Is there any way to constraint the the imline to be always perpendicular to the other imline drawn on the same object. for ex. I draw a first line using "imline" now I want to draw second line across the first line to be perpendicular to it. if there is a way to force the second imline to be perpendicular to the first line keeping the flexibility of extending the length it will solve my problem some extent.
I want something like a flexible cross hair(which can rotate along the axis and have flexible sides) on my image to measure the height and width of the certain object.
Code:
function perpline()
imshow(rand(200),[]);
line1 = imline(gca,[50 50; 150 150]);
setColor(line1,'r');
line2 = imline(gca,[50 150; 150 50]);
setColor(line2,'g');
addNewPositionCallback(line2,#(pos)callback_line(pos));
function callback_line(pos)
% Must update line1 based on line2's position
pos_line1 = getPosition(line1);
pos_line2 = getPosition(line2);
% Get middle
pos_center = [(pos_line2(1,1)+pos_line2(2,1))/2 (pos_line2(1,2)+pos_line2(2,2))/2];
% Find displacement
vec_disp = [pos_line2(2,1)-pos_line2(1,1) pos_line2(2,2)-pos_line2(1,2)];
% Get normal unit vector
vec_perp = [-vec_disp(2) vec_disp(1)]/norm(vec_disp);
% Preserve length of line2
length_line1 = norm([pos_line1(2,1)-pos_line1(1,1) pos_line1(2,2)-pos_line1(1,2)]);
pos_line1_update = [-vec_perp*length_line1/2+pos_center;
vec_perp*length_line1/2+pos_center];
% Set position
setPosition(line1,pos_line1_update);
end
end
Save it as a function then call it. You can drag the green line around and the red line remains perpendicular. Note that you have to define how you want it to preserve the perpendicularity. I chose to preserve the length of the red line and keep it in the center of the green line.
Related
Consider the simple code below that generates a straight downward sloping line in MATLAB.
clear, clc, close all
t = 0:0.1:1;
y = -t+1;
plot(t,y)
ax = gca
This is a line with slope -1, so the (acute) angle between the horizontal axis and the line is 45 degrees. Except it isn't when you measure with a protractor on your monitor.
Without changing the range of values displayed on the x and y axes or the height of the figure window, how could I ensure I would measure 45 degrees from the horizontal axis to the line if I held a protractor up to the screen?
My current approach is to change the width of the figure window. In the limit as the figure window is infinitely thin, the line x is a vertical line. Conversely, if the figure window is stretched to the edges of a monitor, it flattens out. Somewhere in the middle, the line has the angle I want. I just can't find a good way to mathematically find this point and instantiate it in code.
Edit: A slightly more generic solution for any acute angle. (I didn't test obtuse angles.)
clear, clc, close all
ang_deg = 70;
slope = tand(ang_deg);
t = 0:0.1:1;
y = -slope*t+1;
f = figure;
f.Position(3) = f.Position(3)*1.5;
plot(t,y)
% For a given height, change the width
ax = gca;
ax.Units = 'pixels';
ax.Position(3) = ax.Position(4)/slope;
You can achieve that with
axis equal
which, according to the documentation,
uses the same length for the data units along each axis.
You may want to also use
axis tight
which
fits the axes box tightly around the data by setting the axis limits equal to the range of the data
Follow up your commands with a declaration that you'll be working in pixels, and then set the width to the height:
ax.Units = 'pixels';
ax.Position(3) = ax.Position(4);
I am writing a GUI in MATLAB (guide) where user will be shown 2 images(both images are positioned side by side in single gui window) from a series of images (but each drifted little bit) and will be allowed to select area of interest.
I want user to select working are in image 1 while simultaneously highlighting the selected area in image 2, so that it is easier to judge whether the feature of interest has drifted out of selected area or not. How to do that?
I am using following answer to select and crop area of interest(just FYI):
crop image with fixed x/y ratio
Here is a way to do it using imrect and its addNewPositionCallback method. Check here for a list of available methods.
In the following figure I create 2 axes. On the left that's the original image and on the right that's the "modified" image. By pressing the pushbutton, imrect is called and the addNewPositionCallback method executes a function, called GetROIPosition that is used to get the position of the rectangle defined by imrect. At the same time, in the 2nd axes, a rectangle is drawn with the same position as that in the 1st axes. To be even more fancy you can use the setConstrainedPosition to force the rectangle to be enclosed in a given axes. I'll let you do it :)
Here is the whole code with 2 screenshots:
function SelectROIs(~)
%clc
clear
close all
%//=========================
%// Create GUI components
hfigure = figure('Position',[300 300 900 600],'Units','Pixels');
handles.axesIm1 = axes('Units','Pixels','Position',[30,100,400 400],'XTick',[],'YTIck',[]);
handles.axesIm2 = axes('Units','Pixels','Position',[460,100,400,400],'XTick',[],'YTIck',[]);
handles.TextaxesIm1 = uicontrol('Style','Text','Position',[190 480 110 20],'String','Original image','FontSize',14);
handles.TextaxesIm2 = uicontrol('Style','Text','Position',[620 480 110 20],'String','Modified image','FontSize',14);
%// Create pushbutton and its callback
handles.SelectROIColoring_pushbutton = uicontrol('Style','pushbutton','Position',[380 500 120 30],'String','Select ROI','FontSize',14,'Callback',#(s,e) SelectROIListCallback);
%// ================================
%/ Read image and create 2nd image by taking median filter
handles.Im = imread('coins.png');
[Height,Width,~] = size(handles.Im);
handles.ModifIm = medfilt2(handles.Im,[3 3]);
imshow(handles.Im,'InitialMagnification','fit','parent',handles.axesIm1);
imshow(handles.ModifIm,'InitialMagnification','fit','parent',handles.axesIm2);
guidata(hfigure,handles);
%%
%// Pushbutton's callback. Create a draggable rectangle in the 1st axes and
%a rectangle in the 2nd axes. Using the addNewPositionCallback method of
%imrect, you can get the position in real time and update that of the
%rectangle.
function SelectROIListCallback(~)
hfindROI = findobj(handles.axesIm1,'Type','imrect');
delete(hfindROI);
hROI = imrect(handles.axesIm1,[Width/4 Height/4 Width/2 Height/2]); % Arbitrary size for initial centered ROI.
axes(handles.axesIm2)
rectangle('Position',[Width/4 Height/4 Width/2 Height/2],'EdgeColor','y','LineWidth',2);
id = addNewPositionCallback(hROI,#(s,e) GetROIPosition(hROI));
end
%// Function to fetch current position of the moving rectangle.
function ROIPos = GetROIPosition(hROI)
ROIPos = round(getPosition(hROI));
axes(handles.axesIm2)
hRect = findobj('Type','rectangle');
delete(hRect)
rectangle('Position',ROIPos,'EdgeColor','y','LineWidth',2);
end
end
The figure after pressing the button:
And after moving the rectangle around:
Yay! Hope that helps! Nota that since you're using GUIDE the syntax of the callbacks will look a bit different but the idea is exactly the same.
I'm working on a gui and using GUIDE. It loads and image and has the user draw an ROI around a point (the particle ROI). I would then like to have two sliders for creating a second ROI (the Scan ROI) where the user can use sliders to set the width and height of the second roi and see it updated on the image. The sliders seem to work ok but my gui keeps drawing a new roi on top of the image so it gets messy looking really fast. I would like to remove the user sizeable roi from the image before redrawing it (while still keeping the original particle ROI on the image. I currently do it the following way :
Inside the callback for the setroi size button (this should be for the particel ROI)
handles=guidata(hObject);
particleroiSize=imrect;% - draw a rectagle around the particle to get a meausr eof ROI size
roiPoints=getPosition(particleroiSize); %-get tha parameters fo the rectanlge
partX1 = round(roiPoints(1));
partY1 = round(roiPoints(2));
partX2 = round(partX1 + roiPoints(3));
partY2 = round(partY1 + roiPoints(4)); % these are the ROi positions in pixels
roiHeight = round(roiPoints(3)); % - these are just the ROI width and height
roiWidth = round(roiPoints(4));
handles=guidata(hObject); %_ update all the handles...
handles.partX1=partX1;
handles.partX2=partX2;
handles.partY1=partY1;
handles.partY2=partY2;
handles.roicenterX = (partX1 + round(roiPoints(3))/2);
handles.roicenterY= (partY1 + round(roiPoints(4))/2);
handles.roiHeight = roiHeight;
handles.roiWidth = roiWidth;
current_slice = round(get(handles.Image_Slider,'Value'));
particleImage=handles.Image_Sequence_Data(partY1:partY2,partX1:partX2,current_slice);
handles.particleImage=particleImage;
set(handles.RoiSizeDisplay,'String',strcat('Particle ROI is ',' ',num2str(roiHeight),' ', ' by ',num2str(roiWidth)) );
guidata(hObject,handles);
And then inside the call back for the sliders that set the Scan ROI size I have (this is inside two different sliders one adjusts the width and one the height :
handles=guidata(hObject);
try
delete(handles.ScanArea);
% plus any cleanup code you want
catch
end
WidthValue = get(handles.ScanAreaSliderWidth,'value');
HeightValue = get(handles.ScanAreaSliderHeight,'value');
set(handles.ScanAreaWidthDisplay,'String',strcat('Scan Area Width is ',' ', num2str(WidthValue))); % sets the display..now to do the drawing...
%h = imrect(hparent, position);
%position = [Xmin Ymin Width Heigth];
position = [ round(handles.roicenterX-WidthValue/2) round(handles.roicenterY-HeightValue/2) WidthValue HeightValue];
handles.ScanArea = imrect(handles.Image_Sequence_Plot,position);
%h = imrect(hparent, position)
handles=guidata(hObject);
guidata(hObject, handles);
But it never deletes the scan area ROI and keeps redrawign over it..I thought the try...catch would work but it doens't seem to. Am I making extra copies of the ROI or something? Please help..
Thanks.
If you need to delete the ROI drawn with imrect, you can use findobj to look for rectangle objects (which are of type "hggroup") and delete them:
hfindROI = findobj(gca,'Type','hggroup');
delete(hfindROI)
and that should do it. Since you first draw particleroiSize, which is of the hggroup type as well, you might not want to delete all the outputs from the call to findobj. If there are multiple rectangles in your current axis, then hfindROI will contain multiple entries. As such you might want to delete all of them but the first one, which corresponds to particleroiSize.
I hope i got your question right. If not please ask for clarifications!
Thanks. This worked perfectly except that I had to use
hfindROI = findobj(handles.Image_Sequence_Plot,'Type','hggroup');
delete(hfindROI(1:end-1))
to get rid of everything but the first ROI, so I guessteh hggoup objects are added at the start ? (I thought I would use deleted(hfindROI(2:end)) to delete all but the first. Also, why does hfindROI return a list of numbers? Do they represent the hggroup objects or something like that?
thanks..
I have an inverted pendulum video here which is 33 second length. The objective is to plot a red point in the center of moving rectangle part of the pendulum and to plot a line along the black stick calculating its angle for every frame.
I have handled the video frame by frame. Then I have used Object Detection In A Cluttered Scene Using Point Feature Matching. It would be good if I had access to the matching point's indexes and then I would easily calculate the angle.
I have thought that I can get the moving rectangle part's region and seek the similar regions in the next frames. But this solution seems too local.
I do not know which techniques to apply.
clear all;
clc;
hVideoFileReader = vision.VideoFileReader;
hVideoPlayer = vision.VideoPlayer;
hVideoFileReader.Filename = 'inverted-pendulum.avi';
hVideoFileReader.VideoOutputDataType = 'single';
while ~isDone(hVideoFileReader)
grayFrame = rgb2gray(step(hVideoFileReader));
frame = step(hVideoFileReader);
if isFirstFrame
part = grayFrame(202:266,202:282); % #moving part's region
isFirstFrame = false;
subplot(1,2,1);
imshow(part);
end
partPoints = detectSURFFeatures(part);
grayFramePoints = detectSURFFeatures(grayFrame);
hold on;
subplot(1,2,1), plot(partPoints .selectStrongest(10));
subplot(1,2,2), imshow(grayFrame);
subplot(1,2,2), plot(grayFramePoints .selectStrongest(20));
frame2 = pointPendulumCenter(frame);
frame3 = plotLineAlongStick(frame2);
step(hVideoPlayer, frame3);
hold off;
end
release(hVideoFileReader);
release(hVideoPlayer);
%% #Function to find the moving part's center point and plot a red dot on it.
function f = pointPendulumCenter(frame)
end
%% #Function to plot a red line along the stick after calculating the angle of it.
function f = plotLineAlongStick(frame)
end
It would make the problem much easier if your camera did not move. If you take your video with a stationary camera (e.g. mounted on a tripod) then you can use vision.ForegroundDetector to segment out moving objects from the static background.
I need to draw vertical lines at regular intervals in a rectangular box. this is what i have used so far:
xmin=000;
xmax=70000;
ymin=0;
ymax=1000;
line1Val=900;
line2Val=600;
line3Val=300;
xlim([xmin xmax])
ylim([ymin ymax])
xl=get(gca,'XLim');
line(xl,[line1Val line1Val],'Color','y');
line(xl,[line2Val line2Val],'Color','y');
line(xl,[line3Val line3Val],'Color','y');
hold on ;
rectangle('Position',[120000,900,(280000-120000),37],'faceColor','k')
so the width of the rectangle is 160000 units i want to divide this into 4 , where the vertical line is of a different color(say red) and the height of the line is 37 units.
any ideas on how i can draw this without drawing 4 rectangles whose edges are red and are filled with black color.
You could use the parameters xstart,ystart,width and height for drawing your rectangle:
rectangle('Position',[xstart,ystart,width,height],'faceColor','k');
After that, you could determine the line positions in a loop and simply draw these lines:
for i = 1:3
x = xstart+i*width/4;
line([x x],[ystart ystart+height],'Color','r');
end
If you want a red line at the start and end of the rectangle, let i = 0:4.