Incorrect color conversion in VisualizationDemo

[weitanism]

The VisualizationDemo converts input image color from BGR to RGB before invoking DefaultPredictor.__call__:

OneFormer/demo/predictor.py

Lines 52 to 53 in 4962ef6

	# Convert image from OpenCV BGR format to Matplotlib RGB format.
	image = image[:, :, ::-1]

But the DefaultPredictor.__call__ converts the color format again:

OneFormer/demo/defaults.py

Lines 71 to 73 in 4962ef6

	if self.input_format == "RGB":
	# whether the model expects BGR inputs or RGB
	original_image = original_image[:, :, ::-1]

It may cause worse performance compared to the huggingface demo.

Possible related issues: #115