An image processing apparatus comprising: a memory to store one or more instructions; and at least one processor (20, 30, 40, 50, 60, 70, 80, 90, 100, 230, 240) configured to execute the one or more instructions to: obtain diffusive reflection components and specular reflection components for pixels of an input image; use a high-pass filter to perform filter-processing on a diffusive reflection component image and a specular reflection component image, the diffusive reflection component image being based on the obtained diffusive reflection components and the specular reflection component image being based on the obtained specular reflection components, and use the high-pass filter to perform filter-processing on the input image; combine the filter-processed diffusive reflection component image and the filter-processed specular reflection component image to generate a combined image; and evaluate a separation accuracy of the diffusive reflection components and the specular reflection components based on the combined image and the filter-processed input image; and determine whether to modify at least one of a diffusive reflection component and a specular reflection component of at least one pixel based on a result of evaluation of the separation accuracy. a memory to store one or more instructions; and at least one processor (20, 30, 40, 50, 60, 70, 80, 90, 100, 230, 240) configured to execute the one or more instructions to: obtain diffusive reflection components and specular reflection components for pixels of an input image; use a high-pass filter to perform filter-processing on a diffusive reflection component image and a specular reflection component image, the diffusive reflection component image being based on the obtained diffusive reflection components and the specular reflection component image being based on the obtained specular reflection components, and use the high-pass filter to perform filter-processing on the input image; combine the filter-processed diffusive reflection component image and the filter-processed specular reflection component image to generate a combined image; and evaluate a separation accuracy of the diffusive reflection components and the specular reflection components based on the combined image and the filter-processed input image; and determine whether to modify at least one of a diffusive reflection component and a specular reflection component of at least one pixel based on a result of evaluation of the separation accuracy. obtain diffusive reflection components and specular reflection components for pixels of an input image; use a high-pass filter to perform filter-processing on a diffusive reflection component image and a specular reflection component image, the diffusive reflection component image being based on the obtained diffusive reflection components and the specular reflection component image being based on the obtained specular reflection components, and use the high-pass filter to perform filter-processing on the input image; combine the filter-processed diffusive reflection component image and the filter-processed specular reflection component image to generate a combined image; and evaluate a separation accuracy of the diffusive reflection components and the specular reflection components based on the combined image and the filter-processed input image; and determine whether to modify at least one of a diffusive reflection component and a specular reflection component of at least one pixel based on a result of evaluation of the separation accuracy.