texture resize glsl

texture-resize.glsl

float scale(float _val, float _scale) {
    _val -= 0.5;
    _val *= _scale;
    _val += 0.5;
    return _val;
  }

  vec2 coverImage(vec2 _pos) {
    float rS = uRes.x / uRes.y;
    float rI = uImageRes.x / uImageRes.y;

    float scaleX = 1.;
    float scaleY = 1.;

    // scale UVS
    if (rS > rI) {
      scaleY = rI / rS;
    } else {
      scaleX = rS / rI;
    }

    _pos.x = scale(_pos.x, scaleX);
    _pos.y = scale(_pos.y, scaleY);

    return _pos;
  }