Generative adversarial networks for handwriting image generation: a review

Handwriting synthesis, the task of automatically generating realistic images of handwritten text, has gained increasing attention in recent years, both as a challenge in itself, as well as a task that supports handwriting recognition research. The latter task is to synthesize large image datasets that can then be used to train deep learning models to recognize handwritten text without the need for human-provided annotations. While early attempts at developing handwriting generators yielded limited results [1], more recent works involving generative models of deep neural network architectures have been shown able to produce realistic imitations of human handwriting [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]. In this review, we focus on one of the most prevalent and successful architectures in the field of handwriting synthesis, the generative adversarial network (GAN). We describe the capabilities, architecture specifics, and performance of the GAN-based models that have been introduced to the literature since 2019 [2,3,4,5,6,7,8,9,10,11,12,13,14]. These models can generate random handwriting styles, imitate reference styles, and produce realistic images of arbitrary text that was not in the training lexicon. The generated images have been shown to contribute to improving handwriting recognition results when augmenting the training samples of recognition models with synthetic images. The synthetic images were often hard to expose as non-real, even by human examiners, but also could be implausible or style-limited. The review includes a discussion of the characteristics of the GAN architecture in comparison with other paradigms in the image-generation domain and highlights the remaining challenges for handwriting synthesis.