fabric/src/filters/shaders/invert.ts

Object model for HTML5 canvas, and SVG-to-canvas parser. Backed by jsdom and node-canvas.

export const fragmentSource = `
  precision highp float;
  uniform sampler2D uTexture;
  uniform int uInvert;
  uniform int uAlpha;
  varying vec2 vTexCoord;
  void main() {
    vec4 color = texture2D(uTexture, vTexCoord);
    if (uInvert == 1) {
      if (uAlpha == 1) {
        gl_FragColor = vec4(1.0 - color.r,1.0 -color.g,1.0 -color.b,1.0 -color.a);
      } else {
        gl_FragColor = vec4(1.0 - color.r,1.0 -color.g,1.0 -color.b,color.a);
      }
    } else {
      gl_FragColor = color;
    }
  }
`;