Description : You need to implement a program to detect edges in an input image using

Sobel method.

o Input : The following value from keyboard.

$$ Input image file name $($square size, and $.$ppm format $($P$6)).$

$$ threshold value for edge detection $($integer$).$

o You can use one of the Sobel filters in the lecture slide.

o Your program needs to do the following basically:

$$ Get input values above.

$$ Perform $$ReadPPM$$ for input image.

$$ Perform $$CreatPPM$$ for output image.

$$ Initialize all pixel values of output image as white $(255).$

$$ Convolute input image with the Sobel filter $($Gx$)$ you selected, and save the

results as an array, and convolute input image with the Sobel filter $($Gy$)$ you

selected, and save the results as a different array. You need to apply this step

to gray scale values of all pixels.

$$ Apply an equation $($i$.$e$,$ Detect edges $=$ sqrt $(($outputs by Gx$)2+($outputs by

Gy$)2$

$)$ to the above arrays.

$$ If the result of this formula is larger than the input threshold value, put a black

pixel into the output image created by $$CreatPPM$$ above using $$PutRPixel$,$

PutGPixel, and PutBPixel$.$

$$ Perform $$WritePPM$$ for output images.

o Output : an image file $(.$ppm format, i$.$e$.,$ edge.ppm$)$ as edge detection result, in

which edge lines are black pixels, and all others are white pixels