Text image machine translation (TIMT) aims at directly translating text in the source language embedded in images into the target language. Most existing systems follow the cascaded pipeline diagram from recognition to translation, which suffers from the problem of error propagation, parameter redundancy, and information reduction. The end-to-end model has the potential to alleviate these issues via bridging the recognition and translation models. However, the challenge is the data limitation and modality gap between text and image. In this paper, we propose a novel end-to-end model, namely Modal contrastive learning based End-to-end Text Image Machine Translation (METIMT), which alleviates these issues through end-to-end text image machine translation architecture and modal contrastive learning. Specifically, an image encoder is designed to encode images into the same feature space of corresponding text sentences, with the guidance of an intramodal and inter-modal contrastive learning module. To further promote the research of text image machine translation, we have constructed one synthetic and two real-world datasets. Extensive experiments show that our lighter, faster model outperforms not only existing pipeline methods but also state-of-the-art end-to-end models on both synthetic and real-world evaluation sets. Our code and dataset will be released to the public.

End-to-end text image translation (TIT), which aims at translating the source language embedded in images to the target language, has attracted intensive attention in recent research. However, data sparsity limits the performance of end-to-end text image translation. Multi-task learning is a nontrivial way to alleviate this problem via exploring knowledge from complementary related tasks. In this paper, we propose a novel text translation enhanced text image translation, which trains the end-to-end model with text translation as an auxiliary task. By sharing model parameters and multi-task training, our model is able to take full advantage of easily-available large-scale text parallel corpus. Extensive experimental results show our proposed method outperforms existing end-to-end methods, and the joint multi-task learning with both text translation and recognition tasks achieves better results, proving translation and recognition auxiliary tasks are complementary.1