This folder includes data for our perceptual user study. 

- interface_screenshots: We provided three screen shots of our web interface for the perceptual study. start_page includes the instructions we show to the participants. task_page1 is an example of 1 of the 12 tasks that the participant needs to complete, and task_page2 is an example where the contrast slider has been modified.

- test_images: We include all the image pairs we use in the perceptual study. The sub-folder color contains output images modified by our method; the sub-folders tonal and original contains identical input and output images, and we apply a contrast filter for the reference image in the tonal folder. We are interested in how the participants will adjust the contrast slider in order to match the color adjustment. The tonal and original cases are only used for check the validity of the responses of a participant.

- contrast_histograms: We visualize the user-selected contrast value for each image with histograms. We also performed Student's t-test with the alternative hypothesis that user will select a contrast value greater than 0. We reported both the p-value of the t-test and the mean user-selected contrast in the visualization.
