An image processing method includes: generating, from combined connected components (CCs) of a document image, candidate text CCs, candidate background CCs, and candidate natural image CCs where the candidate background CCs are excluded from the combined CCs to generate the candidate natural image CCs with a predetermined criterion dependent on the candidate text CCs; generating a final natural image bounding box by expanding a candidate natural image bounding box of the candidate natural image CCs and including in the expanded candidate natural image bounding box at least one combined CC that intersects the expanded candidate natural image bounding box; and modifying, based on the final natural image bounding box, the document image and displaying the modified document image to a user.