Comments on: A Lab-based uniform color scale http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/ Steve Eddins manages the Image & Geospatial development team at <a href="http://www.mathworks.com/">The MathWorks</a> and coauthored <a href="http://www.mathworks.com/support/books/book5291.html?category=-1&language=-1">Digital Image Processing Using MATLAB</a>. He writes here about image processing concepts, algorithm implementations, and MATLAB.<br><br><img> Mon, 23 Nov 2009 01:32:16 +0000 http://wordpress.org/?v=2.3.1 By: Malcolm http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-22160 Malcolm Thu, 24 Sep 2009 18:30:21 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-22160 It's single figure with two filled contour plots placed using subplot. I'll take a look at CLim and see what I can do with that. Thanks for the heads up it's appreciated. -M It’s single figure with two filled contour plots placed using subplot. I’ll take a look at CLim and see what I can do with that. Thanks for the heads up it’s appreciated.

-M

]]> By: Steve http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-22157 Steve Thu, 24 Sep 2009 11:36:50 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-22157 Malcolm—I'm not sure exactly how you are displaying the various pieces together (one figure? multiple figures? subplots?), but you might try explicitly setting the CLim property of the axes objects involved. Malcolm—I’m not sure exactly how you are displaying the various pieces together (one figure? multiple figures? subplots?), but you might try explicitly setting the CLim property of the axes objects involved.

]]> By: Malcolm http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-22155 Malcolm Wed, 23 Sep 2009 20:56:56 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-22155 Hi Steve- Not exactly on topic, but you seem like the man in the know! I have two contour plots, one with range 0-10 and the other with range 0-5. When applying the colormap it is scaled to fit the data range, but when displaying the images next to each other I want them to share the same scale, so that like colour contours match up. Is there an easy way to achieve this without messing around with the original data for the plots? Thanks in advance, -M Hi Steve-

Not exactly on topic, but you seem like the man in the know!

I have two contour plots, one with range 0-10 and the other with range 0-5. When applying the colormap it is scaled to fit the data range, but when displaying the images next to each other I want them to share the same scale, so that like colour contours match up. Is there an easy way to achieve this without messing around with the original data for the plots?

Thanks in advance,

-M

]]> By: Steve http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21931 Steve Wed, 01 Jul 2009 17:40:39 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21931 Ernest—Look at setting the FaceColor property. The code for setting that is shown on the <a href="http://blogs.mathworks.com/steve/2006/11/24/tetrahedral-interpolation-for-colorspace-conversion/" rel="nofollow">page you asked about</a>. Ernest—Look at setting the FaceColor property. The code for setting that is shown on the page you asked about.

]]> By: Ernest Miller http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21930 Ernest Miller Wed, 01 Jul 2009 17:27:50 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21930 Hi Steve, Understood. However, can you explain how to change the colors? Thanks, Ernest Hi Steve,

Understood. However, can you explain how to change the colors?

Thanks,

Ernest

]]> By: Steve http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21902 Steve Sun, 21 Jun 2009 23:55:47 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21902 Ernest—The plots are simply showing faces of a tetrahedra. The colors I chose to display the faces with don't have anything to do "real" colors. Ernest—The plots are simply showing faces of a tetrahedra. The colors I chose to display the faces with don’t have anything to do “real” colors.

]]> By: Ernest Miller http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21900 Ernest Miller Sat, 20 Jun 2009 00:02:54 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21900 Hello Steve, Regarding tetrahedral interpolation for color space conversion (Nov 24, 2006) you explain that the view is hard to see, so you show individual tetrahedra in separate plots. Can you explain how the individual plots can represent more accurate RGBCMY colors. I changed 'jet' to 'prism' and that was much closer, but I can not tell if the color order is correct nor how to adjust each fill color closer to actual color. Appreciate your help. Ernest Hello Steve,

Regarding tetrahedral interpolation for color space conversion (Nov 24, 2006) you explain that the view is hard to see, so you show individual tetrahedra in separate plots.

Can you explain how the individual plots can represent more accurate RGBCMY colors. I changed ‘jet’ to ‘prism’ and that was much closer, but I can not tell if the color order is correct nor how to adjust each fill color closer to actual color.

Appreciate your help.

Ernest

]]> By: Ernest Miller http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21879 Ernest Miller Tue, 16 Jun 2009 17:35:48 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21879 Doug, Thank you for the response. Much appreciated! Former Kodaker's seem to be good fellows. Ernest Doug,

Thank you for the response. Much appreciated!

Former Kodaker’s seem to be good fellows.

Ernest

]]> By: Steve http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21805 Steve Fri, 29 May 2009 12:06:14 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21805 Doug—Thanks for jumping in! Doug—Thanks for jumping in!

]]> By: Doug Schwarz http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21804 Doug Schwarz Thu, 28 May 2009 18:15:47 +0000 http://blogs.mathworks.com/steve/2006/05/09/a-lab-based-uniform-color-scale/#comment-21804 Ernest, It's easy to compute the volume in Lab space of a set of Lab colors with convhulln. Just pass in the nx3 matrix of Lab coordinates and the volume is the second output argument. However, you have to be careful about what you are comparing. It is not necessarily true that a color that is inside the convex hull is physically realizable with the system that is producing the colors (which is just another way of saying that the gamut is not convex). In that case the volume of the hull is a poor indication of the true gamut. That may be why applications vary -- they are designed for use with different color systems. Doug (former Kodaker) Ernest,

It’s easy to compute the volume in Lab space of a set of Lab colors with convhulln. Just pass in the nx3 matrix of Lab coordinates and the volume is the second output argument. However, you have to be careful about what you are comparing. It is not necessarily true that a color that is inside the convex hull is physically realizable with the system that is producing the colors (which is just another way of saying that the gamut is not convex). In that case the volume of the hull is a poor indication of the true gamut. That may be why applications vary — they are designed for use with different color systems.

Doug (former Kodaker)

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