从手写图像恢复书写过程,按笔画顺序逐步重建轨迹。
Handwriting Trajectory Recovery via Autoregressive Ordered Stroke Instance Prediction

- 分两阶段:先预测有序笔画,再生成笔画内连续轨迹。
- 在中文手写数据上优于现有方法,无需轨迹简化即达最优。
- 可推广至未见汉字、英文和泰米尔文,泛化能力强。
手写轨迹恢复旨在从静态手写图像中推断隐藏的动态书写过程。由于离线手写仅保留最终的空间墨迹,书写顺序、方向及笔尖运动等时间信息丢失,导致恢复本质上具有歧义。现有学习方法常直接预测完整字符轨迹,未显式利用手写在笔画层面的组织结构。我们提出一种两阶段框架:首先恢复有序笔画实例,再重建笔画内的连续运动。第一阶段通过自回归有序笔画预测实现笔画提取与顺序恢复,并结合方向相关的结构线索辅助笔画内轨迹生成。在中文手写数据上的实验表明,所提有序预测比事后排序更有效。即使不进行轨迹简化,全点模型在数值上也优于所有对比基线;控制分析显示,轨迹采样密度显著影响评估结果。额外实验验证了对未见中文字符类别的泛化能力,以及向英文和泰米尔文手写的跨语言扩展性。
原文摘要 · Abstract (English)
Handwriting trajectory recovery aims to infer the dynamic writing process hidden behind a static handwritten image. Since offline handwriting preserves only the final spatial ink pattern, temporal information such as stroke order, writing direction, and pen-tip motion is lost, making recovery inherently ambiguous. Existing learning-based methods often directly predict the complete character trajectory without explicitly exploiting the stroke-level organization of handwriting. We argue that recovering the writing process should follow the writing process itself. Accordingly, we propose a two-stage framework that first recovers ordered stroke instances and then reconstructs continuous within-stroke motion. The first stage integrates stroke extraction and stroke-order recovery through autoregressive ordered stroke prediction, while direction-related structural cues further support within-stroke trajectory generation. Experiments on Chinese handwriting show that the proposed ordered prediction is more effective than post-hoc stroke ordering. Even without trajectory simplification, our full-point model achieves numerically better results than those reported by all compared baselines, while a controlled analysis shows that trajectory sampling density substantially affects measured recovery performance. Additional experiments demonstrate generalization to unseen Chinese character categories and cross-language extensibility to English and Tamil handwriting.
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