How to create a bounding box in webcam preview and capture image in that bounding box?
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Explorer
am 4 Feb. 2014
Kommentiert: Image Analyst
am 15 Mai 2020
This is how I want to do it:
1. Determine positions in webcam preview
2. Create bounding box on that positions in webcam preview
3. Place hand in bounding box
4. Capture it
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Image Analyst
am 4 Feb. 2014
You can use ginput, rectangle(), imrect() or other functions to determine locations in the image. Then use plot() to create the box. Then call getsnapshot, which will get the full image but you then crop it with imcrop() to limit it to just the bounding box.
18 Kommentare
Image Analyst
am 6 Mai 2020
Did you install the webcam add-on? See the Add-ons tab. Home->Addons-> Get Addons -> MATLAB support package for USB webcams.
What does this show:
webcamlist % No semicolons.
mycam=webcam
Heloise BOTREL
am 7 Mai 2020
Ans :
webcamlist % No semicolons.
mycam=webcam
ans =
1×1 cell array
{'HP TrueVision HD'}
mycam =
webcam with properties:
Name: 'HP TrueVision HD'
AvailableResolutions: {1×6 cell}
Resolution: '640x480'
Exposure: -6
Sharpness: 2
Gain: 4
Contrast: 32
WhiteBalance: 4000
Saturation: 64
Hue: 0
Gamma: 120
ExposureMode: 'auto'
Brightness: 128
BacklightCompensation: 1
WhiteBalanceMode: 'auto'
I have this package and "Image Acquisition Toolbox Support Package for OS generic Video Interface" and 'Image Acquisition Toolbox"
Weitere Antworten (2)
Aude Menet
am 14 Mai 2020
Bearbeitet: Aude Menet
am 14 Mai 2020
Error using videoinpu (line 219)
Invalid ADAPTATORNAME specified. Type 'imaqhwinfo' for a list of available
ADAPTORNAMEs. Image acquisition adaptors may be available as downloadable
support packages. Open Add-Ons Explorer to install additional adaptors.
Error in cameratest (line 20)
videoObject=videoinput('winvideo');
Can someone help me to fix these errors please ?
4 Kommentare
Image Analyst
am 15 Mai 2020
Have you downloaded the webcam add on? Use the Add-Ons explorer from the Home tab of the tool ribbon and type in webcam.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/293102/image.png)
Aude Menet
am 15 Mai 2020
Yes I have dowloaded them since I'm trying to make my webcam work through matlab.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/293158/image.png)
Image Analyst
am 15 Mai 2020
When you do this, do you get a live video window that pops up? I do
webcamlist
mycam = webcam
methods(mycam)
mycam.preview
2 Kommentare
Image Analyst
am 15 Mai 2020
Now try the snapshot() method:
% Display a list of installed cameras.
webcamlist
% Get an object linked to the webcam.
mycam = webcam
% Show what things this camera can do
methods(mycam)
properties(mycam)
% Open live video window.
mycam.preview
% Prompt user to snap a photo.
promptMessage = sprintf('Do you want to snap a photo,\nor Quit?');
titleBarCaption = 'Continue?';
buttonText = questdlg(promptMessage, titleBarCaption, 'Snap', 'Quit', 'Snap');
if contains(buttonText, 'Quit', 'IgnoreCase', true)
return;
end
% Snap the photo.
rgbImage = mycam.snapshot;
% Close live video window.
mycam.closePreview
% Display image
imshow(rgbImage);
caption = sprintf('Here is the photo you snapped at %s', datestr(now));
title(caption, 'FontSize', 20);
% Maximize figure.
g = gcf;
g.WindowState = 'maximized';
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