displayColorPatch

Display measured and reference color as color patches

Syntax

displayColorPatch(colorTable)

displayColorPatch(colorTable,Name,Value)

Description

displayColorPatch(colorTable) displays measured and reference colors, colorTable, for color patch regions of interest (ROIs) in a test chart. The measured color values are displayed as squares surrounded by a thick boundary of the corresponding reference color.

displayColorPatch(colorTable,Name,Value) displays measured color values with additional parameters to control aspects of the display.

Examples

Display Color Patch Diagram from ColorChecker Chart

Read an image of an X-Rite® ColorChecker® chart into the workspace.

I = imread('colorCheckerTestImage.jpg');

Create a colorChecker object, then display the chart with ROI annotations.

chart = colorChecker(I);
displayChart(chart,'displayRegistrationPoints',false)

Measure the color in each color patch ROI.

colorTable = measureColor(chart);

On a color patch diagram, display the measured and reference colors and the color error ($\Delta \mathrm{E}$).

displayColorPatch(colorTable)

Display Color Patch Diagram from Color Accuracy Measurements

This example shows how to display the color patch diagram from measurements of color accuracy on an Imatest® eSFR chart.

Read an image of an eSFR chart into the workspace.

I = imread('eSFRTestImage.jpg');

Create an esfrChart object. Display the chart, highlighting the 16 color patches.

chart = esfrChart(I);
displayChart(chart,'displayEdgeROIs',false, ...
    'displayGrayROIs',false,'displayRegistrationPoints',false)

Measure the color in all color patch ROIs.

colorTable = measureColor(chart);

Display the color accuracy measurements without the ROI index overlay. Each square color patch is the measured color, and the thick surrounding border is the reference color for that ROI. The color accuracy measurement is displayed as Delta_E, the Euclidean distance between measured and reference colors in CIE 1976 L*a*b* color space. More accurate colors have a smaller Delta_E.

displayColorPatch(colorTable,'displayROIIndex',false)

Input Arguments

colorTable — Color values

color table

Color values in each color patch, specified as an m-by-8 color table, where m is the number of patches. The eight columns represent these variables:

Variable	Description
ROI	Index of the sampled ROI. The value of ROI is an integer in the range [1, 16]. The indices match the ROI numbers displayed by displayChart.
Measured_R	Mean value of red channel pixels in an ROI. Measured_R is a scalar of the same data type as chart.Image, which can be of type single, double, uint8, or uint16.
Measured_G	Mean value of green channel pixels in an ROI. Measured_G is a scalar of the same data type as chart.Image.
Measured_B	Mean value of blue channel pixels in an ROI. Measured_B is a scalar of the same data type as chart.Image.
Reference_L	Reference L* value corresponding to the ROI. Reference_L is a scalar of type double.
Reference_a	Reference a* value corresponding to the ROI. Reference_a is a scalar of type double.
Reference_b	Reference b* value corresponding to the ROI. Reference_b is a scalar of type double.
Delta_E	Euclidean color distance between the measured and reference color values, as outlined in CIE 1976.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: displayColorPatch(myColorTable,'displayROIIndex',false) turns off the display of the ROI indices.

'displayROIIndex' — Display ROI index labels

true (default) | false

Display ROI index labels, specified as the comma-separated pair consisting of 'displayROIIndex' and true or false. When displayROIIndex is true, then displayColorPatch overlays color patch ROI index labels on the displayed color patches. The indices match the ROI numbers displayed by displayChart.

Data Types: logical

'displayDeltaE' — Display color error values

true (default) | false

Display color error ("delta E") values, specified as the comma-separated pair consisting of 'displayDeltaE' and true or false. When displayDeltaE is true, displayColorPatch overlays the color error values on the displayed color patches.

Data Types: logical

'Parent' — Axes handle of displayed image object

axes handle

Axes handle of the displayed image object, specified as the comma-separated pair consisting of 'Parent' and an axes handle. Parent specifies the parent of the image object created by displayColorPatch.

Tips

• To obtain a color table of the correct format for an esfrChart or colorChecker, use the measureColor function. You can also create your own color table containing measured and reference colors for an arbitrary number of color ROIs.

• The reference L*a*b* values of a colorTable measured from a colorChecker chart are those published by GretagMacbeth in 2005. The white point of the reference values is the CIE standard illuminant D50.