How to get Bitmap from CreateCompatibleBitmap?

Question

I want to capture the screen to bitmap.

[DllImport("gdi32.dll")]
public extern static IntPtr CreateCompatibleDC(IntPtr hdc);
[DllImport("gdi32.dll")]
public extern static IntPtr CreateCompatibleBitmap(IntPtr hdc, Int32 width, Int32 height);
var hdc = CreateCompatibleDC(0);
var bitmap = CreateCompatibleBitmap(GetDC(0), 1920, 1080);
SelectObject(hdc, bitmap);
BitBlt(hdc, 0, 0, 0, 0, GetDC(0), 1920, 1080, 0);

and then how to get bitmap from bitmap?

Answer 1

Hi,@mc . Welcome to Microsoft Q&A Forum.

To capture the screen to a bitmap in C# using the GDI functions, you can follow the steps you've outlined. However, after capturing the screen to a device context (HDC), you could copy it into a .NET Bitmap object for further manipulation.

To display a Bitmap in a WPF application, you can use the System.Windows.Controls.Image control. You'll need to convert the Bitmap to a WPF BitmapSource first.

 <StackPanel Name="stackPanel">
        <Button Content="capture" Click="Button_Click"/>
    </StackPanel>

Codebehind:

using System;

using System.Drawing;

using System.Runtime.InteropServices;

using System.Windows;

using System.Windows.Interop;

using System.Windows.Media.Imaging;

using Image = System.Drawing.Image;


public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        [DllImport("gdi32.dll")]
        public extern static IntPtr CreateCompatibleDC(IntPtr hdc);

        [DllImport("gdi32.dll")]
        public extern static IntPtr CreateCompatibleBitmap(IntPtr hdc, int width, int height);

        [DllImport("gdi32.dll")]
        public extern static IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

        [DllImport("gdi32.dll")]
        public extern static int BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, int dwRop);

        [DllImport("user32.dll")]
        public static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("user32.dll")]
        public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern int DeleteObject(IntPtr hObject);

        public static Bitmap CaptureScreen(int width, int height)
        {
            IntPtr hdc = GetDC(IntPtr.Zero);
            IntPtr hdcMem = CreateCompatibleDC(hdc);
            IntPtr hBitmap = CreateCompatibleBitmap(hdc, width, height);
            SelectObject(hdcMem, hBitmap);
            BitBlt(hdcMem, 0, 0, width, height, hdc, 0, 0, 0x00CC0020); // SRCCOPY

            Bitmap bitmap = Image.FromHbitmap(hBitmap);
            DeleteObject(hBitmap);
            ReleaseDC(IntPtr.Zero, hdc);
            DeleteObject(hdcMem);

            return bitmap;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            int screenWidth = 1920;  // Your screen width
            int screenHeight = 1080; // Your screen height

            Bitmap screenCapture = CaptureScreen(screenWidth, screenHeight);

         
            BitmapSource bitmapSource = ConvertBitmapToBitmapSource(screenCapture);

            System.Windows.Controls.Image imageControl = new System.Windows.Controls.Image();
            imageControl.Source = bitmapSource;

            stackPanel.Children.Add(imageControl);

        }

        public static BitmapSource ConvertBitmapToBitmapSource(Bitmap bitmap)
        {
            IntPtr hBitmap = bitmap.GetHbitmap();
            BitmapSource bitmapSource = Imaging.CreateBitmapSourceFromHBitmap(hBitmap, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());
            DeleteObject(hBitmap);
            return bitmapSource;
        }

       
     
    }

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