how to do pixel analysis on the screen? - c++

Question

I need to save to an array (regular or two-dimensional) the color of each pixel from a certain area. The area should change for example: from 100(x) and 100(y) to 200, 200. Another example: from 0, 0 to 1920, 1080. Then use if and for, where you can specify the desired color and search area. The area may coincide with the area placed in the array, or it may be smaller than in the array. If a color was found, for example 255 (red). Then you need to write down its coordinates, for example in x and y. Please leave comments in the code. I'm new to C++. I use Visual Studio. I need the function to be executed very often. About 30 ms. I understand that as the speed increases, the load increases. Is there any way to reduce the load on the CPU? I use windows.
This is not my code. It doesn't work for me. I don't have enough knowledge to write code that reads from the screen.
#include <Windows.h>
#include <iostream>
using namespace std;
int main() {
int width = GetSystemMetrics(SM_CXSCREEN);
int height = GetSystemMetrics(SM_CYSCREEN);
HDC hdcScreen = GetDC(NULL);
HDC hdcCompatible = CreateCompatibleDC(hdcScreen);
HBITMAP hBitmap = CreateCompatibleBitmap(hdcScreen, width, height);
HGDIOBJ hOld = SelectObject(hdcCompatible, hBitmap);
BitBlt(hdcCompatible, 0, 0, width, height, hdcScreen, 0, 0, SRCCOPY);
BITMAPINFO bmi;
ZeroMemory(&bmi, sizeof(BITMAPINFO));
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = width;
bmi.bmiHeader.biHeight = height;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
int** pixels = new int*[height];
for (int i = 0; i < height; i++) {
pixels[i] = new int[width];
}
GetDIBits(hdcScreen, hBitmap, 0, height, (LPVOID*)pixels, &bmi, DIB_RGB_COLORS);
SelectObject(hdcCompatible, hOld);
DeleteObject(hBitmap);
DeleteDC(hdcCompatible);
ReleaseDC(NULL, hdcScreen);
return 0;
}
This is suggested to be used to analyze a pixel in an array.
int getPixelColor(int x, int y, int** pixels) {
return pixels[y][x];
}