如何在fabric.js中运行WebGl图像过滤器

var canvas = new fabric.Canvas('canvas');

fabric.Image.fromURL('image.jpg', function(img) {
  canvas.add(img);
});

function customFilter(options) {
  var imageData = options.imageData;
  var data = imageData.data;

  // 在这里实现你的图像处理逻辑

  return imageData;
}

fabric.WebglFilterBackend.prototype.filterBackend = {
  applyTo2d: function(options) {
    var gl = options.gl;
    var program = options.program;
    var texture = options.texture;
    var pass = options.passes[0];

    gl.useProgram(program);
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.uniform1i(pass.uniformLocations.uSampler, 0);
    gl.uniform2fv(pass.uniformLocations.resolution, options.resolution);

    // 在这里调用自定义的WebGL图像过滤器函数
    customFilter(pass);

    gl.bindTexture(gl.TEXTURE_2D, null);
    gl.useProgram(null);
  }
};

var filter = new fabric.Image.filters.WebglFilter({
  vertexSource: 'vertexShader',
  fragmentSource: 'fragmentShader',
  filterBackend: fabric.WebglFilterBackend
});

canvas.item(0).filters.push(filter);
canvas.item(0).applyFilters();
canvas.renderAll();