TMQI: Tone Mapped Image Quality Index
Hojatollah
Yeganeh and Zhou Wang
Tone mapping operators
(TMOs) that convert high dynamic range (HDR) to low dynamic range (LDR) images
provide practically useful tools for the visualization of HDR images on
standard LDR displays. Different TMOs create different tone mapped images, and
a natural question is which one has the best quality. Without an appropriate
quality measure, different TMOs cannot be compared and further improvement is
directionless. Subjective rating may be a reliable evaluation method, but is
expensive and time-consuming, and more importantly, is difficult to be embedded
into optimization frameworks. Tone Mapped image Quality Index (TMQI) is an
objective quality assessment algorithm for tone mapped images by combining 1) a
multi-scale signal fidelity measure based on a modified structural similarity
(SSIM) index; and 2) a naturalness measure based on intensity statistics of
natural images. The TMQI algorithm is proposed in the following paper:
H. Yeganeh
and Z. Wang,
"Objective Quality Assessment of Tone Mapped Images," IEEE Transactions on Image
Processing, vol. 22, no. 2, pp. 657-667, Feb. 2013. [PDF]
MATLAB implementation of
the TMQI algorithm is available here. You can download it for free, change it
as you wish and use it anywhere, but please refer to its original source and
cite the above paper.
Tone
Mapped image Quality Index (TMQI)
More
useful links:
The
TMQI algorithm has been included in Francesco
Banterle’s HDR
Toobox available at MatlabCentral. The same package is also available at
the book website of Advanced HDR
Imaging.
For evaluation purpose, an
image database was created and a subjective test was conducted to compare
images generated by different tone mapping algorithms. The data set is made
available here for academic research purpose. Please cite the above paper when
using the database.
Subject-rated image database of tone-mapped
images
Below are two visual examples
of the structural fidelity maps created by TMQI and the scores computed at
multiple scales for the LDR images created from two different TMOs. Brighter indicates higher structural fidelity.
S
= 0.9152 (S1 = 0.8940; S2 = 0.9341; S3 =
0.9428; S4 = 0.9143; S5 = 0.8277)
S
= 0.8614 (S1 = 0.9161; S2 = 0.9181; S3 =
0.8958; S4 = 0.8405; S5 = 0.7041)
Created: Oct. 6, 2012
Last updated: Sept. 9, 2013