test('blackenLow test', function(){
  let url = 'https://people.cs.umass.edu/~joydeepb/robot.jpg';
  let img = lib220.loadImageFromURL(url);
  let blacken_img = blackenLow(img)
  for(let x=0; x<img.width; ++x){
    for(let y=0; y<img.height; ++y){
      let pixel = img.getPixel(x, y)
      let blacken_pixel = blacken_img.getPixel(x, y)
      for(let channel=0; channel<3; ++channel){
        if(pixel[channel] < 0.298){
          assert(blacken_pixel[channel] === 0)
        }
        if(pixel[channel] > 0.302){
          assert(blacken_pixel[channel] === pixel[channel])
        }
      }
    }
  }
});

test('saturate test', function(){
  let url = 'https://people.cs.umass.edu/~joydeepb/robot.jpg';
  let img = lib220.loadImageFromURL(url);
  let saturated_img = saturateHigh(img)
  for(let x=0; x<img.width; ++x){
    for(let y=0; y<img.height; ++y){
      let pixel = img.getPixel(x, y)
      let saturated_pixel = saturated_img.getPixel(x, y)
      for(let channel=0; channel<3; ++channel){
        if(pixel[channel] > 0.702){
          assert(saturated_pixel[channel] === 1)
        }
        if(pixel[channel] < 0.698){
          assert(saturated_pixel[channel] === pixel[channel])
        }
      }
    }
  }
});

test('gray test', function(){
  let url = 'https://people.cs.umass.edu/~joydeepb/robot.jpg';
  let img = lib220.loadImageFromURL(url);
  let gray_img = toGrayscale(img)

  for(let x=0; x<img.width; ++x){
    for(let y=0; y<img.height; ++y){
      let pixel = img.getPixel(x, y)
      let gray_pixel = gray_img.getPixel(x,y)

      for(let channel=0; channel<3; ++channel){
        if(pixel[channel] > 0.702 || pixel[channel] < 0.298){
          assert(pixelEq(pixel, gray_pixel))
        }
      }
    }
  }
});

test('imageMapXY function definition is correct', function() {
 let identityFunction = function(image, x, y) {
  return image.getPixel(x, y);
 };
 let inputImage = lib220.createImage(10, 10, [0, 0, 0]);
 let outputImage = imageMapXY(inputImage, identityFunction);
 // Output should be an image, so getPixel must work without errors.
 let p = outputImage.getPixel(0, 0);
 assert(p[0] === 0);
 assert(p[1] === 0);
 assert(p[2] === 0);
 assert(inputImage !== outputImage);
});

function pixelEq (p1, p2) {
  const epsilon = 0.002;
  for (let i = 0; i < 3; ++i) {
    if (Math.abs(p1[i] - p2[i]) > epsilon) {
      return false;
    }
  }
  return true;
};

test('identity function with imageMapXY', function() {
 let identityFunction = function(image, x, y ) {
  return image.getPixel(x, y);
 };
 let inputImage = lib220.createImage(10, 10, [0.2, 0.2, 0.2]);
 inputImage.setPixel(0, 0, [0.5, 0.5, 0.5]);
 inputImage.setPixel(5, 5, [0.1, 0.2, 0.3]);
 inputImage.setPixel(2, 8, [0.9, 0.7, 0.8]);
 let outputImage = imageMapXY(inputImage, identityFunction);
 assert(pixelEq(outputImage.getPixel(0, 0), [0.5, 0.5, 0.5]));
 assert(pixelEq(outputImage.getPixel(5, 5), [0.1, 0.2, 0.3]));
 assert(pixelEq(outputImage.getPixel(2, 8), [0.9, 0.7, 0.8]));
 assert(pixelEq(outputImage.getPixel(9, 9), [0.2, 0.2, 0.2]));
});