refactor(mfr): optimize image processing in Unimernet

- Remove unnecessary __getitem__ method
- Simplify image cropping in detect_math_formula_region
- Improve code readability and efficiency

magic_pdf/model/sub_modules/mfr/unimernet/Unimernet.py

@@ -18,16 +18,6 @@ class MathDataset(Dataset):
     def __len__(self):
         return len(self.image_paths)
 
-    def __getitem__(self, idx):
-        # if not pil image, then convert to pil image
-        if isinstance(self.image_paths[idx], str):
-            raw_image = Image.open(self.image_paths[idx])
-        else:
-            raw_image = self.image_paths[idx]
-        if self.transform:
-            image = self.transform(raw_image)
-            return image
-
 
 def latex_rm_whitespace(s: str):
     """Remove unnecessary whitespace from LaTeX code."""
@@ -83,8 +73,7 @@ class UnimernetModel(object):
                 "latex": "",
             }
             formula_list.append(new_item)
-            pil_img = Image.fromarray(image)
-            bbox_img = pil_img.crop((xmin, ymin, xmax, ymax))
+            bbox_img = image[ymin:ymax, xmin:xmax]
             mf_image_list.append(bbox_img)
 
         dataset = MathDataset(mf_image_list, transform=self.mfr_transform)
@@ -99,7 +88,6 @@ class UnimernetModel(object):
             res["latex"] = latex_rm_whitespace(latex)
         return formula_list
 
-
     def batch_predict(self, images_mfd_res: list, images: list, batch_size: int = 64) -> list:
         images_formula_list = []
         mf_image_list = []