OCR preprocessing parameters documentation (#10447)

doc/doc_en/inference_args_en.md

 # PaddleOCR Model Inference Parameter Explanation
 
-When using PaddleOCR for model inference, you can customize the modification parameters to modify the model, data, preprocessing, postprocessing, etc.（parameter file：[utility.py](../../tools/infer/utility.py)），The detailed parameter explanation is as follows:
+When using PaddleOCR for model inference, you can customize the modification parameters to modify the model, data, preprocessing, postprocessing, etc. (parameter file: [utility.py](../../tools/infer/utility.py))，The detailed parameter explanation is as follows:
 
 * Global parameters
 
@@ -119,3 +119,12 @@ The relevant parameters of the PSE algorithm are as follows
 |  label_list | list | ['0', '180'] | The angle value corresponding to the class id |
 |  cls_batch_num | int | 6 | batch size |
 |  cls_thresh | float | 0.9 | Prediction threshold, when the model prediction result is 180 degrees, and the score is greater than the threshold, the final prediction result is considered to be 180 degrees and needs to be flipped |
+
+
+* OCR image preprocessing parameters
+
+| parameters | type | default | implication |
+| :--: | :--: | :--: | :--: |
+|  invert | bool | False | whether to invert image before processing |
+|  binarize | bool | False | whether to threshold binarize image before processing |
+|  alphacolor | tuple | "255,255,255" | Replacement color for the alpha channel, if the latter is present; R,G,B integers |