Learning Camera-Agnostic White-Balance Preferences

The image signal processor (ISP) pipeline in modern cameras consists of several modules that transform raw sensor data into visually pleasing images in a display color space. Among these, the auto white balance (AWB) module is essential for compensating for scene illumination. However, commercial AWB systems often strive to compute aesthetic white-balance preferences rather than accurate neutral color correction. While learning-based methods have improved AWB accuracy, they typically struggle to generalize across different camera sensors -- an issue for smartphones with multiple cameras. Recent work has explored cross-camera AWB, but most methods remain focused on achieving neutral white balance. In contrast, this paper is the first to address aesthetic consistency by learning a post-illuminant-estimation mapping that transforms neutral illuminant corrections into aesthetically preferred corrections in a camera-agnostic space. Once trained, our mapping can be applied after any neutral AWB module to enable consistent and stylized color rendering across unseen cameras. Our proposed model is lightweight -- containing only $\sim$500 parameters -- and runs in just 0.024 milliseconds on a typical flagship mobile CPU. Evaluated on a dataset of 771 smartphone images from three different cameras, our method achieves state-of-the-art performance while remaining fully compatible with existing cross-camera AWB techniques, introducing minimal computational and memory overhead.

Examining Joint Demosaicing and Denoising for Single-, Quad-, and Nona-Bayer Patterns

Camera sensors have color filters arranged in a mosaic layout, traditionally following the Bayer pattern. Demosaicing is a critical step camera hardware applies to obtain a full-channel RGB image. Many smartphones now have multiple sensors with different patterns, such as Quad-Bayer or Nona-Bayer. Most modern deep network-based models perform joint demosaicing and denoising with the current strategy of training a separate network per pattern. Relying on individual models per pattern requires additional memory overhead and makes it challenging to switch quickly between cameras. In this work, we are interested in analyzing strategies for joint demosaicing and denoising for the three main mosaic layouts (1x1 Single-Bayer, 2x2 Quad-Bayer, and 3x3 Nona-Bayer). We found that concatenating a three-channel mosaic embedding to the input image and training with a unified demosaicing architecture yields results that outperform existing Quad-Bayer and Nona-Bayer models and are comparable to Single-Bayer models. Additionally, we describe a maskout strategy that enhances the model performance and facilitates dead pixel correction -- a step often overlooked by existing AI-based demosaicing models. As part of this effort, we captured a new demosaicing dataset of 638 RAW images that contain challenging scenes with patches annotated for training, validation, and testing.

Time-Aware Auto White Balance in Mobile Photography

Cameras rely on auto white balance (AWB) to correct undesirable color casts caused by scene illumination and the camera's spectral sensitivity. This is typically achieved using an illuminant estimator that determines the global color cast solely from the color information in the camera's raw sensor image. Mobile devices provide valuable additional metadata-such as capture timestamp and geolocation-that offers strong contextual clues to help narrow down the possible illumination solutions. This paper proposes a lightweight illuminant estimation method that incorporates such contextual metadata, along with additional capture information and image colors, into a compact model (~5K parameters), achieving promising results, matching or surpassing larger models. To validate our method, we introduce a dataset of 3,224 smartphone images with contextual metadata collected at various times of day and under diverse lighting conditions. The dataset includes ground-truth illuminant colors, determined using a color chart, and user-preferred illuminants validated through a user study, providing a comprehensive benchmark for AWB evaluation.