precision highp float;

varying vec2 v_TexCoords;
uniform sampler2D u_Texture;

float luma(vec3 v) 
{
  return dot(v, vec3(0.2989, 0.5870, 0.1140));
}

void main()
{
  vec2 uv = vec2(v_TexCoords.x, 1.0 - v_TexCoords.y);
  vec4 base;
  base.xyz = texture2D(u_Texture, uv).xyz;
  base.w = luma(base.xyz);
  gl_FragColor = base;
}