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feat(editor): add --gen-texture-bayer ordered-dither pattern

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81st procedural texture: classic 4x4 Bayer ordered-dither
matrix tiled across the image. Each pixel's color comes
from interpolating bg → fg by the matrix value at
(x mod 4, y mod 4) normalized to [0, 1]:

       0  8  2 10
      12  4 14  6
       3 11  1  9
      15  7 13  5

cellSize parameter scales the matrix block (default 4 px,
giving a 16-px seamless tile; cellSize=8 gives a 32-px
chunky retro look).

Useful for 8-bit / monochrome-CRT-style backdrops, ordered-
shadow approximations on low-bit palettes, retro arcade
splash overlays, paper-spritesheet rendering, and as a
deterministic alternative to --gen-texture-noise for
binary or near-binary palettes.
This commit is contained in:
Kelsi 2026-05-09 14:20:02 -07:00
parent 6c2f5cf9ca
commit 25ada9bbfb
3 changed files with 58 additions and 0 deletions
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55
tools/editor/cli_gen_texture.cpp
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@ -3500,6 +3500,60 @@ int handleKnit(int& i, int argc, char** argv) {
return 0;
}
int handleBayer(int& i, int argc, char** argv) {
// Classic 4x4 ordered-dither Bayer matrix tiled across the
// image. Each pixel's color comes from interpolating bg → fg
// by the matrix value at (x mod 4, y mod 4) normalized to
// [0, 1]. Distinctive retro / dithered look — useful for
// 8-bit-style backdrops, monochrome-CRT effects, ordered-
// shadow approximations on low-bit palettes.
std::string outPath = argv[++i];
std::string aHex = argv[++i]; // dark color (matrix value 0)
std::string bHex = argv[++i]; // light color (matrix value 15)
int cellSize = 4; // pixels per matrix cell
int W = 256, H = 256;
parseOptInt(i, argc, argv, cellSize);
parseOptInt(i, argc, argv, W);
parseOptInt(i, argc, argv, H);
if (W < 1 || H < 1 || W > 8192 || H > 8192 ||
cellSize < 1 || cellSize > 256) {
std::fprintf(stderr,
"gen-texture-bayer: invalid dims (W/H 1..8192, "
"cellSize 1..256)\n");
return 1;
}
uint8_t ar, ag, ab, br_, bg_, bb_;
if (!parseHexOrError(aHex, ar, ag, ab, "gen-texture-bayer")) return 1;
if (!parseHexOrError(bHex, br_, bg_, bb_,
"gen-texture-bayer")) return 1;
// 4x4 Bayer matrix values 0..15 (ordered-dither standard).
static const int kBayer4[4][4] = {
{ 0, 8, 2, 10},
{12, 4, 14, 6},
{ 3, 11, 1, 9},
{15, 7, 13, 5},
};
std::vector<uint8_t> pixels(static_cast<size_t>(W) * H * 3, 0);
for (int y = 0; y < H; ++y) {
int my = (y / cellSize) & 3;
for (int x = 0; x < W; ++x) {
int mx = (x / cellSize) & 3;
// Normalize 0..15 to 0..1 and interpolate.
float t = kBayer4[my][mx] / 15.0f;
uint8_t r = static_cast<uint8_t>(ar + t * (br_ - ar));
uint8_t g = static_cast<uint8_t>(ag + t * (bg_ - ag));
uint8_t b = static_cast<uint8_t>(ab + t * (bb_ - ab));
setPixelRGB(pixels, W, x, y, r, g, b);
}
}
if (!savePngOrError(outPath, W, H, pixels, "gen-texture-bayer")) return 1;
printPngWrote(outPath, W, H);
std::printf(" a / b : %s / %s\n", aHex.c_str(), bHex.c_str());
std::printf(" cell : %d px (4x4 matrix → %d-px tile)\n",
cellSize, cellSize * 4);
return 0;
}
int handleHalftone(int& i, int argc, char** argv) {
// Halftone: regular grid of dots whose radii grow with a
// configurable gradient direction (vertical, horizontal, or
@ -5916,6 +5970,7 @@ constexpr TextureEntry kTextureTable[] = {
{"--gen-texture-crackle", 3, handleCrackle},
{"--gen-texture-star", 3, handleStar},
{"--gen-texture-halftone", 3, handleHalftone},
{"--gen-texture-bayer", 3, handleBayer},
};
} // namespace