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Color Checker Chart

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Color Checker Chart

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Synthesize a perfect version of the X-Rite Color Checker chart.

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Description

The X-Rite Color Checker Chart is a very common standard used for standardizing different images and imaging systems. (This chart has been known in the past as the Gretag Macbeth ColorChecker Chart,
and the Munsell ColorChecker Chart.) You can take a photo of one chart and a different photo at a different time or on a different system, and then develop a transformation to match the two images based on the colors of the chart's chips.

This script makes (synthesizes) a perfect X-Rite Color Checker Chart from the X-Rite supplied sRGB values. (Note: This script just creates a nice perfect image (which you can save) so it can't be used for standardizing two different images or imaging systems. It's just for looks, for example to put in a publication.) You have options on the size of the image, whether you want informational text (chip name & color) in the overlay, and whether you want to save the image.

Acknowledgements

Export Fig inspired this file.

Required Products Image Processing Toolbox
MATLAB release MATLAB 8.0 (R2012b)
Other requirements export_fig() may be used to save the image, but it is not necessary. It will run without it. It will use saveas() if you don't have export_fig().
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Comments and Ratings (6)
10 Feb 2014 Jed

Hi Image Analyst. I'm a student currently working on a project that involves detecting the presence of certain colors within images all taken under the same lighting conditions. I've been learning a lot from your Simple Hue Detection code, but am finding that I'm having trouble getting constant values for each color in different pictures (specifically dark brown, light brown, red, blue-grey, black and white). I've decided to use a color checker chart, but don't know how to fully use it to modify my images. Currently I'm using a modified method of the masks that you used for your yellow color detection that can successfully detect each color, but only for a narrow range of images. If you could, can you explain how I could use the color checker chart (a physical one) to modify the color in an image?

20 Jan 2014 John Thompson

Thanks for this helpful submission! Just what I needed.

23 Sep 2013 Image Analyst

Tim: I'm quite aware of color science. I teach color courses around the world, take color courses, and attend professional society symposia on color where I talk with top experts in the world. I'm one of the top color scientists in one of the largest corporations in the world. I develop calibrated color imaging systems full time, all the time. I think you misunderstood the intent of this submission, which was to simply create an image using the X-rite supplied values of their Color Checker chart. Nothing more. No one who images a real chart should expect to get the sRGB values. No one would be able to use this image for any calibration or anything at all other than creating a synthetic image, which is all it's meant for. I'm sorry you expected more, despite my disclaimer in the second paragraph of the description, and gave it the lowest possible rating.

14 Apr 2013 Tim Zaman

No, no, no, NO. You cannot state R,G,B values for such targets, "Image Analyst". The RGB colorspace is HIGHLY non-perceptually-uniform. Conversion to LAB would make it as perceptually uniform and standardized as you can get these days. And yes, you state that you use the sRGB values, but which sRGB whitepoint do you use? What observer degree? And so on. Convert your image to the appropriate LAB values and take the color space into consideration. Then compare LAB values.

26 Sep 2012 Malini  
26 Sep 2012 Malini

I'm really impressed with your contribution . gr8. Thanks for sharing.

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