export const fragmentSource = `
  precision highp float;
  uniform sampler2D uTexture;
  uniform float uContrast;
  varying vec2 vTexCoord;
  void main() {
    vec4 color = texture2D(uTexture, vTexCoord);
    float contrastF = 1.015 * (uContrast + 1.0) / (1.0 * (1.015 - uContrast));
    color.rgb = contrastF * (color.rgb - 0.5) + 0.5;
    gl_FragColor = color;
  }`;