To meet the computational demands of the post-Moore era, neuromorphic hardware with low-power operation and multifunctional integration is highly desirable for overcoming the von Neumann bottleneck and enhancing computational efficiency. Here, we present a multifunctional optoelectronic synaptic transistor based on a MoTe₂/WS₂ heterojunction, integrating functionalities ranging from fundamental synaptic emulation to advanced visual information processing within a single device. First, under optical stimulation, the device exhibits fundamental synaptic functions such as paired-pulse facilitation, pulse-number-dependent plasticity, pulse-frequency-dependent plasticity, and experience-dependent learning, with an ultralow energy consumption of 3.29 pJ per readout event. Furthermore, the device successfully emulates the visual light adaptation behavior of the human eye. Under strong illumination, applying a negative gate voltage reduces the PSC, mimicking the contraction of the pupil under intense light to reduce incident light, thereby maintaining visual comfort and protecting the retina. Beyond this, by defining the optical pulse intensity and back-gate voltage as two independent logic inputs and the corresponding PSC as the logic output, the device enables reconfigurable logic operations that can be switched between OR and AND functions by tuning the source-drain bias. Finally, the transition from short-term plasticity to long-term plasticity of the device is exploited for image denoising. Following device-based denoising preprocessing, the recognition accuracy of the Gaussian-noise-corrupted MNIST dataset increases from an initial 72.33% to 93.27%, approaching the accuracy achieved with the raw dataset. These results highlight the potential of the device for low-power neuromorphic computing and multifunctional visual information processing.