A Structural Engineering Professor needs to evalute the structural integrity of a damaged concrete shear wall. Several diagonal cracks formed in the wall surface as a result of seismic forces. The cracks are annotated with sharpies and a picture is taken. The professor is interested in the red cracks and wants an image which just shows the red cracks. Create a filter with a threshold value to show only the red cracks.

Write a script which imports the image $($cracked$\_$wall.jpg$)$ and filter the image:

recall that a RGB color image is saved in Matlab as a $($n x m x $3)$ matrix, where the red, green and blue channels are saved as $($n x m x$1),($n x m x$2),($n x m x$3),$ respectively. im$\_$gray is the grayscale version of the image and it is saved as a $($n x m$)$ matrix. Plot the grayscale image im$\_$gray

calculate the im$\_$ratio as the ratio of the red channel over the mean of the three channels, i$.$e$.,($double$($im$($n$,$m$,1))+$ double$($im$($n$,$m$,2))+$ double$($im$($n$,$m$,3)))/3.$ Plot the newly calculated image im$\_$ratio. $($Convert the data type to double!$)$

Hint: the resulting image should have a single channel $($ it will be a grayscale image$).$ You may also have to convert your uint$8()$ matrix into the datatype double$()$ before doing this.

create a mask im$\_$out to filter out parts of the image which are not red. The mask is a zero matrix $(0$ is black$)$ with the only non$-$zero elements in correspondence of the red cracks. These elements are such that im$\_$ratio $>$ threshold $=1\mathrm{.}9.$ Create im$\_$out that only show pixels with im$\_$ratio $>1\mathrm{.}9$ so that only the red cracks appear.