How to work in a specific area in an image ?

After using the object detection technique (https://fr.mathworks.com/help/vision/examples/object-detection-in-a-cluttered-scene-using-point-feature-matching.html) and after i found the desired object in image and drew the rectangle. How can i start working inside the rectangle, for example to draw the contour of the object inside the green rectanle? I am new to the image processing tools and to matlab

Answer 1

[Ameer Hamza]

Use imcrop().

smallImage = imcrop(originalImage, rectangle);

[Theodor Al Saify]

The problem is i don't have a rectangle, i have a line that was drawen. if i try smallImage = imcrop(originalImage, line); i get an error.

[Ameer Hamza]

"i found the desired object in image and drew the rectangle"

How did you draw the rectangle?

[Theodor Al Saify]

using the line function

[Ameer Hamza]

Still, if you have two edges of the line, you can construct a rectangle. Can you show, what are the values you used to draw the line?

[Image Analyst]

Use the rows and columns:

smallImage = originalImage(row1:row2, column1:column2, :);

[Theodor Al Saify]

This is the code that i used to draw the rectangle it uses a list of x and y .

[Ameer Hamza]

Try the following lines

BB = [1, 1, size(boxImage,2) size(boxImage,1)];
newImage = imcrop(sceneImage, BB);
figure;
imshow(newImage);

or as @Image Analyst suggested,

newImage = sceneImage(1:size(boxImage,1), 1:size(boxImage,2), :);
figure;
imshow(newImage);

[Theodor Al Saify]

the first solution cropped a piece of the whole detected object. in the second solution i received an Index exceeds matrix dimensions error.

[Theodor Al Saify]

1 , 1 parameter is not correct it should be the bottom left of the detected object

[Ameer Hamza]

Can you attach the live script you are using for this question? It will be easy to give a proper answer if the actual image is available.

[Ameer Hamza]

@Theodor Al Saify, it is very difficult to give a correct line of code because I don't know what the variable name represent. If you can attach the file, it will be easy to give the correct answer.

[Theodor Al Saify]

clc; warning('off','Images:initSize:adjustingMag'); boxImageRGB = imread('img5.JPG'); boxImage = rgb2gray(boxImageRGB); figure; imshow(boxImage); title('Image of a Box'); sceneImageRGB = imread('img2.JPG'); sceneImage = rgb2gray(sceneImageRGB); figure; imshow(sceneImage); title('Image of a Cluttered Scene');

boxPoints = detectSURFFeatures(boxImage); scenePoints = detectSURFFeatures(sceneImage); figure; imshow(boxImage); title('100 Strongest Feature Points from Box Image'); hold on; plot(selectStrongest(boxPoints, 100)); figure; imshow(sceneImage); title('300 Strongest Feature Points from Scene Image'); hold on; plot(selectStrongest(scenePoints, 300)); [boxFeatures, boxPoints] = extractFeatures(boxImage, boxPoints); [sceneFeatures, scenePoints] = extractFeatures(sceneImage, scenePoints); boxPairs = matchFeatures(boxFeatures, sceneFeatures); matchedBoxPoints = boxPoints(boxPairs(:, 1), :); matchedScenePoints = scenePoints(boxPairs(:, 2), :); figure; showMatchedFeatures(boxImage, sceneImage, matchedBoxPoints, ... matchedScenePoints, 'montage'); title('Putatively Matched Points (Including Outliers)'); [tform, inlierBoxPoints, inlierScenePoints] = ... estimateGeometricTransform(matchedBoxPoints, matchedScenePoints, 'affine'); figure; showMatchedFeatures(boxImage, sceneImage, inlierBoxPoints, ... inlierScenePoints, 'montage'); title('Matched Points (Inliers Only)'); boxPolygon = [1, 1;... % top-left size(boxImage, 2), 1;... % top-right size(boxImage, 2), size(boxImage, 1);... % bottom-right 1, size(boxImage, 1);... % bottom-left 1, 1]; % top-left again to close the polygon newBoxPolygon = transformPointsForward(tform, boxPolygon); figure; imshow(sceneImage); hold on; line(newBoxPolygon(:, 1), newBoxPolygon(:, 2), 'Color', 'y'); title('Detected Box'); fprintf('new Box Polygon x ') disp(newBoxPolygon(:, 1)); fprintf('new Box Polygon y ') disp(newBoxPolygon(:, 2));

%crop the detected zone BB = [newBoxPolygon(1, 1), newBoxPolygon(1, 1), size(boxImage,1) size(boxImage,2) ]; newImage = imcrop(sceneImage, BB); figure; imshow(newImage);

% newImage = sceneImage(1:size(boxImage,1),1:size(boxImage,2),:); % figure; % imshow(newImage);

[Theodor Al Saify]

this is the code i am using , i changed the parameters of your code in order to find the correct coordinate .

[Ameer Hamza]

So is your problem solved?

[Theodor Al Saify]

no still i can't find the right starting point to start the rectangle

[Ameer Hamza]

It appears that you made a mistake in this line. the second element should be newBoxPolygon(1, 2).

BB = [newBoxPolygon(1, 1), newBoxPolygon(1, 2), size(boxImage,1) size(boxImage,2) ];

try it now.

[Theodor Al Saify]

Same result :( i tired all the combination possible

[Ameer Hamza]

Please also share img2.jpg and img5.jpg as I am not able to replicate the problem as described by you.

[Theodor Al Saify]

img5

[Theodor Al Saify]

Image2

[Ameer Hamza]

There!!! Now I am able to see properly what is going on. Replace BB line with following

BB = [min(newBoxPolygon(:, 1)), min(newBoxPolygon(:, 2)), size(boxImage,1) size(boxImage,2) ];

[Theodor Al Saify]

Thank you it works .

[Ameer Hamza]

You are welcome.

Answer 2

[Theodor Al Saify]

i am working on this image, i detected the desired object and drew a line around it. Now i want to crop the detected object to start working in it's area.

Answer 3

[Theodor Al Saify]

when using ur code i get this result. the starting point of the rectangle is not correct

[Ameer Hamza]

@Theodor Al Saify, please use the comment section for discussion.

[Theodor Al Saify]

Ok no problem