This paper presents a miniaturized spectrometer that utilizes a single SnS₂/ReSe₂ van der Waals (vdW) heterostructure to achieve photodetection, spectrum reconstruction, spectral imaging, and long-term image memory. The device has a footprint of 19 μm, a bandwidth from 400 to 800 nm, a spectral resolution of 5 nm, and a >10⁶ s long-term image memory. The photogating effect and non-volatile optoelectronic memory are induced by interface trap states, which allow for gate-tunable and wavelength-dependent photogating. The spectrometer's capabilities are demonstrated through spectrum reconstruction, spectral imaging, and neuromorphic computing, showing its potential for applications in portable optoelectronics, wearable sensors, artificial synapses, neural networks, machine vision, and imaging processing. The approach represents a significant step beyond von Neumann architectures, offering a single-detector computational spectrometer with high performance and reduced energy consumption.This paper presents a miniaturized spectrometer that utilizes a single SnS₂/ReSe₂ van der Waals (vdW) heterostructure to achieve photodetection, spectrum reconstruction, spectral imaging, and long-term image memory. The device has a footprint of 19 μm, a bandwidth from 400 to 800 nm, a spectral resolution of 5 nm, and a >10⁶ s long-term image memory. The photogating effect and non-volatile optoelectronic memory are induced by interface trap states, which allow for gate-tunable and wavelength-dependent photogating. The spectrometer's capabilities are demonstrated through spectrum reconstruction, spectral imaging, and neuromorphic computing, showing its potential for applications in portable optoelectronics, wearable sensors, artificial synapses, neural networks, machine vision, and imaging processing. The approach represents a significant step beyond von Neumann architectures, offering a single-detector computational spectrometer with high performance and reduced energy consumption.