Fig 1.
Example of a misleading colormap.
Comparison between different colormaps overlaid onto the test image by Kovesi and a nanoscale secondary ion mass spectrometry image. Colormaps are as follows: (a) perceptually uniform grayscale, (b) jet, (c) jet as it appears to someone with red-green colorblindness, and (d) viridis [1], the current gold standard colormap. Below each NanoSIMS image is a corresponding “colormap-data perceptual sensitivity” (CDPS) plot, which compares perceptual differences of the colormap to actual, underlying data differences. m is the slope of the fitted line and r2 is the coefficient of determination calculated using a simple linear regression. An example of how the data may be misinterpreted are evident in the bright yellow spots in (b) and (c), which appear to represent significantly higher values than the surrounding regions. However, in fact, the dark red (in b) and dark yellow (in c) actually represent the highest values. For someone who is red-green colorblind, this is made even more difficult to interpret due to the broad, bright band in the center of the colormap with values that are difficult to distinguish.
Fig 2.
CVD-safe colorspace in CIECAM02-UCS.
Visual of how limited color vision is for those with CVD. (a) 2D-representation of area of colorspace accessible to those without (black) and with (gray) complete red-green colorblindness as a function of the CIECAM02-UCS parameters (J′, a′, and b′). (b) Fraction of sRGB colors visible as a function of deuteranomaly severity. A severity of 0 corresponds to normal color vision whereas a severity of 100 corresponds to complete dichromacy (i.e. red-green colorblindness in this case).
Fig 3.
Schematic of our script and how it optimizes colormaps for CVD. The colorspace, either sRGB or CIECAM02-UCS, where each operation takes place is shown along with the Python packages specifically required for each step.
Fig 4.
Colormap adjustment iterations.
In this example, the viridis colormap is taken through each stage of our pipeline. From top to bottom, the image plotted is the colormap (i) as it was input, (ii) overlaid on the test image discussed by Peter Kovesi [21], and (iii-v) based on the method presented by the Smith group [1], these show the values of this colormap in CIECAM02-UCS space, with (iii) comparing individual values J′ (black), a′ (blue), and b′ (red) across the map, (iv) showing the perceptual deltas between each point on the map, calculated as the Euclidean distance between each point, and (v) providing a three dimensional view of the colormap in this space.
Fig 5.
Our optimal colormap, cividis.
Colormap shown overlaid onto a a) NanoSIMS image and b) fluid velocity map from COMSOL. Below is each corresponding CDPS plot for data along the white lines.