/**
 * Preset numbl filter scripts.
 *
 * Each is a function `out = filterImage(img)` where:
 *   - img : H x W x 3 array of doubles in [0, 255]  (RGB)
 *   - out : H x W x 3 (color) or H x W (grayscale) array in [0, 255]
 *
 * MATLAB syntax (this is what numbl runs). Values outside 0-255 are clamped
 * when the image is displayed.
 */

export interface Example {
  name: string;
  code: string;
}

export const EXAMPLES: Example[] = [
  {
    name: "Invert",
    code: `function out = filterImage(img)
  % Invert each channel
  out = 255 - img;
end
`,
  },
  {
    name: "Grayscale",
    code: `function out = filterImage(img)
  % Luminance-weighted grayscale, copied back to 3 channels
  g = 0.2989 * img(:,:,1) + 0.5870 * img(:,:,2) + 0.1140 * img(:,:,3);
  out = cat(3, g, g, g);
end
`,
  },
  {
    name: "Brighten",
    code: `function out = filterImage(img)
  % Scale brightness (min keeps it in range)
  out = min(255, img * 1.4);
end
`,
  },
  {
    name: "Sepia",
    code: `function out = filterImage(img)
  r = img(:,:,1); g = img(:,:,2); b = img(:,:,3);
  sr = 0.393*r + 0.769*g + 0.189*b;
  sg = 0.349*r + 0.686*g + 0.168*b;
  sb = 0.272*r + 0.534*g + 0.131*b;
  out = min(255, cat(3, sr, sg, sb));
end
`,
  },
  {
    name: "Swap R/B channels",
    code: `function out = filterImage(img)
  % Reorder the 3rd dimension: RGB -> BGR
  out = img(:, :, [3 2 1]);
end
`,
  },
  {
    name: "Posterize",
    code: `function out = filterImage(img)
  % Snap each channel to a few levels
  levels = 4;
  step = 255 / (levels - 1);
  out = round(img / step) * step;
end
`,
  },
  {
    name: "Increase contrast",
    code: `function out = filterImage(img)
  % Push values away from mid-gray (128)
  k = 1.6;
  out = min(255, max(0, (img - 128) * k + 128));
end
`,
  },
  {
    name: "Sobel edges",
    code: `function out = filterImage(img)
  % Edge magnitude on the grayscale image
  g = 0.2989*img(:,:,1) + 0.5870*img(:,:,2) + 0.1140*img(:,:,3);
  kx = [-1 0 1; -2 0 2; -1 0 1];
  ky = [-1 -2 -1; 0 0 0; 1 2 1];
  gx = conv2(g, kx, 'same');
  gy = conv2(g, ky, 'same');
  out = min(255, sqrt(gx.^2 + gy.^2));
end
`,
  },
  {
    name: "Box blur",
    code: `function out = filterImage(img)
  % 5x5 average blur, applied to each channel
  k = ones(5, 5) / 25;
  out = zeros(size(img));
  for c = 1:3
    out(:,:,c) = conv2(img(:,:,c), k, 'same');
  end
end
`,
  },
];

export const DEFAULT_SCRIPT = EXAMPLES[0].code;