text: /**
   * Brightness and contrast adjustment
   * https://github.com/evanw/glfx.js
   * brightness: -1 to 1 (-1 is solid black, 0 is no change, and 1 is solid white)
   * contrast: -1 to 1 (-1 is solid gray, 0 is no change, and 1 is maximum contrast)
   */
  
  const BrightnessContrastShader = {
  
  	uniforms: {
  
  		'tDiffuse': { value: null },
  		'brightness': { value: 0 },
  		'contrast': { value: 0 }
  
  	},
  
  	vertexShader:
  
  		`varying vec2 vUv;
  
  		void main() {
  
  			vUv = uv;
  
  			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
  
  		}`,
  
  	fragmentShader:
  
  		`uniform sampler2D tDiffuse;
  		uniform float brightness;
  		uniform float contrast;
  
  		varying vec2 vUv;
  
  		void main() {
  
  			gl_FragColor = texture2D( tDiffuse, vUv );
  
  			gl_FragColor.rgb += brightness;
  
  			if (contrast > 0.0) {
  				gl_FragColor.rgb = (gl_FragColor.rgb - 0.5) / (1.0 - contrast) + 0.5;
  			} else {
  				gl_FragColor.rgb = (gl_FragColor.rgb - 0.5) * (1.0 + contrast) + 0.5;
  			}
  
  		}`
  
  };
  
  export { BrightnessContrastShader };
  