get-aspect-ratio-params.js

// Function that gets the area of the original image to crop 
// depending on the aspect ratio to transform it  toratioWidth:H
const getAspectRatioParams = (sourceWidth, sourceHeight, destinationWidth, destinationHeight) => {
  
  let width = sourceWidth;
  let height = sourceHeight;
  let x = 0;
  let y = 0;

  const imageRatio = sourceWidth / sourceHeight;
  const cropRatio = destinationWidth / destinationHeight;

  if (imageRatio > cropRatio) {
    width = (sourceHeight * destinationWidth) / destinationHeight;
    x = (sourceWidth - width) / 2;
  }

  if (imageRatio < cropRatio) {
    height = (sourceWidth * destinationHeight) / destinationWidth;
    y = (sourceHeight - height) / 2;
  }

  return {
    x,
    y,
    width,
    height,
  };
};