PCA-IFNNR: Principal component analysis based image fusion directed nearest neighbor representation for dark face image super resolution

Facial image captured under uncontrolled environment often degraded by blur, noise and low-light effect which significantly affect the performance of different real life applications. To solve this problem numerous face image super resolution (FISR) methods developed in last two decades. However, getting state-of-the-art accuracy for low-light face images is still a challenging task. Hence, to solve this problem a new FISR method for dark and low-resolution face images is proposed in this paper to enhance the robustness of the existing FISR techniques against darkness (low-light) problems. The proposed method tends to remove the darkness effects present in the input low-resolution (LR) face image. This method first uses the brightness enhancement approach to generate two most suitable brighter images with different brightness levels. Further, the Principal Component Analysis (PCA) based image fusion technique is developed to fuse those two images in order to generate darkness free image. After this, min-max based contrast enhancement technique is modified and applied on the fused image to make it compatible with dataset (dictionary) images for the reconstruction purpose. Further, this enhanced image is used in nearest neighbor representation to generate its equivalent brighter and high-resolution (HR) version. The simulation results using publicly accessible data sets and some real-world images imply that the proposed method outperforms existing state-of-the-art methods in darker scenarios.