tensorflow-crop-create-images.js

// i'm using opencv4nodejs to load a file into a tensorflow tensor
const cv = require('opencv4nodejs');
const mat = cv.imread('./tmp/lenna.png')
const size = {w: mat.cols, h: mat.rows}


const mat3 = new cv.Mat(rect.h, rect.w, cv.CV_8UC3);
mat.getRegion(new cv.Rect(rect.x, rect.y, rect.w, rect.h)).copyTo(mat3)

cv.imwrite('./tmp/cv.png', mat3)


const tf = require('@tensorflow/tfjs-node');

// I want to crop this rect
const rect = {
	x: 171,
	y: 422,
	w: 9,
	h: 8
}

// this is the address in the image of the pixel value followed through the tensors calculation
const address = [
	0,
	422+1,
	171+4,
	0
]

// Some function to be able to see what is happening inside tensors 
const fact = function (array) {
	if (array.length === 0) {
		return 1;
	}
	return array[0] * fact(array.slice(1));
};

const addressToIndex = function (address, shape) {
	return address.map((a, index) => a * fact(shape.slice(index + 1))).reduce((a, b) => a + b);
};

const logAddress = function(tensor, address){
	console.log(address, getPixelValue(address, tensor.dataSync()[addressToIndex(address, shape)]))
}

const intTensor = tf.tensor4d(mat.getData(), [1, size.h, size.w, 3])
const floatTensor = intTensor.div(255);

// if i'm logging 
logAddress(address, floatTensor)

const cropped = tf.image.cropAndResize(floatTensor, [[rect.y/size.h, rect.x/size.w, (rect.y+rect.h)/size.h, (rect.x+rect.w)/size.w]], [0], [rect.h, rect.w], 'nearest');

logAddress(address, floatTensor)

const croppedValues = cropped.mul(255).toInt().dataSync();
const d = new Uint8Array(croppedValues);
const mat2 = new cv.Mat(d, rect.h, rect.w, cv.CV_8UC3);
const mat3 = new cv.Mat(rect.h, rect.w, cv.CV_8UC3);
mat.getRegion(new cv.Rect(rect.x, rect.y, rect.w, rect.h)).copyTo(mat3)


cv.imwrite('./tmp/cv.png', mat3)
cv.imwrite('./tmp/tf.png', mat2)