Detect the edge and mesaure the distance measurement of jet?

Question

Irfan Tahir 2017-7-4

0
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https://ww2.mathworks.cn/matlabcentral/answers/347354-detect-the-edge-and-mesaure-the-distance-measurement-of-jet

回答： Dimitris Iliou 2017-7-14

Hi, i have high speed images of a jet, now i need to measure its penetration. Since i am a beginner with matlab therefore needed help to measure it. There is a jet with an angle. I need to detect the jet edge and to measure it distance (horizontal) from the origin.

    % code clear all
mmPerPixel = 0.101;
Img=imread('C00018.tif');
[rows, columns, numberOfColorChannels] = size(Img);
pixelsPermm = 25 / mmPerPixel;
x1 = 15; % Starting column.
x2 = x1 + pixelsPermm;
y = round(0.9 * rows);
edge_r=edge(Img,'Roberts');
figure(1);imshow(Img, [0 2500]);
figure(2); imshow(edge_r);
line([x1, x2], [y, y], 'Color', 'r', 'LineWidth', 3);
text(x1, y-20, '25 cm', 'Color', 'r', 'FontSize', 20);

after using the code, i can see the horizontal length of the jet but i dont have its numerical value. I need to measure it till the edge. Needed help with detection. I dont know much about the edge command and its value. or may be i am using the wrong function. Help will be really appreciated.