c2a static method

void c2a(Uint8List pixels, int index, int redToHide, int greenToHide, int blueToHide,)

Implementation

static void c2a(Uint8List pixels, int index, int redToHide, int greenToHide,
    int blueToHide) {
  int red = pixels[index];
  int green = pixels[index + 1];
  int blue = pixels[index + 2];
  double alpha = pixels[index + 3].toDouble();

  double a4 = alpha;

  double a1 = 0.0;
  if (red > redToHide) {
    a1 = (red - redToHide) / (255.0 - redToHide);
  } else if (red < redToHide) {
    a1 = (redToHide - red) / (redToHide);
  }
  double a2 = 0.0;
  if (green > greenToHide) {
    a2 = (green - greenToHide) / (255.0 - greenToHide);
  } else if (green < greenToHide) {
    a2 = (greenToHide - green) / (greenToHide);
  }
  double a3 = 0.0;
  if (blue > blueToHide) {
    a3 = (blue - blueToHide) / (255.0 - blueToHide);
  } else if (blue < blueToHide) {
    a3 = (blueToHide - blue) / (blueToHide);
  }

  if (a1 > a2) {
    if (a1 > a3) {
      alpha = a1;
    } else {
      alpha = a3;
    }
  } else {
    if (a2 > a3) {
      alpha = a2;
    } else {
      alpha = a3;
    }
  }

  alpha *= 255.0;

  if (alpha >= 1.0) {
    red = (255.0 * (red - redToHide) / alpha + redToHide).toInt();
    green = (255.0 * (green - greenToHide) / alpha + greenToHide).toInt();
    blue = (255.0 * (blue - blueToHide) / alpha + blueToHide).toInt();

    alpha *= a4 / 255.0;
  }
  pixels[index] = red;
  pixels[index + 1] = green;
  pixels[index + 2] = blue;
  pixels[index + 3] = alpha.toInt();
}