CHIMERA: Adaptive CacHe Injection and SeMantic Anchor Prompting for ZERo-shot ImAge Morphing with Morphing-oriented Metrics

Abstract

Diffusion models exhibit remarkable generative ability, yet achieving smooth and semantically consistent image morphing remains a challenge. Existing approaches often yield abrupt transitions or over-saturated appearances due to the lack of adaptive structural and semantic alignments. We propose CHIMERA, a zero-shot diffusion-based framework that formulates morphing as a cached inversion–guided denoising process. To handle large semantic and appearance disparities, we propose Adaptive Cache Injection and Semantic Anchor Prompting. Adaptive Cache Injection (ACI) caches down, mid, and up blocks’ features from both inputs during DDIM inversion and re-injects them adaptively during denoising in depth- and timestep-adaptive manners, enabling natural feature fusion and smooth transitions. Semantic Anchor Prompting (SAP) leverages a vision–language model to generate a shared anchor prompt that serves as a semantic anchor, bridging dissimilar inputs and guiding the denoising process toward coherent results. Finally, we introduce the Global-Local Consistency Score (GLCS), a morphing-oriented metric that simultaneously evaluates the global harmonization of the two inputs and the smoothness of the local morphing transition. Extensive experiments and user studies show that Chimera achieves smoother and more semantically aligned transitions than existing methods, establishing a new state-of-the-art in image morphing. The code and project page will be publicly released.