OneTaskBy Tim King · Updated
Halftone Generator
Image to Halftone Dots in Black, White or CMYK, Circle, Square or Line Dots
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How the Halftone Generator works
This halftone generator turns a photo into a dot screen. A halftone breaks a continuous-tone photo into a grid of dots whose size follows the brightness of the image, the trick that let newspapers and comic books print photographs with a single ink. Drop in an image and this tool screens it at the dot spacing, shape, angle and ink you choose, from a classic 45-degree black screen to a four-colour CMYK rosette. Everything runs locally.
Halftone generator: how the screen works
The image is sampled on a rotated grid. For every grid point the tool averages the pixels in the surrounding cell, converts that to a coverage value, and draws a dot whose area matches it: a dark area gets a dot almost as wide as the cell, a light area gets a pinprick, and pure white gets nothing. Area, not radius, tracks the tone, so the dot radius grows with the square root of the darkness. Seen from a distance the dots merge back into the original tones, which is exactly how printed halftones fool the eye.
Dot spacing
The spacing is the distance between dot centres in pixels of the output image. Four pixels gives a fine screen that looks almost like a photo again; forty gives huge dots that turn a portrait into pop-art abstraction. For a poster or a comic-style effect, ten to twenty is the usual sweet spot on an image around 1500 px wide. The output stays at the image's own size, up to 2000 px on the longest side, so the dot count follows the spacing directly and the Screen stat tells you roughly how many dots were placed.
Shapes and angles
Circle is the classic offset-printing dot. Square and Diamond produce a more graphic, screen-print look, and Line turns the screen into engraved-style hatching whose stroke widens where the image is darker. The single-ink screen sits at 45 degrees, the standard angle for black, because the eye is least sensitive to a diagonal pattern. The extra angle control rotates every screen by the same amount so you can try vertical, horizontal or unusual angles.
CMYK mode
Colour mode separates the image into cyan, magenta, yellow and black and screens each at its own angle: 15, 75, 0 and 45 degrees, the traditional set. The four screens are laid over one another with multiply blending so the inks combine the way overprinted inks would, and the angle offsets between them produce the characteristic rosette pattern you see under a loupe on a printed page. It is the effect that comic-book flat colour and vintage advertising reproductions are built on.
White on black
The inverse screen draws light dots on a black ground, so bright areas of the photo become the biggest dots. It suits high-contrast portraits and works well as a texture for dark backgrounds and merchandise prints where the design is knocked out of a dark garment.
FAQ
Why does the result look like a moiré pattern?
Moiré appears when the dot grid interferes with a regular pattern already in the image, such as fabric weave, brickwork or a previous halftone. Change the angle by a few degrees or make the dot spacing larger and the interference usually disappears. Very small spacings on a busy photo are the most likely to show it.
Is the output a real print-ready separation?
No. It is a visual effect rendered as one flat RGB image, not four separate plates. The CMYK option mimics the look of overprinted screens for design work, posters and social images. A printer producing genuine separations will screen the artwork with its own RIP.
What image size should I use?
Anything up to about 2000 px on the longest side is used at full size; larger images are scaled down to that limit before screening, and a note under the preview says so when that happens. For a print you will enlarge, upscale the photo first so the dots have room to be crisp.
See also: all Images tools, Audio, Video & Screen, PDF, SVG, Simulations & Screensavers, Generative Art, Chart Makers, 3D Model Viewers, Drawing Pads, Mockups & 3D Making, Diagram Makers, 3D Science, Tracker Music.
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