A Halftone , or halftone image, is an image that is made up of discrete dots rather than continuous tones.
At the same time when they are seen from a distance, then these dots blur together, together they create an illusion of continuous lines and shapes.
While halftoning an image (from a bitmap to a halftone when converted), it can be printed in very small ink.
This is why many newspapers and magazines use halftoning to print pages more efficiently.
Basically, halftoning was done mechanically by printers, which used to print images into a grid of holes through a screen. At the same time, in this printing process, ink is passed through the holes on the screen, from which dots are created in the paper.
For monochrome images in it, only one pass is required to create an image. While preparing a multicolor images, several passes or “screens” are required.
Nowadays printers are more advanced and typically do not even have physical screens. Rather, these halftone images are generated by a computer and the resulting image is printed in the paper.
By using a process called dithering, modern printers can easily randomize dot patterns, so that a more natural appearance can be created. It produces realistic images in which fully saturated ones are prepared using very little ink.
Like a standard bitmap, the quality of a halftone image depends on its resolution. A halftone that has a higher resolution (which is measured in LPI) has a greater detail, even at a lower resolution than a halftone.
By the way, the goal is to create a realistic image of this halftoning, so in some time low resolutions are used to bring an artistic effect.