HW1.js

'use strict'

const cv = require('opencv')

function main () {
  cv.readImage(process.argv[2], function (err, inputMat) {
    if (err || inputMat.height() === 0 || inputMat.width === 0) {
      console.log('input image error!')
      return
    }

    let upsideDown = inputMat.copy()
    let rightLeft = inputMat.copy()
    let diagonal = inputMat.copy()
    let height = inputMat.height()
    let width = inputMat.width()

    console.log('input image =', width, ' x ', height)

    /**
     * Matrix(rows, cols)
     * Use matrix.pixel(ro, j) to get the pixel
     *     matrix.pixel(i, j, [r,g,b]) to set the pixel
     **/
    for (var i = 0; i < width; i++) {
      for (var j = 0; j < height; j++) {
        upsideDown.pixel(i, j, inputMat.pixel(height - i - 1, j))
        rightLeft.pixel(i, j, inputMat.pixel(i, height - j - 1))
        diagonal.pixel(i, j, inputMat.pixel(j, i)) // invert x and y
      }
    }

    upsideDown.save('./output/HW1/HW1_upside_down.bmp')
    rightLeft.save('./output/HW1/HW1_right_left.bmp')
    diagonal.save('./output/HW1/HW1_diagonal.bmp')
    console.log('finished!')
  })
}

main()