Add preprocessing common to OCR tasks

[UserUnknownFactor]

Common OCR tasks often include filling transparent areas with actual color, inverting image or its binarization. This commits adds those as optional parameters for ocr function.

[paddle-bot]

Thanks for your contribution!

[shiyutang]

The solution is solid but I feel it is a bit redundant to expose all the image processing params in PaddleOCR.ocr，do we have a better solution to

[UserUnknownFactor]

@shiyutang How about this?

[shiyutang]

I think your edit is great, but there is one thing I want to add;

Args is passed into PaddleOCR in L662, therefore the preprocess args is already in the engine and can be accessed through self.params.binarize. This can avoid directly passing it into the engine. ocr.

engine = PaddleOCR(**(args.__dict__))

[UserUnknownFactor]

Args is passed into PaddleOCR in L662, therefore the preprocess args is already in the engine and can be accessed

But what if we want to use those options through the API and not from the console application parameters? Won't this make things difficult because we'll need to reconfigure engine parameters then?

[shiyutang]

In the above way, if we need to use image preprocess options through API, we can directly pass the params into PaddleOCR.

PaddleOCR(bin=True,..)

[shiyutang]

On top of code change, we may also need to update the docs. https://github.com/PaddlePaddle/PaddleOCR/blob/release/2.6/doc/doc_ch/inference_args.md
https://github.com/PaddlePaddle/PaddleOCR/blob/release/2.6/doc/doc_en/inference_args.md

[UserUnknownFactor]

PaddleOCR(bin=True,..)

It will prevent us from changing the settings on per-file basis, and it is needed sometimes.
So I think the current implementation is the best compromise.

doc_en/inference_args.md

This doesn't exist. Do you want me to create it? I don't know Chinese, though...

[shiyutang]

OK~ you can add here:https://github.com/PaddlePaddle/PaddleOCR/blob/dygraph/doc/doc_en/inference_args_en.md

[UserUnknownFactor]

@shiyutang: Done.

[UserUnknownFactor]

@shiyutang: can you please cherrypick GH-10217 and GH-10216 to PaddlePaddle:dygraph and PaddlePaddle:release/2.7 if possible?

[shiyutang]

Do you have any problem doing that? I can review for you~

[UserUnknownFactor]

@shiyutang: No problem: GH-10654, GH-10655.
By the way can you please explain why is 2.7 version not based off 2.6? Is there some different approach to versioning?

[shiyutang]

2.7 is the snapshot of the dygraph branch， because we added lots of bugfix and new features on dygraph, it is easy to checkout a new branch on it.