Fine-Tuning ASCII Output with Adjustments

Control contrast, gamma, dithering algorithm, edge detection threshold, and character aspect ratio to shape exactly how your ASCII art renders from any source.

The Adjustments section gives you direct control over how pixel luminance values are translated into characters. You can push contrast to create stark graphic results, pull gamma to open up shadows, compensate for monospace character proportions, and choose a dithering algorithm to add texture or simulate smooth gradients within the character set’s limited tonal range.

Adjustment controls reference

Name	Range	Default	Effect
Contrast	0.1–5 (slider); 0–10 (numeric)	1.2	Higher values increase separation between light and dark cells, making the output more graphic
Gamma	0.1–5 (slider); 0–10 (numeric)	1.0	Values below 1 brighten midtones; values above 1 darken them
Char aspect ratio	0.3–1.0 (slider); 0.1–2.0 (numeric)	0.55	Corrects for the height-to-width ratio of monospace characters; lower values make rows taller
Edge threshold	0–200 (slider); 0–500 (numeric)	30	Only visible when Edge-aware chars is on; higher values require a stronger edge before a directional character is used
Dither	None / Floyd-Steinberg / Atkinson / Ordered 4×4 / Ordered 8×8	None	Distributes quantization error or Bayer noise to simulate intermediate tones

Contrast

Contrast is applied as a linear stretch around the midpoint (0.5). At 1.0 the luminance is unchanged. Raising it to 2–3 creates a high-contrast woodcut look; lowering it toward 0.1 compresses everything toward gray.

Gamma

Gamma applies a power-curve correction to each cell’s luminance before contrast and character mapping. A gamma of 0.5 squares the luminance, brightening midtones and pulling detail out of shadows. A gamma of 2.0 darkens midtones, useful for source images that are overexposed.

Char aspect ratio

Monospace characters are approximately 0.55 times as wide as they are tall. If you leave this at the default, the output will appear correctly proportioned. If the result looks vertically squished, increase the value toward 1.0. If it looks stretched, lower it toward 0.3.

Edge threshold

This control is only visible when Edge-aware chars is checked. It sets the minimum Sobel magnitude required before a directional line character (─ ╲ │ ╱) is substituted. At low values, even subtle texture edges trigger directional characters. At high values, only strong hard edges do.

Invert

The Invert checkbox flips luminance values after gamma and contrast are applied (l = 1 − l). This swaps which characters appear on bright vs. dark areas. It is distinct from the inverse color mode, which inverts the final color output rather than the luminance used for character selection.

Edge-aware characters

The Edge-aware chars checkbox enables Sobel edge detection. When active, cells where an edge is detected above the edge threshold are drawn with a directional character instead of the brightness-mapped character. See the character sets page for the full list of directional characters.

Dithering

Dithering spreads quantization error across neighboring cells so that the overall impression of a region matches its average luminance even when only a limited set of characters is available.

Algorithm	Behavior
None	Direct brightness-to-character mapping; no error diffusion
Floyd-Steinberg	Error diffusion with 8 quantization steps; produces smooth gradients and natural-looking tonal transitions
Atkinson	Error diffusion with 16 steps; retains more contrast and creates a halftone-like look, originally from the early Macintosh
Ordered 4×4	4×4 Bayer matrix; adds a regular crosshatch pattern texture across the image
Ordered 8×8	8×8 Bayer matrix; finer regular texture, less visible patterning than 4×4

Try Atkinson dithering with the Newspaper preset (dense character set, inverse color mode, cream background). The combination produces a convincing halftone print look reminiscent of newspaper photography.