How can I change the resolution of kinect V2 in matlab?

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sufian ahmed 2017-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/346831-how-can-i-change-the-resolution-of-kinect-v2-in-matlab

评论： Walter Roberson 2019-7-2

Kinect V2 color stream supported format is : 1920x1080. But kinect V2 depth stream format is : 512x424. Now when I start live steam for both sensors then they have different sizes because of different resolution. I cant resize them, because I need coordinates . so when I resize using Imresize(),the coordinates are not matched. I already read matlab documentation.They said hardware only supports this two format respectively.Now How can i do this in code so that both stream have the same resolution. I tried two days long but failed.

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Answer 1

Walter Roberson 2017-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/346831-how-can-i-change-the-resolution-of-kinect-v2-in-matlab#answer_272435

According to http://smeenk.com/kinect-field-of-view-comparison/ the fields of view of the color sensor and depth sensor are different, 84.1 x 53.8 degrees compared to 70.6 x 60 degrees, so having the depth sensor return the same resolution as the color sensor (or an integer reduction thereof) would be misleading.

The solutions appear to be discussed https://www.mathworks.com/matlabcentral/answers/268152-mapping-rgb-and-depth-kinect-v2

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Walter Roberson 2017-7-2

My only PC has been sitting in my junk pile for the last decade, so I cannot experiment with the Kinect v2 that I do not have -- but I would imagine that it is not much work to change the v1 source code to support v2.

"why i need to do calibration."

I do not care whether you calibrate or not. It is your project, not mine.

Imagine you have two cameras looking in vaguely the same direction, but one of the two of them has its lens higher and off to the side of the other, and one of the two of them has a fish-eye lens, and one of the two of them is higher resolution than the other. And you want to bring them into the same resolution for what-ever reason.

Now you could bring them into the same resolution by just doing an imresize() on one of the two of them to match the size of the other. Would that be useful? Well, it would allow you to proceed with your computations, which I suppose might be useful. But any one point in one of the two images would be only "sort of near" the point with the same row and column in the other image, if "sort of near" means something like "in the same quarter of the room". Distances in images taken with fish-eye lens are non-linear, with the physical points corresponding to adjacent pixel centers getting further and further apart as you get further from the centre of the image. You might say "But the centre of the image is Okay, right?" but remember that the centre of one of the images is not the same physical point as the centre of the other image, because the lens are not pointed at the same place.

You could also bring the two cameras into the same resolution by just doing an imcrop() to match the sizes. You will find that will would be about as useful as doing an imresize(), except with the additional tension about where you crop.

Calibration is the process of figuring out which points in the image of one camera correspond to which points in the image of the other camera so that the images can be transformed to be brought into alignment, just in case you wanted to do something potentially useful like matching the color of a physical location to the depth at that same physical location.

"please explain the process step by step"

The step by step process is to get the source code for the first toolkit I linked to, and make the minor code modifications to use Kinect v2, and then follow the steps in the manual.

"walter bro"

Note: I really do not appreciate being referred to as "bro". I am almost certainly older than your mother.

Jonathan 2019-6-26

在 MATLAB Online 中打开

Hello @Walter Roberson

I am using Kin2 Toolbox for Matlab for the Kinect V2 sensor which I got from file exchange https://www.mathworks.com/matlabcentral/fileexchange/53439-kinect-2-interface-for-matlab. There is a code for mapping the color to depth that I am trying to use. I want to determine an red object's centroid and get the depth of that object at that pixel so that I get the distance from the sensor to the object. These will then be sent to a robot for a pick and place operation. Below is the code. However the code takes only one frame and keeps on repeating those centroids' coordinates after every five seconds and doesn't update. What could I be doing wrong? Other frame acquiring functions like getsnapshot, snapshot or step are giving errors saying because its uint8 or struct. Could you please help me figure that out?

addpath('Mex');
clear all
close all
redThresh = 0.25;
k2 = Kin2('color','depth');
% images sizes
d_width = 512; d_height = 424; outOfRange = 4000;
c_width = 1920; c_height = 1080;
% Color image is to big, let's scale it down
COL_SCALE = 0.5;
% Create matrices for the images
depth = zeros(d_height,d_width,'uint16');
color = zeros(c_height*COL_SCALE,c_width*COL_SCALE,3,'uint8');
% Images used to draw the markers
depthAdditions = zeros(d_height,d_width,3,'uint8');
colorAdditions = zeros(c_height*COL_SCALE, c_width*COL_SCALE,3,'uint8');
% depth stream figure
d.h = figure;
d.ax = axes('units','pixels');
d.im = imshow(depth,[0 255]);
title('Depth Source')
% color stream figure
c.h = figure;
c.im = imshow(color,[]);
title('Color Source');
nFrame = 0;
while true
    % Get frames from Kinect and save them on underlying buffer
    validData = k2.updateData;
    
    % Before processing the data, we need to make sure that a valid
    % frame was acquired.
    if validData
        % Copy data to Matlab matrices
        depth = k2.getDepth;
        color = k2.getColor;
        
        % update depth figure
        depth8u = uint8(depth*(255/outOfRange));
        depth8uc3 = repmat(depth8u,[1 1 3]);
        set(d.im,'CData',depth8uc3 + depthAdditions);
        
        % update color figure
        color = imresize(color,COL_SCALE);
        set(c.im,'CData',color + colorAdditions);
        
    end
    
    while (nFrame<300)
      
        frame=color();
        red = frame(:,:,1);
        diffFrame = imsubtract(frame(:,:,1), rgb2gray(frame));
        diffFrame = medfilt2(diffFrame, [3 3]);
        binFrame = imbinarize(diffFrame, redThresh);
        binFrame = bwareaopen(binFrame,300);
        bw = bwlabel(binFrame, 8);
        
        stats = regionprops((bw), 'BoundingBox', 'Centroid');
        centroids = cat(1, stats.Centroid);
        imshow(frame)
        %drawnow
        hold on
        
        %This is a loop to bound the red objects in a rectangular box.
        for object = 1:length(stats)
            bb = stats(object).BoundingBox;
            bc = stats(object).Centroid;
            rectangle('Position',bb,'EdgeColor','r','LineWidth',2)
            plot(bc(1),bc(2), '-m+')
            a=text(bc(1)+15,bc(2), strcat('X: ', num2str(round(bc(1))), '    Y: ', num2str(round(bc(2)))));
            set(a, 'FontName', 'Arial', 'FontWeight', 'bold', 'FontSize', 12, 'Color', 'yellow');
            X = bc(1); Y = bc(2);
           
            x = X;
            y = Y; 
            disp('Input Color Coordinates')
            disp([x y]);
            
            depthCoords = k2.mapColorPoints2Depth([x/COL_SCALE y/COL_SCALE]);
            
            disp('Output depth coordinates')
            disp(depthCoords);
            depthAdditions = insertMarker(depthAdditions,depthCoords,'Color','green');
            
        end
        hold off
        pause(5)
        
        nFrame = nFrame+1;
    end
end
k2.delete
close all

Jonathan 2019-7-2

Thank you Mr Roberson. It worked. However, I want to ask if it is possible that for every RGB frame taken, can I be able to take a depth image at the same time? I want that for every 5 seconds that the rgb camera is taking an image, the depth camera must also take the image of the same frame at the same time. Can that be possible? If so can you please show me how I can achieve that.

Thank you.

Walter Roberson 2019-7-2

在 MATLAB Online 中打开

maxFrame = 300;
vid = videoinput('kinect', 1);   %1 for color, 2 for depth
vid.FramesPerTrigger = 1;
vid.TriggerRepeat = maxFrame;
depth = videoinput('kinect', 2);   %1 for color, 2 for depth
depth.FramesPerTrigger = 1;
depth.TriggerRepeat = maxFrame;
start(vid);
start(depth)
for nFrame = 1 : maxFrame
    s = getdata(vid);
    d = getdata(depth);
    red = s(:,:,1);
    [...]
end

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