Finding an image inside image

[codergautam]

I want to know whether it's possible to use this lib to find if an image buffer is inside another image buffer. For example to identify objects in a screen screenshot. I have both buffers, one of a larger image and one of a smaller image.

I'm new to OpenCV and it would be really helpful if someone can guide me in the right direction.

Thanks

[sidorares]

Yes, example below:

const haystack = cv.imdecodeAsync(screenshotImage);
const needle = cv.imdecodeAsync(templateImage)
const matched = await haystack.matchTemplateAsync(
    needle,
    cv.TM_CCOEFF_NORMED
  );
const minMax = await matched.minMaxLocAsync();
const { x, y } = minMax.maxLoc;
const accuracy = minMax.maxVal;

if you need to find all matches, just paint out matched matrix and calculate next max value with minMaxLocAsync

async function findAll({ haystack, needle, treshold, maxResults }) {
  const result = [];
  const matched = await haystack.matchTemplateAsync(
    needle,
    cv.TM_CCOEFF_NORMED
  );
  const w = needle.cols;
  const h = needle.rows;

  while (1) {
    if (maxResults > 0 && result.length >= maxResults) {
      break;
    }
    const minMax = await matched.minMaxLocAsync();
    if (minMax.maxVal < treshold) {
      break;
    }
    const { x, y } = minMax.maxLoc;
    matched.drawRectangle(
      new cv.Rect(x, y, w, h),
      new cv.Vec3(0, 0, 0),
      -1,
      cv.LINE_8
    );
    result.push({ x, y, accuracy: minMax.maxVal });
  }
  return result;
}

[codergautam]

Thanks a lot, I will try this out!