Offline handwritten text recognition from images is an important problem for enterprises attempting to digitize large volumes of handmarked scanned documents/reports. Deep recurrent models such as Multi-dimensional LSTMs have been shown to yield superior performance over traditional Hidden Markov Model based approaches that suffer from the Markov assumption and therefore lack the representational power of RNNs. In this paper we introduce a novel approach that combines a deep convolutional network with a recurrent Encoder-Decoder network to map an image to a sequence of characters corresponding to the text present in the image. The entire model is trained end-to-end using Focal Loss, an improvement over the standard Cross-Entropy loss that addresses the class imbalance problem, inherent to text recognition. To enhance the decoding capacity of the model, Beam Search algorithm is employed which searches for the best sequence out of a set of hypotheses based on a joint distribution of individual characters. Our model takes as input a downsampled version of the original image thereby making it both computationally and memory efficient. The experimental results were benchmarked against two publicly available datasets, IAM and RIMES. We surpass the state-of-the-art word level accuracy on the evaluation set of both datasets by 3.5% & 1.1%, respectively.

本文提出一种将卷积神经网络和序列到序列模型相结合，将图像映射到文本序列，实现手写文本识别能力，且采用Focal Loss方法解决文本识别的类别不平衡问题，并应用Beam Search算法来提升模型的解码性能，在常见的IAM和RIMES数据集上实验表明，本文提出的模型在词级别的准确率方面分别提高了3.5％和1.1％，达到了国际先进水平。

一种高效的端到端神经模型用于手写文本识别