image-js/src/align/affineTransfrom/createAffineTransformModel.ts

Image processing and manipulation in JavaScript

import type { ModelFunction } from 'ml-ransac';

import type { Point } from '../../geometry/index.js';

/**
 * Generate a function that applies the given transformation parameters to a point.
 * The transform is an array of number in the format: [angle, x, y, scale].
 * @param transform - Transformation to apply.
 * @returns Function to transform a point.
 */
export function createAffineTransformModel(
  transform: number[],
): ModelFunction<Point> {
  if (transform.length !== 4) {
    throw new Error('Transform had wrong number of parameters');
  }
  return (point: Point) => {
    const angle = (transform[0] * Math.PI) / 180;
    const xTranslation = transform[1];
    const yTranslation = transform[2];
    const scale = transform[3];
    const column =
      scale * (Math.cos(angle) * point.column - Math.sin(angle) * point.row) +
      xTranslation;
    const row =
      scale * (Math.sin(angle) * point.column + Math.cos(angle) * point.row) +
      yTranslation;

    return { column, row };
  };
}