Digital Image Correlation

This Folder contains the matlab implementation of the Lucas-Kanade algorithm for digital image correlation, applied on a tensile test of a composite material speciment in order to determine its characteristics like Young's Modulus, ultimate tensile strenght and yield point.

The implementation foresees the radiometric compensation of the background intensity and allows to choose the transformation model between pure translation or affine.

HOW TO USE

Step-1

If we have a video of the tensile test, extract the frames you want to use with the following function:

function [ V ] = frame_extr(video_file_name,start_at_sec,n_frames_to_extract,fps,interval,path)

which allows us to extract a number of frame equal to the value assigned to the parameter "n_frames_to_extract" from the video named "video_file_name", characterized by a number of frames per second equal to "fps", with start of extraction at second "start_at_sec" and save directory "path" at intervals of second euqual to "interval".

For exmaple for extracting 50 frames from the video 'prov.mp4' (25 fps) in the directory 'frames2sec', starting at second 35 of the registration, one frame every 2 secs call:

>> V = frame_extr('prov.mp4',35,50,25,2,'frames2sec/')

Once we have the frames we are ready for the correlation step.

Step-2

Run the script "run_script.m" after assigning values to the following parameters in the script:

path=''; % the name of the directory where the frame are

crop_x1=270;%x1 coordinate of the rectangular area where to correlate, for using full image x1=0

crop_y1=20;%y1 coordinate of the rectangular area where to correlate, for using full image y1=0

crop_x2=500;%x2 coordinate of the rectangular area where to correlate, for using full image x2= images width

crop_y2=570;%y2 coordinate of the rectangular area where to correlate, for using full image x2= images height

offset_sec=35;%starting frame

num_frames=50;% numbers of frames

Please Note:

due to the high volume of computation it is recommended to compile the code using ">> coder" and adding all the files containing the% # codegen

after the compilation is dome use the _mex function to carry computation