TMQI: Tone Mapped Image Quality Index
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:
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.
More useful links:
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.
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