refactor: allow the usage of backends in the enrich models and generalize the interface (#742)

* fix get image with cropbox

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

* allow the usage of backends in the enrich models and generalize the interface

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

* move logic in BaseTextImageEnrichmentModel

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

* renaming

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

---------

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

docs/examples/develop_formula_understanding.py

@@ -0,0 +1,88 @@
+import logging
+from pathlib import Path
+from typing import Iterable
+
+from docling_core.types.doc import DocItemLabel, DoclingDocument, NodeItem, TextItem
+
+from docling.datamodel.base_models import InputFormat, ItemAndImageEnrichmentElement
+from docling.datamodel.pipeline_options import PdfPipelineOptions
+from docling.document_converter import DocumentConverter, PdfFormatOption
+from docling.models.base_model import BaseItemAndImageEnrichmentModel
+from docling.pipeline.standard_pdf_pipeline import StandardPdfPipeline
+
+
+class ExampleFormulaUnderstandingPipelineOptions(PdfPipelineOptions):
+    do_formula_understanding: bool = True
+
+
+# A new enrichment model using both the document element and its image as input
+class ExampleFormulaUnderstandingEnrichmentModel(BaseItemAndImageEnrichmentModel):
+    images_scale = 2.6
+
+    def __init__(self, enabled: bool):
+        self.enabled = enabled
+
+    def is_processable(self, doc: DoclingDocument, element: NodeItem) -> bool:
+        return (
+            self.enabled
+            and isinstance(element, TextItem)
+            and element.label == DocItemLabel.FORMULA
+        )
+
+    def __call__(
+        self,
+        doc: DoclingDocument,
+        element_batch: Iterable[ItemAndImageEnrichmentElement],
+    ) -> Iterable[NodeItem]:
+        if not self.enabled:
+            return
+
+        for enrich_element in element_batch:
+            enrich_element.image.show()
+
+            yield enrich_element.item
+
+
+# How the pipeline can be extended.
+class ExampleFormulaUnderstandingPipeline(StandardPdfPipeline):
+
+    def __init__(self, pipeline_options: ExampleFormulaUnderstandingPipelineOptions):
+        super().__init__(pipeline_options)
+        self.pipeline_options: ExampleFormulaUnderstandingPipelineOptions
+
+        self.enrichment_pipe = [
+            ExampleFormulaUnderstandingEnrichmentModel(
+                enabled=self.pipeline_options.do_formula_understanding
+            )
+        ]
+
+        if self.pipeline_options.do_formula_understanding:
+            self.keep_backend = True
+
+    @classmethod
+    def get_default_options(cls) -> ExampleFormulaUnderstandingPipelineOptions:
+        return ExampleFormulaUnderstandingPipelineOptions()
+
+
+# Example main. In the final version, we simply have to set do_formula_understanding to true.
+def main():
+    logging.basicConfig(level=logging.INFO)
+
+    input_doc_path = Path("./tests/data/2203.01017v2.pdf")
+
+    pipeline_options = ExampleFormulaUnderstandingPipelineOptions()
+    pipeline_options.do_formula_understanding = True
+
+    doc_converter = DocumentConverter(
+        format_options={
+            InputFormat.PDF: PdfFormatOption(
+                pipeline_cls=ExampleFormulaUnderstandingPipeline,
+                pipeline_options=pipeline_options,
+            )
+        }
+    )
+    result = doc_converter.convert(input_doc_path)
+
+
+if __name__ == "__main__":
+    main()