One of my consulting clients recently asked me if I knew any builtin Matlab GUI control that could display a list of colormap names ^[1] alongside their respective image icons, in a listbox or popup menu (drop-down/combo-box):

 

parula

imageFilename = [docroot, '/matlab/ref/colormap_parula.png']

Note that for a local image to be accepted by HTML, it needs to follow certain conventions. In our case, the HTML string for displaying the above image is:

parula

Warning: it’s easy when dealing with HTML images in Matlab to get the format confused, resulting in a red-x icon. I discussed this issue ^[4] some 4 years ago, which is still relevant.

How can we get the list of available builtin colormaps? The standard Matlab way of doing this would be something like this:

>> possibleColormaps = set(gcf,'Colormap')
possibleColormaps =
     {}

but as we can see, for some unknown reason (probably another MathWorks omission), Matlab does not list the names of its available builtin colormaps.
Fortunately, all the builtin colormaps have image filenames that follow the same convention, which make it easy to get this list by simply listing the names of the relevant files, from which we can easily create the necessary HTML strings:

>> iconFiles = dir([docroot, '/matlab/ref/colormap_*.png']);
>> colormapNames = regexprep({iconFiles.name}, '.*_(.*).png', '$1')
colormapNames =
  Columns 1 through 9
    'autumn'    'bone'    'colorcube'    'cool'    'copper'    'flag'    'gray'    'hot'    'hsv'
  Columns 10 through 18
    'jet'    'lines'    'parula'    'pink'    'prism'    'spring'    'summer'    'white'    'winter'
>> htmlStrings = strcat('', colormapNames')
str =
    'autumn'
    'bone'
    'colorcube'
    ...
>> hListbox = uicontrol(gcf, 'Style','listbox', 'Units','pixel', 'Pos',[10,10,270,200], 'String',htmlStrings);
>> hPopup   = uicontrol(gcf, 'Style','popup',   'Units','pixel', 'Pos',[10,500,270,20], 'String',htmlStrings);

…which results in the screenshots at the top of this post.
Note how I scaled the images to 10px high (so that the labels would be shown and not cropped vertically) and 200px wide (so that it becomes narrower than the default 434px). There’s really no need in this case for the full 434×27 image size – such flat images scale very nicely, even when their aspect ratio is not preserved. You can adjust the height and width values for a best fit with you GUI.
Unfortunately, it seems that HTML strings are not supported in the new web-based uifigure controls. This is not really Matlab’s fault because the way to customize labels in HTML controls is via CSS: directly embedding HTML code in labels does not work (it’s a Java-Swing feature, not a browser feature). I really hope that either HTML or CSS processing will be enabled for web-based uicontrol in a future Matlab release, because until that time uifigure uicontrols will remain seriously deficient compared to standard figure uicontrols. Until then, if we must use uifigures and wish to customize our labels or listbox items, we can directly access the underlying web controls, as Iliya explained here ^[5].

A blog reader recently complained ^[6] that I’m abusing Swing and basically making Matlab work in unnatural ways, “something it was never meant to be“. I feel that using HTML as I’ve shown last week and in this post would fall under the same category in his eyes. To him and to others who complain I say that I have absolutely no remorse about doing this. When I purchase anything I have the full rights (within the scope of the license) to adapt it in whatever way fits my needs. As a software developer and manager for over 25 years, I’ve developed in dozens of programming languages and environments, and I still enjoy [ab]using Matlab. Matlab is a great environment to get things done quickly and if this sometimes requires a bit of HTML or Java hacks that make some people cringe, then that’s their problem, not mine – I’m content with being able to do in Matlab [nearly] everything I want, quickly, and move on to the next project. As long as it gets the job done, that’s fine by me. If this makes me more of an engineer than a computer scientist, then so be it.
On the flip side, I say to those who claim that Matlab is lacking in this or that aspect, that in most likelihood the limitation is only in their minds, not in Matlab – we can do amazing stuff with Matlab if we just open our minds, and possibly use some undocumented hacks. I’m not saying that Matlab has no limitations, I’m just saying that in most cases they can be overcome if we took the time and trouble to look for a solution. Matlab is a great tool and yet many people are not aware of its potential. Blaming Matlab for its failings is just an easy excuse in many cases. Of course, MathWorks could help my crusade on this subject by enabling useful features such as easy GUI component customizations…
On this sad day, I wish you all Shanah Tova!

6 Comments To "Icon images & text in Matlab uicontrols"

#1 Comment By Royi On September 28, 2016 @ 16:31

#2 Comment By Aurélien QUEFFURUST On September 29, 2016 @ 10:42

r = loadjson('functionSignatures.json')
choices = r.colormap.inputs{1,2}.type{1,1}{1}

choices = {'parula','jet','hsv','hot','cool','spring','summer','autumn','winter','gray','bone','copper','pink','lines','colorcube','prism','flag','white','default'}

#3 Comment By Matt On September 30, 2016 @ 13:28

#4 Comment By Yair Altman On September 30, 2016 @ 13:50

#5 Comment By Aurélien QUEFFURUST On October 3, 2016 @ 10:26

#6 Comment By Ozgu On June 25, 2019 @ 20:57