Function imageDataToRgb565

app.js:2693–2708

(data, w, h, bgHex)

}

function imageDataToRgb565(data, w, h, bgHex) {
  const rgb565 = new Array(w * h);
  const bg = hexToRgb(bgHex || "#000000") || { r: 0, g: 0, b: 0 };
  for (let i = 0, p = 0; i < data.length; i += 4, p++) {
    const a = data[i + 3];
    // No alpha on TFT pushImage; blend with current background for preview + export
    const r = a < 16 ? bg.r : data[i];
    const g = a < 16 ? bg.g : data[i + 1];
    const b = a < 16 ? bg.b : data[i + 2];
    const r5 = (r >> 3) & 0x1f;
    const g6 = (g >> 2) & 0x3f;
    const b5 = (b >> 3) & 0x1f;
    rgb565[p] = (r5 << 11) | (g6 << 5) | b5;
  }
  return rgb565;
}

function buildMonoBitmapFromImageData(imageData, w, h, alphaThreshold = 16, lumaThreshold = 0.35) {
  // U8g2 drawXBMP expects XBM bit order: LSB first within each byte, row-major.