MTBWD: Multidirectional Two-Step Bisection Weighting Demosaicking for Image Sensors

This article proposes a multidirectional two-step bisection weighting demosaicking (MTBWD) method for the image sensors. For image demosaicking, complicated operations are typically employed to calculate more precise weights and reconstructed pixel values. Considering hardware implementation, we tend to avoid using complicated operations, such as multiplication; therefore, bisection weighting is proposed, implying that all interpolated weights are designed to be the fraction with a value of denominator that is a power of 2; however, if we use only the bisection weighting, it is challenging to adopt the multidirectional information. We, therefore, proposed two-step bisection weighting. In the first step, we compute the global directional information through the first bisection weighting of local directional information, consisting of variations and color difference values of cardinal and oblique directions. Then, the final color difference value is computed through the second-time bisection weighting of global directional information to interpolate the missing pixel. To reduce hardware cost, under the limitation of avoiding multiplication, MTBWD could still use multidirectional information to achieve competitive image quality. The very large-scale integration (VLSI) architecture of MTBWD is implemented and synthesized using TSMC 40-nm technology. Experimentally, compared with the related low-cost methods, the proposed MTBWD achieves the best average quality for diverse images, including images in Kodak24, IMAX, and DIV2K datasets and some photographs captured in a specific scene. The hardware reports confirm that the MTBWD is the most cost-effective in the current low-cost demosaicking studies with similar hardware costs.