Classification of handwritten annotations in mixed-media documents

Abstract

Handwritten annotations in documents contain valuable information, but they are challenging to detect and identify. This paper addresses this challenge. We propose an al-gorithm for generating a novel mixed-media document dataset, Annotated Docset, that consists of 14 classes of machine-printed and handwritten elements and annotations. We also propose a novel loss function, Dense Loss, which can correctly identify small objects in complex documents when used in fully convolutional networks (e.g. U-NET, DeepLabV3+). Our Dense Loss function is a compound function that uses local region homogeneity to promote contiguous and smooth segmentation predictions while also using an L1-norm loss to reconstruct the dense-labelled ground truth. By using regression instead of a probabilistic approach to pixel classification, we avoid the pitfalls of training on datasets with small or underrepre-sented objects. We show that our loss function outperforms other semantic segmentation loss functions for imbalanced datasets, containing few elements that occupy small areas. Experimental results show that the proposed method achieved a mean Intersection-over-Union (mIoU) score of 0.7163 for all document classes and 0.6290 for handwritten annotations, thus outperforming state-of-the-art loss functions.