Image-adaptive 3D Lookup Tables for Real-time Image Enhancement with Bilateral Grids

Image enhancement and restoration methods using adaptive 3D lookup tables (3D LUTs) have shown promising results with real-time inferencing. These methods directly transform input pixel values into enhanced ones by using interpolation operations with predicted 3D LUT values. However, it is still challenging to deal with locally different properties of images since most 3D LUT methods are simple color-to-color transforms. Although including spatial information in this transform can be a good solution, it can significantly increase the number of parameters and inference time. To address this issue, we propose an efficient spatial-aware image enhancement model that combines bilateral grids and 3D LUTs. Specifically, we transform bilateral grids into a spatial feature domain to incorporate spatial information in our 3D LUT model. To reduce inference time and save parameters, we use slicing operations in our network architecture instead of the long decoding path of the U-Net architecture used in most existing studies. Our model achieves state-of-the-art performance without increasing parameters and further reduces inference time, as demonstrated by extensive results.