docs: function ConvolutionFilter(matrix, width, height)
  {
      core.AbstractFilter.call(this,
          // vertex shader
          null,
          // fragment shader
          fs.readFileSync(__dirname + '/convolution.frag', 'utf8'),
          // custom uniforms
          {
              matrix:     { type: '1fv', value: new Float32Array(matrix) },
              texelSize:  { type: '2v', value: { x: 1 / width, y: 1 / height } }
          }
      );
  }