adm_csf_tools.h

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#include <math.h>
#include "common/macros.h"
 
#pragma once
 
#ifndef ADM_CSF_TOOLS_H_
#define ADM_CSF_TOOLS_H_
 
/*
 * CSF used in the DLM paper:
 * Image Quality Assessment by Separately Evaluating Detail Losses and Additive Impairments
 * Songnan Li, Fan Zhang, Lin Ma, King Ngi Ngan, IEEE Transactions on Multimedia 13(5):935-949
 */
FORCE_INLINE inline float adm_native_csf(int lambda, double adm_norm_view_dist, int adm_ref_display_height,
                                         int theta)
{
    /* This is the display visual resolution (DVR), in pixels/degree of visual angle. It should be ~56.55. */
    float r = adm_norm_view_dist * adm_ref_display_height * M_PI / 180.0;
    /* This is the nominal spatial frequency for each DWT level; first level (level = 0) is half of the DVR. */
    float spatial_frequency = r / pow(2, lambda + 1);
 
    /*
     * Oblique effect: the HVS is more sensitive to the horizontal and vertical
     * channels than the diagonal channels.
     */
    if (theta == 45) {
        spatial_frequency /= 0.7;
    }
 
    return (0.31 + 0.69 * spatial_frequency) * exp(-0.29 * spatial_frequency);
}
 
#endif /* ADM_CSF_TOOLS_H_ */