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Python: match the MATLAB MSSIM formula in Measure_Quality #783

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AnderBiguri merged 1 commit into from
Sep 29, 2026
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Python: match the MATLAB MSSIM formula in Measure_Quality #783

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14 changes: 8 additions & 6 deletions Python/tigre/utilities/Measure_Quality.py
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Original file line number Diff line number Diff line change
Expand Up @@ -64,22 +64,24 @@ def Measure_Quality(res_prev, res, QualMeasOpts): # noqa: N803
K1 = 0.01 # K1 is a small constant <<1
d = np.max(res_prev) - np.min(res_prev) # dynamic range of the pixel values
l = ((2 * mean_res * mean_res_p) + (K1 * d) ** 2) / (
(mean_res_p ** 2) + (mean_res ** 2) + K1 * d ** 2
(mean_res_p ** 2) + (mean_res ** 2) + (K1 * d) ** 2
)

# Contrast comparison

K2 = 0.02
sres_p = res_prev.std()
sres = res.std()
K2 = 0.03
sres_p = res_prev.std(ddof=1)
sres = res.std(ddof=1)

c = ((2 * sres_p * sres) + (K2 * d) ** 2) / ((sres_p ** 2) + (sres ** 2) + K2 * d ** 2)
c = ((2 * sres_p * sres) + (K2 * d) ** 2) / (
(sres_p ** 2) + (sres ** 2) + (K2 * d) ** 2
)

# Structure comparison
diffres_p = res_prev - mean_res_p
diffres = res - mean_res
delta = (1 / (N - 1)) * np.sum(diffres_p * diffres)
s = (delta + (((K2 * d) ** 2)) / 2) / ((sres_p * sres) + ((K2 * d ** 2) / 2))
s = (delta + (((K2 * d) ** 2)) / 2) / ((sres_p * sres) + (((K2 * d) ** 2) / 2))

values.append((1 / N) * l * c * s)
if "UQI" == qual:
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