Notes

const cv = require('opencv4nodejs');
const fs = require('fs');

// Function to decode base64 string to buffer
function base64ToBuffer(base64String) {
const base64Data = base64String.replace(/^data:image/w+;base64,/, '');
return Buffer.from(base64Data, 'base64');
}

// Base64 encoded image string
const base64Image = 'YOUR_BASE64_IMAGE_HERE';

// Decode base64 string to buffer
const buffer = base64ToBuffer(base64Image);

// Read the image buffer
const image = cv.imdecode(buffer);

// Convert the image to grayscale
const gray = image.cvtColor(cv.COLOR_BGR2GRAY);

// Apply thresholding to segment the gray areas
const binary = gray.threshold(240, 255, cv.THRESH_BINARY_INV);

// Find contours of the colorful inner image
const contours = binary.findContours(cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE);

// Get the bounding box of the largest contour (assuming inner colorful image is the largest contour)
let maxArea = -1;
let maxContourIdx = -1;
for (let i = 0; i < contours.size(); ++i) {
const contourArea = contours.get(i).area;
if (contourArea > maxArea) {
maxArea = contourArea;
maxContourIdx = i;
}
}
const boundingRect = contours.get(maxContourIdx).boundingRect();

// Get coordinates of the bounding box
const innerImageCoordinates = {
x: boundingRect.x,
y: boundingRect.y,
width: boundingRect.width,
height: boundingRect.height
};

console.log('Inner Image Coordinates:', innerImageCoordinates);

// Create a mask to fill the gray background with white
const mask = new cv.Mat();
binary.copyTo(mask);

// Draw the bounding rectangle of the inner image on the mask
cv.rectangle(mask, new cv.Point(innerImageCoordinates.x, innerImageCoordinates.y), new cv.Point(innerImageCoordinates.x + innerImageCoordinates.width, innerImageCoordinates.y + innerImageCoordinates.height), new cv.Vec(255), -1);

// Inpaint the gray areas using the mask
const result = new cv.Mat();
image.copyTo(result, mask);

// Save the result image
const resultImagePath = 'result_image.jpg';
cv.imwrite(resultImagePath, result);

console.log('Result image saved:', resultImagePath);