love.graphics.getPixelWidth
Gets the width in pixels of the window.

The graphics coordinate system and DPI scale factor, rather than raw pixels. Use getWidth for calculations related to drawing to the screen and using the coordinate system (calculating the center of the screen, for example), and getPixelWidth only when dealing specifically with underlying pixels (pixel-related calculations in a pixel Shader, for example).
pixelwidth = love.graphics.getPixelWidth()
pixelwidth number The width of the window in pixels.