Chest X-ray images are known to be extremely helpful in the investigation of a numerous pulmonary conditions such as COVID-19 and pneumonia. Many affected individuals may be protected from such pulmonary conditions through early identification. Unfortunately, COVID-19 can be misdiagnosed as pneumonia, which can rapidly worsen and lead to death. The sensitivity of RT-PCR-based COVID-19 detection is also not satisfactory. Herein, a deep-learning (DL) model for predicting three distinct classes, i.e., COVID-19, pneumonia, and normal, is presented, which achieves good classification performance. Three separate publicly available datasets and an additional dataset with their merged form were used to confirm the efficacy of the proposed model. The DL-based techniques compute features from original raw input spatial images and do not directly provide much information on extremely fine image details, which is quite important for biomedical image analysis. As the individual image bit planes (BPs) carry extremely-fine-to-coarse image information and the effective handcrafted pattern maps created from these BPs may incorporate important discriminating information, the deep features computed from such handcrafted pattern maps may provide complementary information regarding the deep features computed using raw spatial input images. Therefore, we propose a blend of deep features computed with raw spatial images and deep features computed using the proposed local bit plane-based pattern maps to predict the three classes. It is demonstrated that the blend of such features supplies improved discrimination potential and is complementary to the sole features. We incorporated multiscale information computed in each BPs along with interscale details to generate the final bit plane-based pattern maps. The proposed model achieved an average accuracy of 100%, 99.9%, 98.8%, and 98.8% for datasets 1,2, and 3 and their combined form, respectively, outperforming the existing methods.
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