Function roundCorners

src/utils/ansiToPng.ts:246–265

* Zero out the alpha channel in the four corner regions outside a * quarter-circle of radius `r`. Produces rounded-rect corners.

(
  px: Uint8Array,
  width: number,
  height: number,
  r: number,
)

 * quarter-circle of radius `r`. Produces rounded-rect corners.
 */
function roundCorners(
  px: Uint8Array,
  width: number,
  height: number,
  r: number,
): void {
  const r2 = r * r
  for (let dy = 0; dy < r; dy++) {
    for (let dx = 0; dx < r; dx++) {
      const ox = r - dx - 0.5
      const oy = r - dy - 0.5
      if (ox * ox + oy * oy <= r2) continue
      // Top-left, top-right, bottom-left, bottom-right.
      px[(dy * width + dx) * 4 + 3] = 0
      px[(dy * width + (width - 1 - dx)) * 4 + 3] = 0
      px[((height - 1 - dy) * width + dx) * 4 + 3] = 0
      px[((height - 1 - dy) * width + (width - 1 - dx)) * 4 + 3] = 0
    }
  }
}

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