Force imwrite to plot full screen

I have to plot a 10 full screen images made by alternately black and white columns. The difference between the 10 images is the width of the columns which vary from 2 mm to 0,18 mm I have 2 possible solutions: 1. Measure the screen width and then divide it by the width of the column so I can figure out the number of columns that I should draw (e.g. if the screen is 34 cm width and the column is 2 mm width then I can draw n = 340/2 = 180 columns ) This is what I’ve done till now :

filename = 'matrix.xlsx';//file excel with the matrix 0-1//
sheet = 1;
xlRange = 'A1:sf500';

A = xlsread(filename, sheet, xlRange)

imwrite(A , 'matrix.tif' , 'tif')

This is the output ( hence matrix.tif file )

N.B. If you zoom the image you can see that those are 500 B/W columns My problem is that independently from how many columns I try to draw ( 100, 500 or 1000 ) the resulting image has always the same width X ( but the number of columns does change ). I need to force the program to draw the columns and all the width of the screen from the beginning to the end otherwise the number of columns I calculated will be incorrect. 2. Make a loop that draws from the beginning till the end of the screen B/W column with width = 2 mm. But I have no idea how to do it. My laptop resolution is 1920x1080 ( FHD ) and my screen width is 34,5 cm ( it s a 15,6" screen). So my pixel size is 34,5/1920 = 0,01796 cm which is 0,1796 mm.