Comments on: Colormap Test Image https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/?s_tid=feedtopost Retired from MathWorks in 2024 after 30 years of service. Can now be found at MATLAB Central, https://hornjourney.com, and https://matrixvalues.com. MathWorks career included image processing, toolbox development, MATLAB development and design, development team management, MATLAB design standards, Steve on Image Processing blog (https://blogs.mathworks.com/steve). Co-author of Digital Image Processing Using MATLAB (https://www.imageprocessingplace.com/DIPUM-3E/dipum3e_main_page.htm). French horn enthusiast, member of Concord Orchestra and Melrose Symphony, member of the board of Cormont Music and the Kendall Betts Horn Camp. Wed, 24 Aug 2022 21:01:29 +0000 hourly 1 https://wordpress.org/?v=6.2.2 By: Amir https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-29261 Mon, 23 Jul 2018 17:45:47 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-29261 It is a good Article; but I think the change was absolutely unnecessary and more destructive. Your examples make sense where you have high spacial resolution-low modulation amplitude information hidden in the image. But it absolutely destroys your understanding of the image when there is little spacial resolution information. When you need to know visually if what you are looking at is 70%, 50% or 30% you will be clueless with the new color map.
Think about the purpose of imagesc, Image scaled, Most people don’t have high spacial resolution images and if they did, they could use other scales. I think every body would agree that Jet image has 200% more contrast in 95% of the image area in your example. I don’t know why you would sacrifice better resolution in larger area to get a much lower resolution in the overall image and ok resolution in that 5% area that potentially didn’t even matter to most people. If I care about high frequency low amplitude modulations I narrow down the window and level of what I am looking at.

Thanks,

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By: Steve Eddins https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-29128 Tue, 06 Feb 2018 19:22:21 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-29128 Tito—I missed the original notification of your comment, and I just now noticed that it was still waiting in the moderation queue. I’m sorry for the extended delay.

The default MATLAB colormap changed three years ago, in the R2014b release. We made the change after a steady accumulation of evidence that convinced us that jet wasn’t the ideal for general-purpose visualization. For a more detailed explanation, see my series on the topic (part 1, part 2, part 3), as well as my annotated bibliography on the issues with rainbow colormaps..

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By: Tito https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28892 Sat, 02 Dec 2017 23:54:53 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28892 omg, another totally unnecessary change of defaults. Parula? Seriously? Looks horrible – together with font smoothing and other totally unnecessary butchering of tried and proven matlab defaults.

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By: Ross https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28871 Tue, 17 Oct 2017 14:42:41 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28871 On Kovesi’s MATLAB code page (just google it) you can download functions to create lots of different perceptually uniform color maps.

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By: Steve Eddins https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28850 Thu, 27 Jul 2017 16:22:10 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28850 Chad—Thanks for the link.

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By: Chad Greene https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28849 Wed, 26 Jul 2017 21:10:20 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28849 @Steve and Tom: The cubehelix colormaps (https://www.mathworks.com/matlabcentral/fileexchange/43700-cubehelix-colormaps–beautiful–distinct–versatile-) are perceptually monotonic (albeit not exactly perceptually linear) and provide more dynamic range than parula. Stephen Cobeldick has cleverly designed his cubehelix function to allow you to enter maximum lightness if you’re concerned about the lighter end blending in with a white background. Or you can clip the high end of any colormap a la:

col = parula(300);
colormap(col(1:256,:))

It’s worth noting that parula’s yellow can be tough to see on a white background on a computer monitor, but it’s often much more distinct when printed. Unfortunately, if you optimize for one, the other suffers.

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By: Steve Eddins https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28848 Wed, 26 Jul 2017 02:05:39 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28848 Imendo—Yes.

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By: lmendo https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28847 Tue, 25 Jul 2017 23:01:43 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28847 I think there is more saturation in the new version. This is especially noticeable in the greens, which look brighter

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By: Steve Eddins https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28845 Tue, 25 Jul 2017 16:00:09 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28845 Tom—I have seen various attempts to create a perceptually improved rainbow (jet) colormap, and I did not think any of them were very good. Using all available hues is possible and useful for some purposes, such as visualizing data with periodicity. However, using a dark-to-bright scheme for improved perceptual cues is fundamentally incompatible with using all hues.

It isn’t possible to have a one general-purpose colormap that works well for every data visualization scenario. I hope that at some point we will provide a better family of colormaps so that you have multiple choices available for your own needs.

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By: Tom https://blogs.mathworks.com/steve/2017/07/24/colormap-test-image/#comment-28844 Tue, 25 Jul 2017 14:23:49 +0000 https://blogs.mathworks.com/steve/?p=2660#comment-28844 This demonstrates well the advantages of parula vs jet.
But i still tend to use jet more often, for 2 reasons:
1. Parula highs are to bright, and it is somtimes annoying to see them on a white background.
2. Jet has more colors (thre reds), and while parula might be better for fine diffrerences, you can say that jet is more efficient in the sense that it is not “wasting” good colors.

Is it not possible to create a colormap that takes the advantages of each?

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