Microsoft Spy++ download: https://social.msdn.microsoft.com/Forums/vstudio/en-US/8d06750a-8d6c-4aca-9896-6ca49a631c07/where-can-i-get-microsoft-spy?forum=vcgeneral

https://ibb.co/ftUusf

Highlight flashes window borders - find which window handle is FFT spectrum analyzer

 

notsrccopy

https://ibb.co/nmBw50

C# code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }
        [DllImport("user32.dll")]
        public static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowDC(IntPtr hWnd);
        [DllImport("user32.dll")]
        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);

        [DllImport("gdi32.dll")]
        public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
        int nWidth, int nHeight, IntPtr hObjectSource, int nXSrc, int nYSrc, int dwRop);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth, int nHeight);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteObject(IntPtr hObject);
        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

        public Form1()
        {
            InitializeComponent();
        }

        private void button_GetGFX_Click(object sender, EventArgs e)
        {
            int i = Convert.ToInt32(textBox_Handle.Text, 16);
            IntPtr hwnd = new IntPtr(i);
            IntPtr hdcSrc = GetWindowDC(hwnd);
            RECT windowRect = new RECT();
            GetWindowRect(hwnd, ref windowRect);
            int w = windowRect.right - windowRect.left;
            int h = windowRect.bottom - windowRect.top;
            IntPtr hdcDest = CreateCompatibleDC(hdcSrc);
            IntPtr hBitmap = CreateCompatibleBitmap(hdcSrc, w, h);
            IntPtr hOld = SelectObject(hdcDest, hBitmap);
            BitBlt(hdcDest, 0, 0, w, h, hdcSrc, 0, 0, 0x00330008); // notsrccopy
            SelectObject(hdcDest, hOld);
            DeleteDC(hdcDest);
            ReleaseDC(hwnd, hdcSrc);
            pictureBox_Img.Image = Image.FromHbitmap(hBitmap);
            DeleteObject(hBitmap);
            var encoder = ImageCodecInfo.GetImageEncoders().First(c => c.FormatID == ImageFormat.Jpeg.Guid);
            var encParams = new EncoderParameters(1);
            encParams.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 60L);
            pictureBox_Img.Image.Save(@"c:\temp\sa.jpg", encoder, encParams);
        }
    }
}