Recently, diffusion models have demonstrated a remarkable ability to solve inverse problems in an unsupervised manner. Existing methods mainly focus on modifying the posterior sampling process while neglecting the potential of the forward process. In this work, we propose Shortcut Sampling for Diffusion (SSD), a novel pipeline for solving inverse problems. Instead of initiating from random noise, the key concept of SSD is to find the "Embryo", a transitional state that bridges the measurement image y and the restored image x. By utilizing the "shortcut" path of "input-Embryo-output", SSD can achieve precise and fast restoration. To obtain the Embryo in the forward process, We propose Distortion Adaptive Inversion (DA Inversion). Moreover, we apply back projection and attention injection as additional consistency constraints during the generation process. Experimentally, we demonstrate the effectiveness of SSD on several representative tasks, including super-resolution, deblurring, and colorization. Compared to state-of-the-art zero-shot methods, our method achieves competitive results with only 30 NFEs. Moreover, SSD with 100 NFEs can outperform state-of-the-art zero-shot methods in certain tasks.

提出一种名为“SSD”的新型反演流程，使用“Embryo”的概念进行前向过程，采用快捷路径，包括“输入-Embryo-输出”，在图像超分辨率、去模糊和上色等任务中实验有效性，探讨 DA 反演和反投影等一系列额外的生成一致性约束条件。与现有的 zero-shot 方法相比，只需30个NFEs就可取得竞争性的结果。

通过快捷取样加速逆问题的扩散模型