Well I faund the solution. CutyCapt do not have "tools/parameters" to make const img size(width or height for example) but if you have own html page(page what you can edit/update) you can convert it to image with const parameter/s.
You need to enclose yours html page (what inside body tag)content with container . in style tag or in css set parameters of that container for example width=1920px;
see code snipped
<!Doctype HTML>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>fixed layout</title>
<style>
/* This is a comment it is not read by any browser
This is where the css styling goes */
body{
color:#000;
background-color:#fff;
padding:0;
margin:0;
}
#container{
/*Styling for any element with the id="container" */
width:1912px; /* The width is fixed by pixels */
color:#fff;
background-color:red;
}
</style>
</head>
<body>
<div id="container">
<p id="content"> I have a fixed width so you can only see me and the body if your monitor has enough pixels. Otherwise you will just see me, the container</p>
</div>
</body>
</html>
Why 1912px not 1920px if you need width 1920 for example. Well if you convert html page where width is 1920 px into img using CutyCapt your output img width will be 1928 not 1920 ,dats why you need for 8px less width parameter. I think if you change padding parameter in #container you would not need to set parameter width 8px less from needed.