Function blitGlyph

src/utils/ansiToPng.ts:213–240

* Blit one glyph into the RGBA buffer at (x,y), scaled by `scale` * (nearest-neighbor). Alpha-composites over the existing background. Bold is * synthesized by boosting alpha toward opaque — a cheap approximation that * reads as heavier weight without needing a second font.

(
  px: Uint8Array,
  width: number,
  x: number,
  y: number,
  glyph: Uint8Array,
  color: AnsiColor,
  bold: boolean,
  scale: number,
)

 * reads as heavier weight without needing a second font.
 */
function blitGlyph(
  px: Uint8Array,
  width: number,
  x: number,
  y: number,
  glyph: Uint8Array,
  color: AnsiColor,
  bold: boolean,
  scale: number,
): void {
  for (let gy = 0; gy < GLYPH_H; gy++) {
    for (let gx = 0; gx < GLYPH_W; gx++) {
      let a = glyph[gy * GLYPH_W + gx]!
      if (a === 0) continue
      if (bold) a = Math.min(255, a * 1.4)
      const inv = 255 - a
      for (let sy = 0; sy < scale; sy++) {
        const rowBase = ((y + gy * scale + sy) * width + x + gx * scale) * 4
        for (let sx = 0; sx < scale; sx++) {
          const i = rowBase + sx * 4
          px[i] = (color.r * a + px[i]! * inv) >> 8
          px[i + 1] = (color.g * a + px[i + 1]! * inv) >> 8
          px[i + 2] = (color.b * a + px[i + 2]! * inv) >> 8
        }
      }
    }
  }
}

/**
 * Zero out the alpha channel in the four corner regions outside a