Style-Preserving Generator for Synthetic License Plate Recognition

We propose the Style-Preserving Generator (SPG) to generate synthetic license plate data to train License Plate Recognition (LPR) models, and compare the performance with the same models trained on real-world data. The proposed SPG can edit the characters on real-world license plates while maintaining their original styles, allowing synthetic license plate data to be generated with user-specified characters. We can therefore synthesize license plates with desired characters to effectively alleviate the data attribute imbalance and privacy issues associated with real-world license plates. To the best of our knowledge, this work is the first study to present the making of synthetic LP data by proposing a novel text-editing approach tailor-made for LP data, that is the proposed SPG. The SPG consists of a transformer, a source encoder, a source style encoder, a character mask decoder, a target generator, and a target discriminator. Given a source license plate image and a specified text as input, these components collaborate to compute the self- and cross-attention embeddings, predict character masks, and generate a synthetic license plate in the source style but with source characters replaced by the specified characters. We adopt a two-phase training scheme. Phase 1 training uses synthetic data only, but Phase 2 training uses synthetic and real-life data. To showcase the effectiveness of the SPG, we introduce a new benchmark dataset, the LP-2025 (License Plate 2025), which alleviates the limitations of existing datasets and presents new challenges for license plate recognition and generative models. We validate SPG performance on the LP-2025 dataset and other benchmark datasets and compare it against state-of-the-art text-editing approaches.