WRNexusJS/docs/IMAGE-STYLES.md

Generated CAPTCHA image styles

The self-hosted and managed engines support 18 concrete renderers plus random.

Concrete styles

Style	Main effect	Suggested use
classic	Dots, crossing lines, glyph jitter	General default pool
collision	Overlapping coloured glyphs and bars	Medium or hard challenges
snow	Dense snow-like speckles	Medium challenges
corrosion	Eroded glyph patches and rust-like noise	Medium or hard challenges
spiderweb	Connected web lines and nodes	Medium challenges
cross-shadow	Multi-colour offset shadows	Medium challenges
split	Horizontally shifted image bands	Medium or hard challenges
split2	Vertically shifted image strips	Medium or hard challenges
cut	Slashed and interrupted character strokes	Medium challenges
darts	Radial lines and target rings	Medium challenges
distortion	Two-axis sinusoidal distortion	Medium or hard challenges
stitch	Dashed seams and cross stitches	Easy or medium challenges
striped	Diagonal and horizontal stripes	Easy or medium challenges
wave	Strong wave transformation	Medium or hard challenges
grid-noise	Grid lines and translucent cells	Easy or medium challenges
scribble	Random-walk line scribbles	Medium challenges
pixel	Pixel blocks and shifted regions	Medium challenges
broken-lines	Missing stroke segments and fragments	Medium or hard challenges

Random pool

<Captcha
  type="alphanumeric"
  action="signup"
  imageStyle="random"
  allowedStyles="classic,snow,spiderweb,distortion,wave"
  excludedStyles="collision"
  disturbance="50"
/>

The engine resolves one concrete style per challenge. Refreshing creates a new challenge and selects again. Challenge metadata contains imageStyle, requestedImageStyle, and imageStylePool; it never contains the answer.

Accessibility

Keep showAudio="true" or provide another non-visual path. High disturbance and hard renderers should not be the only completion option.