻ aml/augly/tests/image_tests:functional_unit_test - test_overlay_text (augly.tests.image_tests.functional_unit_test.FunctionalImageUnitTest)
    ↻ aml/augly/tests/image_tests:functional_unit_test - test_meme_format (augly.tests.image_tests.functional_unit_test.FunctionalImageUnitTest)
  ListingSuccess: 1
```

Reviewed By: jbitton

Differential Revision: D31503672

Pulled By: zpapakipos

fbshipit-source-id: afcff9edaf791e2fe9ba3c45dbe9f7228b5f4d7b

Author: membriux

augly/assets/tests/image/dfdc_expected_output/test_compose.png

@@ -30,7 +30,12 @@ def validate_and_load_image(image: Union[str, Image.Image]) -> Image.Image:
     return image
 
 
-def ret_and_save_image(image: Image.Image, output_path: Optional[str]) -> Image.Image:
+def ret_and_save_image(
+    image: Image.Image, output_path: Optional[str], src_mode: Optional[str] = None
+) -> Image.Image:
+    if src_mode is not None:
+        image = image.convert(src_mode)
+
     if output_path is not None:
         if any(output_path.endswith(extension) for extension in JPEG_EXTENSIONS):
             image = image.convert("RGB")

augly/assets/tests/image/dfdc_expected_output/test_opacity.png

@@ -96,6 +96,7 @@ def evaluate_class(
         transform_class: Callable[..., Image.Image],
         fname: str,
         metadata_exclude_keys: Optional[List[str]] = None,
+        check_mode: bool = True,
     ):
         metadata = []
         bboxes, bbox_format = [(0.5, 0.5, 0.25, 0.75)], "yolo"
@@ -104,6 +105,9 @@ def evaluate_class(
             self.img, metadata=metadata, bboxes=bboxes, bbox_format=bbox_format
         )
 
+        if check_mode:
+            self.assertTrue(self.img.mode == dst.mode)
+
         self.assertTrue(
             are_equal_metadata(metadata, self.metadata[fname], metadata_exclude_keys)
         )

augly/assets/tests/image/dfdc_expected_output/test_overlay_emoji.png

@@ -67,7 +67,11 @@ def test_Contrast(self):
         self.evaluate_class(imaugs.Contrast(), fname="contrast")
 
     def test_ConvertColor(self):
-        self.evaluate_class(imaugs.ConvertColor(mode="L"), fname="convert_color")
+        self.evaluate_class(
+            imaugs.ConvertColor(mode="L"),
+            fname="convert_color",
+            check_mode=False,
+        )
 
     def test_Crop(self):
         self.evaluate_class(imaugs.Crop(), fname="crop")