MATLAB: Drawing bounding box onto an image without imshow and hold on …

rectangleregionprops

Hi there. I was wondering if its possible to draw a rectangle, whose coordinates is obtained from regoingprops. I however, am not interested to show the image first. What I intend to do is to get the bounding box coordinates form regionprops, and then just superimpose it onto an image without displaying it. I would then like to save the image (saving is ok… just drawing the rectangle got me a bit tangled up 😛 ). Would appreciate any advice!

The code I'm currently using is as shown above. (It's in a for loop) where 'l' is the counter.

THANKS in advance!!!

f = figure,imshow(frame, 'Border', 'tight');
hold on; 
rectangle('Position',s(l).BoundingBox,'EdgeColor','y','LineWidth',2)
print(f, '-r80', '-djpeg', [dirName 'results' '\' jpegFiles(i).name]);
close all;

Best Answer

If you have the Computer Vision Toolbox then you can use shapeInserter

If you do not have that, then you can just assign values to the appropriate rows and columns in the array. Watch out for the possibility that the values for the coordinates are not integral

bb = s(l).BoundingBox;
from_row = ceil(bb(2));
to_row = from_row + bb(4) - 1;
from_col = ceil(bb(1));
to_col = from_col + bb(3) - 1;
yellow = [255, 255, 0];
%left and right side
frame(from_row:to_row, [from_col, to_col], 1) = yellow(1);
frame(from_row:to_row, [from_col, to_col], 2) = yellow(2);
frame(from_row:to_row, [from_col, to_col], 3) = yellow(3);
%top and bottom
frame([from_row, to_row], from_col+1:to_col-1, 1) = yellow(1);
frame([from_row, to_row], from_col+1:to_col-1, 1) = yellow(2);
frame([from_row, to_row], from_col+1:to_col-1, 1) = yellow(3);

Related Solutions

MATLAB: How can we replacing the pixel values of RGB image under bounding box with some random pixel values

Hi Sami:

It sounds like you want to set the RGB pixel value for the values in the bounding boxes. You can extract the rows and columns from the 'bboxes' variable, and then set those on the image matrix (or take a copy of the matrix to avoid altering the original). Below I show an example where I make all of the pixels in the first bounding box red. I then show the altered image using the imshow function.

% Each row of bboxes has a X, Y, width, height
cols=bboxes(1,1):sum(bboxes(1,[1 3]));
rows=bboxes(1,2):sum(bboxes(1,[2 4]));
% Make bbox 1 red:
I(rows,cols,1)=255;
I(rows,cols,2)=0;
I(rows,cols,3)=0;
figure, imshow(I);

MATLAB: Local histogram equalization manually

I'm assuming this isn't your homework since you didn't label it as homework, so this will work, however you can do it much faster with adapthisteq() or by using intlut() to make up a look up table rather than using a double for loop.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
grayImage = rgb2gray(imread('peppers.png'));
subplot(1,2,1);
imshow(grayImage);
axis on;
drawnow;
if (isa(grayImage,'uint8'))
  grayImage=double(grayImage)/255;
end
if (size(grayImage,3)==3)
  grayImage=(grayImage(:,:,1)+grayImage(:,:,2)+grayImage(:,:,3))/3; % average the RGB channels
end
windowsize = 17;
% Create an empty array
Ieq = zeros(size(grayImage,1),size(grayImage,2));
% Apply this over a NxN region around each pixel (N is odd)
n = floor(windowsize/2); % <-- N is the half size of the region ie. [-N:N,-N:N]
for r=1+n:size(grayImage,1)-n
  fprintf('Processing row #%d\n', r);
  for c=1+n:size(grayImage,2)-n
    % -- INSERT YOUR CODE BELOW ------------------------------------------
    % NOTE: For pixels near the boundary, ensure the NxN neighbourhood is still
    % inside the image (this means for pixels near the boundary the pixel may
    % not be at the centre of the NxN neighbourhood).
    
    if r-n <=1
      fromrow=1;
      torow=r+n;
    else
      fromrow=abs(r-n);
      if n+r >= size(grayImage,1)
        torow=size(grayImage,1);
      else
        torow=r+n;
      end
      
    end
    
    if c-n <= 1
      fromcol=1;
      tocol=c+n;
    else
      fromcol=abs(c-n);
      if c+n > size(grayImage,2);
        tocol=size(grayImage,2);
      else
        tocol=c+n;
      end
    end
    neighbors = grayImage(fromrow:torow, fromcol:tocol);
    counts = imhist(neighbors, 256);
    cdf = cumsum(counts);
    cdf = cdf ./ cdf(end); % Normalize.
    % Get the original value of the central pixel that we need to replace.
    centerGrayLevel = grayImage(r, c);
    % Now see what it gets mapped to.
    index = ceil(256 * centerGrayLevel);
    newPixelValue = cdf(index);
    % Do the assignment
    Ieq(r,c) = newPixelValue;
    
    % -- INSERT YOUR CODE ABOVE ------------------------------------------
    
  end
end
subplot(1,2,2);
imshow(Ieq, []);
axis on;
msgbox('Done');

Best Answer

Related Solutions

MATLAB: How can we replacing the pixel values of RGB image under bounding box with some random pixel values

MATLAB: Local histogram equalization manually

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