Halftone lines shader

[uuuulala]

Note

Medium Risk
Adds a new public shader API and a non-trivial GLSL fragment shader with image sampling and many uniforms. Risk is mainly visual correctness and GPU performance, not security.

Overview
Adds Halftone Lines, an image filter that redraws a photo as a luminance-driven line grid.

The shader supports seven grid types (lines, linesIrregular, waves, wavesIrregular, zigzag, truchet, radial), stroke width/contrast/softness, optional original-image colors vs a two-color palette, grid contouring/noise, and grain mixer/overlay. It is exported from @paper-design/shaders and @paper-design/shaders-react as HalftoneLines with six presets.

Docs get a /halftone-lines playground (Leva controls, sample-image cycling, upload) plus registry and shader-def entries.

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[cursor]

Presets use contain not cover

Medium Severity

All halftoneLinesPresets spread defaultObjectSizing without overriding fit, so they keep contain. Sibling image filters (halftone-dots, halftone-cmyk, fluted-glass) set fit: 'cover', so the default and preset demos letterbox the source image instead of filling the canvas like the other filters.

Additional Locations (2)

• packages/shaders-react/src/shaders/halftone-lines.tsx#L48-L78
• packages/shaders-react/src/shaders/halftone-lines.tsx#L79-L109

 

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

There are 5 total unresolved issues (including 3 from previous reviews).

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[cursor]

Contouring smoothstep args inverted

High Severity

smoothstep(length(uv), 0., 1.) passes edge0 >= edge1 for nearly every fragment, which is undefined in GLSL ES 3.00. That value feeds contouring.y and thus grid rotation whenever gridContouring is non-zero, so contouring rotation becomes driver-dependent instead of a defined falloff.

 

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[cursor]

Stroke invert flips palette colors

Medium Severity

toLum always applies u_strokeInverted, and inkMix uses toLum to blend colorMid and colorFront. Enabling strokeInverted therefore swaps the palette assignment, even though docs say inversion only affects stroke width and leaves colors unchanged.

Additional Locations (1)

• packages/shaders/src/shaders/halftone-lines.ts#L296-L314

 

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