Hi Kyle,
I understand you're working in MATLAB App Designer (R2020b) to implement a pixel coordinate picker on a 'UIAxes', which is enabled only when a switch is turned "On".
The current approach utilizes 'drawpoint' to capture clicks, which are not entirely stable, particularly with point deletion and figure responsiveness.
To make this interaction more reliable, you can use the 'ButtonDownFcn' callback on the image object rather than relying on 'drawpoint' which is more optimized towards freehand ROI workflows. This approach gives you more direct control and integrates smoothly with an On/Off switch.
Here is a pattern you can try incorporating in the existing App Designer code:
- Loading and displaying the image with 'ButtonDownFcn' callback:
% Example in startupFcn or image display function
imgHandle = imshow(yourImageData, 'Parent', app.UIAxes);
imgHandle.ButtonDownFcn = @(src, event) imageClickCallback(app, src, event);
- Creating a separate function in the 'imageClickCallback' method:
function imageClickCallback(app, src, event)
if strcmp(app.ToggleSwitch.Value, 'On')
cp = app.UIAxes.CurrentPoint;
x = round(cp(1,1));
y = round(cp(1,2));
% Use x, y for further processing
disp(['Selected pixel: (' num2str(x) ', ' num2str(y) ')']);
end
end
This method checks whether the switch is "On" and then captures the click location from the 'CurrentPoint' of the UIAxes. It avoids the overhead of 'drawpoint' and gives consistent results with pixel selection.
- Ensure that the image or axes has 'PickableParts' set to 'all' and 'HitTest' set to 'on', which is true by default when using 'imshow'.
- If you are layering other elements on the axes, ensure that the image remains the bottom layer and is receiving clicks.
To know more about the usage of various functions and parameters used in the above-mentioned code snippets, you can refer to the following documentation links:
- 'imshow' function: https://www.mathworks.com/help/images/ref/imshow.html
- 'CurrentPoint' property:https://www.mathworks.com/help/matlab/ref/matlab.graphics.axis.axes-properties.html#btwpyy7-1_sep_shared-CurrentPoint:~:text=CurrentPoint%20%E2%80%94%20Location%20of%20mouse%20pointer%0ARead%2Donly%3A%202%2Dby%2D3%20array
Hope this helps!
