Controlling the color of crosshair raised by ginput

Hello, I need to use ginput. It "raises raises crosshair in the axes" - which is fine. Unfortunately, this crosshair is black, and in the axes where I need this function the background is, usually, black too, so the crosshair is very difficult to see. Changing background is not really an option. Until now I used an old version of Matlab, where this crosshair was drawn in XOR mode, and therefore this problem did not appear. Now i am forced to upgrade to the most current version, and now the XOR is banished by Mathworks. This creates problems in the described use case, but also in other use cases. Any ideas will be greatly appreciated.

Thank you,

Naum Derzhi

Answer 1

[Image Analyst]

You need to modify the built-in ginput() function since they forgot to add this incredibly obvious and needed option of color. For example see my attached code where I changed the [0,0,0] to [1,1,1] (white). Go to line 283

    crossHair(k) = uicontrol(fig, 'Style', 'text', 'Visible', 'off', 'Units', 'pixels', 'BackgroundColor', [1 1 1], 'HandleVisibility', 'off', 'HitTest', 'off'); %#ok<AGROW>

and change the color from [1,1,1] to what you want. Those are the R, G, B values in a range of 0 to 1. Then in your code, be sure to call ginputWhite instead of ginput().

You could even make a cross hair by calling plot() instead of uicontrol() and specify a dashed line if you want.

[Naum Derzhi]

Thank you very much for the idea. I gratefully accept this answer. It'll do until Mathworks restore XOR-like functionality.

[Andreea Stanescu]

Is it possible to let user choose crosshair color in an app built using GUIDE by modifing ginput function?

[Image Analyst]

Yes, have a button or pulldown menu call uisetcolor()

customColor = uisetcolor

then pass customColor into your own function my_gInput(numPoints, customColor) where you pass that input to uicontrol:

crossHair(k) = uicontrol(fig, 'Style', 'text', 'Visible', 'off', 'Units', 'pixels', 'BackgroundColor', customColor, 'HandleVisibility', 'off', 'HitTest', 'off'); %#ok<AGROW>

Be sure to copy this function and change the copy, not change the original, and use my_ginput() instead of ginput(). You don't really want to change the original function - that's not a good practice.

[Andreea Stanescu]

It worked, but what can I do for the crosshair color to update interactively as I change the colors in the modal color picker, without the need of a click for the crosshair color to update?

[Image Analyst]

You can't be in the crosshair/drawing/ginput mode simultaneously as when you're letting the user pick the color. You can't have cross hairs up while your user is clicking colors without clicking OK and then have the cross hairs change their color "live"/instantaneously as they click various color patches.

First your user picks the color with uisetcolor(), then you pass that color in to your my_ginput() as an argument.

[Seren]

Image Analyst ... U.D. Mann! Thank you.

[Palash Sarate]

it is asking for administrator permission, how did you get around that?

[Image Analyst]

You're probably trying to modify the original ginput.m in the c\program files\matlab folder. Don't do that. Make a copy of it in your MATLAB utilities folder (where you might store all your custom-written utility m-files), or your folder with all your m-files in it. Then make the change to that file.

[Daffa Faisal]

sorry but I still dont get where to place the new my_ginput file to the library

[Image Analyst]

Place it in the folder where your own, custom main m-file is, or in any other folder where you keep custom m-files (utilities) that is on your search path. Just be sure not to call it ginput.m. If you still don't understand, then tell me what folder is the m-file that you want to call ginputWhite in? Ok, put ginputWhite.m in THAT folder.

[Fenris]

Hello, how do I need to modyfiy the ginput function in order to use numPoints and customColor as input varibles, If I just add customColor and change the line to

crossHair(k) = uicontrol(fig, 'Style', 'text', 'Visible', 'off', 'Units', 'pixels', 'BackgroundColor', customColor, 'HandleVisibility', 'off', 'HitTest', 'off'); %#ok<AGROW>

and try to use my_gInput(numPoints, customColor) I get the error "input argument 'customColor' might be unused".

Thanks a Lot in advance

[Image Analyst]

Then your uicontrol statemente is probably in an if statement where it might likely never be executed.

Answer 2

[Julia]

This is an old thread, so maybe this is useless but I put it here for the benefit of people who might still have the same question. The attached version allows you to simply specify the colour you want the cross hair in as a second input argument in the shape of an RGB triplet.

[Michael]

This worked like a charm! Thank you so much!

[jiawei]

This function is very useful. Thank you very much!