Been losing some days on this, I'm trying to capture an specific part of a hidden window, like per example, capture only coordinates 300, 300 to 350, 350. I'm trying to do some image recognition and using a full screenshot takes too long to find matches. Below is the code I'm using to capture a region:
public class WindowCapture
{
private class User32
{
[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 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("user32.dll")]
public static extern bool PrintWindow(IntPtr hWnd, IntPtr hDC, uint nFlags);
}
private class GDI32
{
public const int SRCCOPY = 0x00CC0020;
[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 Image CaptureWindowRegion(IntPtr hWnd, int x, int y, int w, int h)
{
IntPtr hdcSrc = User32.GetWindowDC(hWnd);
User32.RECT windowRect = new User32.RECT();
User32.GetWindowRect(hWnd, ref windowRect);
int originalwidth = windowRect.right - windowRect.left;
int originalheight = windowRect.bottom - windowRect.top;
CropRect(ref windowRect, x, y, w, h);
int width = windowRect.right - windowRect.left;
int height = windowRect.bottom - windowRect.top;
IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, originalwidth, originalheight);
IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
User32.PrintWindow(hWnd, hdcDest, 0);
IntPtr hdcDest2 = GDI32.CreateCompatibleDC(hdcDest);
IntPtr hBitmap2 = GDI32.CreateCompatibleBitmap(hdcDest, width, height);
IntPtr hOld2 = GDI32.SelectObject(hdcDest2, hBitmap2);
GDI32.BitBlt(hdcDest2, 0, 0, width, height, hdcDest, x, y, GDI32.SRCCOPY);
GDI32.SelectObject(hdcDest, hOld);
GDI32.SelectObject(hdcDest2, hOld2);
GDI32.DeleteDC(hdcDest);
GDI32.DeleteDC(hdcDest2);
User32.ReleaseDC(hWnd, hdcSrc);
Image img = Image.FromHbitmap(hBitmap2);
GDI32.DeleteObject(hBitmap);
GDI32.DeleteObject(hBitmap2);
return img;
}
private static void CropRect(ref User32.RECT windowRect, int x, int y, int w, int h)
{
windowRect.left = (x > 0) ? Math.Min(windowRect.right, windowRect.left + x) : windowRect.left;
windowRect.right = (w > 0) ? Math.Min(windowRect.right, windowRect.left + w) : windowRect.right;
windowRect.top = (y > 0) ? Math.Min(windowRect.bottom, windowRect.top + y) : windowRect.top;
windowRect.bottom = (h > 0) ? Math.Min(windowRect.bottom, windowRect.top + h) : windowRect.bottom;
}
}
After researching a bunch, all I could manage was a smaller all black bitmap.
Any idea on how this could be done?
Related
Purpose: Mirror a window of an external process by capturing images from this window and presenting the images in a picturebox using a timer.
Problem: When my application is in focus, everything happens fine! But if I switch the focus to the other window (not from my application), the picturebox stops refreshing the images. When I focus on my application again, everything returns to normal.
Limitation: I need the picturebox to continue updating even though my application is in the background.
Timer to capture images and show in picturebox:
private void timer_picBOX_refresh_Tick(object sender, EventArgs e)
{
pictureBox1.BackgroundImage = PrintScreen.CaptureWindow(GAME_MainHandle);
pictureBox1.Refresh();
}
Class to capture specific window:
public class class_ScreenCapture
{
public Image CaptureScreen()
{
return CaptureWindow(User32.GetDesktopWindow());
}
/// <summary>
/// Creates an Image object containing a screen shot of a specific window
/// </summary>
public Image CaptureWindow(IntPtr handle, int imgX = 0, int imgY = 0, int largura = 0, int altura = 0)
{
// get te hDC of the target window
IntPtr hdcSrc = User32.GetWindowDC(handle);
// get the size
User32.RECT windowRect = new User32.RECT();
User32.GetWindowRect(handle, ref windowRect);
if (largura == 0 || altura == 0)
{
largura = windowRect.right - windowRect.left;
altura = windowRect.bottom - windowRect.top;
}
// create a device context we can copy to
IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
// create a bitmap we can copy it to,
// using GetDeviceCaps to get the width/height
IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, largura, altura);
// select the bitmap object
IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
// bitblt over
GDI32.BitBlt(hdcDest, 0, 0, largura, altura, hdcSrc, imgX, imgY, GDI32.SRCCOPY);
// restore selection
GDI32.SelectObject(hdcDest, hOld);
// clean up
GDI32.DeleteDC(hdcDest);
User32.ReleaseDC(handle, hdcSrc);
// get a .NET image object for it
Image img = Image.FromHbitmap(hBitmap);
// free up the Bitmap object
GDI32.DeleteObject(hBitmap);
return img;
}
/// <summary>
/// Helper class containing Gdi32 API functions
/// </summary>
private class GDI32
{
public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
[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);
}
/// <summary>
/// Helper class containing User32 API functions
/// </summary>
private class User32
{
[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);
}
}
Test it.
private void timer_picBOX_refresh_Tick(object sender, EventArgs e)
{
pictureBox1.Image = PrintScreen.CaptureWindow(GAME_MainHandle);
pictureBox1.Refresh();
Refresh();
}
I downloaded a class with handy methods that I use to take screenshots of other programs for a while now
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
namespace EmulatorObserver.model
{
/// <summary>
/// Provides functions to capture the entire screen, or a particular window, and save it to a file.
/// </summary>
public static class ScreenCapture
{
/// <summary>
/// Creates an Image object containing a screen shot of a specific window
/// </summary>
/// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
/// <returns></returns>
public static Bitmap CaptureWindow(IntPtr handle)
{
// get te hDC of the target window
IntPtr hdcSrc = GetWindowDC(handle);
// get the size
RECT windowRect = new RECT();
GetWindowRect(handle, ref windowRect);
int width = windowRect.right - windowRect.left;
int height = windowRect.bottom - windowRect.top;
// create a device context we can copy to
IntPtr hdcDest = CreateCompatibleDC(hdcSrc);
// create a bitmap we can copy it to,
// using GetDeviceCaps to get the width/height
IntPtr hBitmap = CreateCompatibleBitmap(hdcSrc, width, height);
// select the bitmap object
IntPtr hOld = SelectObject(hdcDest, hBitmap);
// bitblt over
BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, SRCCOPY);
// restore selection
SelectObject(hdcDest, hOld);
// clean up
DeleteDC(hdcDest);
ReleaseDC(handle, hdcSrc);
// get a .NET image object for it
Bitmap raw;
using(Image img = Image.FromHbitmap(hBitmap))
{
raw = (Bitmap)img.Clone();
}
// free up the Bitmap object
DeleteObject(hBitmap);
return raw;
}
////////////////////////////////////////////////////////////////////////////////////////////
// Win32 API
[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
public int left;
public int top;
public int right;
public int bottom;
}
public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
[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("user32.dll")]
public static extern IntPtr GetWindowDC(IntPtr hWnd);
[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);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth, int nHeight);
[DllImport("user32.dll")]
public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
}
}
so far it worked nicely, but when trying to take a screenshot of an Android emulator MEmu
the resulting picture looks like this
what can I not take a screenshot of the content by running 'ScreenCapture.CaptureWindow(h).Save(#"screenshot.bmp");' ? what way do I have to (quickly) get these pictures?
I found out, that there is a static property in the System.Windows.SystemParameters class that declares the color the user chose for his Windows overall.
But there is a second possibility for the user that enables him to enable or disable, whether the taskbar/windows bar should use that same color.
I was unable to find a key for that in the SystemParameters-class.
I believe there is a registry value to find the colour and it is probably inside:
HKEY_CURRENT_USER\Control Panel\Colors
However on my system I have colours on the taskbar disabled and that colour value doesn't seem to appear in this key.
A work around would be to combine the answers to the following two questions:
TaskBar Location
How to Read the Colour of a Screen Pixel
You need the following imports:
[DllImport("shell32.dll")]
private static extern IntPtr SHAppBarMessage(int msg, ref APPBARDATA data);
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
private static extern int BitBlt(IntPtr hDC, int x, int y, int nWidth, int nHeight, IntPtr hSrcDC, int xSrc, int ySrc, int dwRop);
The following structs:
private struct APPBARDATA
{
public int cbSize;
public IntPtr hWnd;
public int uCallbackMessage;
public int uEdge;
public RECT rc;
public IntPtr lParam;
}
private struct RECT
{
public int left, top, right, bottom;
}
And the following constant:
private const int ABM_GETTASKBARPOS = 5;
Then you can call the following two methods:
public static Rectangle GetTaskbarPosition()
{
APPBARDATA data = new APPBARDATA();
data.cbSize = Marshal.SizeOf(data);
IntPtr retval = SHAppBarMessage(ABM_GETTASKBARPOS, ref data);
if (retval == IntPtr.Zero)
{
throw new Win32Exception("Please re-install Windows");
}
return new Rectangle(data.rc.left, data.rc.top, data.rc.right - data.rc.left, data.rc.bottom - data.rc.top);
}
public static Color GetColourAt(Point location)
{
using (Bitmap screenPixel = new Bitmap(1, 1, PixelFormat.Format32bppArgb))
using (Graphics gdest = Graphics.FromImage(screenPixel))
{
using (Graphics gsrc = Graphics.FromHwnd(IntPtr.Zero))
{
IntPtr hSrcDC = gsrc.GetHdc();
IntPtr hDC = gdest.GetHdc();
int retval = BitBlt(hDC, 0, 0, 1, 1, hSrcDC, location.X, location.Y, (int)CopyPixelOperation.SourceCopy);
gdest.ReleaseHdc();
gsrc.ReleaseHdc();
}
return screenPixel.GetPixel(0, 0);
}
}
Like this:
Color taskBarColour = GetColourAt(GetTaskbarPosition().Location);
I'm trying to Capture an Image from a window given the Handle/DC. I want to capture the Image with all the transparency and pixels so I decided I'd use GDI/GDI+.
The below code is what I have, but when it "writes" the bitmap, it writes it wrong :S In other words, the file is unreadable. It is blank. Yet it is 20kb in size :S
Any ideas what is wrong?
Imports.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
namespace Imaging
{
static class Imports
{
public enum ObjectType : uint
{
OBJ_PEN = 1,
OBJ_BRUSH = 2,
OBJ_DC = 3,
OBJ_METADC = 4,
OBJ_PAL = 5,
OBJ_FONT = 6,
OBJ_BITMAP = 7,
OBJ_REGION = 8,
OBJ_METAFILE = 9,
OBJ_MEMDC = 10,
OBJ_EXTPEN = 11,
OBJ_ENHMETADC = 12,
OBJ_ENHMETAFILE = 13
}
public enum TernaryRasterOperations : uint
{
SRCCOPY = 0x00CC0020,
SRCPAINT = 0x00EE0086,
SRCAND = 0x008800C6,
SRCINVERT = 0x00660046,
SRCERASE = 0x00440328,
NOTSRCCOPY = 0x00330008,
NOTSRCERASE = 0x001100A6,
MERGECOPY = 0x00C000CA,
MERGEPAINT = 0x00BB0226,
PATCOPY = 0x00F00021,
PATPAINT = 0x00FB0A09,
PATINVERT = 0x005A0049,
DSTINVERT = 0x00550009,
BLACKNESS = 0x00000042,
WHITENESS = 0x00FF0062,
CAPTUREBLT = 0x40000000
}
[StructLayout(LayoutKind.Sequential)]
public struct Rect
{
public int Left, Top, Right, Bottom;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct BITMAPFILEHEADER
{
public ushort bfType;
public uint bfSize;
public ushort bfReserved1;
public ushort bfReserved2;
public uint bfOffBits;
}
[StructLayout(LayoutKind.Sequential)]
public struct BITMAPINFOHEADER
{
public uint biSize;
public int biWidth;
public int biHeight;
public ushort biPlanes;
public ushort biBitCount;
public uint biCompression;
public uint biSizeImage;
public int biXPelsPerMeter;
public int biYPelsPerMeter;
public uint biClrUsed;
public uint biClrImportant;
public void Init()
{
biSize = (uint)Marshal.SizeOf(this);
}
}
[StructLayout(LayoutKind.Sequential)]
public struct BITMAPINFO
{
public uint biSize;
public int biWidth;
public int biHeight;
public ushort biPlanes;
public ushort biBitCount;
public uint biCompression;
public uint biSizeImage;
public int biXPelsPerMeter;
public int biYPelsPerMeter;
public uint biClrUsed;
public uint biClrImportant;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public uint[] cols;
}
[StructLayout(LayoutKind.Sequential)]
public struct BITMAP
{
public int bmType;
public int bmWidth;
public int bmHeight;
public int bmWidthBytes;
public ushort bmPlanes;
public ushort bmBitsPixel;
public IntPtr bmBits;
};
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
[DllImport("user32.dll")]
public static extern IntPtr GetDC(IntPtr WindowHandle);
[DllImport("user32.dll")]
public static extern void ReleaseDC(IntPtr WindowHandle, IntPtr DC);
[DllImport("user32.dll")]
public static extern IntPtr GetWindowRect(IntPtr WindowHandle, ref Rect rect);
[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool PrintWindow(IntPtr hwnd, IntPtr DC, uint nFlags);
[DllImport("user32.dll")]
public static extern int SetForegroundWindow(IntPtr hWnd);
[DllImport("user32.dll")]
public static extern IntPtr ShowWindow(IntPtr hWnd, int nCmdShow);
[DllImport("user32.dll")]
public static extern int GetWindowRgn(IntPtr hWnd, IntPtr hRgn);
[DllImport("gdi32.dll")]
public static extern IntPtr GetCurrentObject(IntPtr DC, ObjectType uObjectType);
[DllImport("gdi32.dll")]
public static extern int GetObject(IntPtr hObject, int nCount, ref BITMAP lpObject);
[DllImport("gdi32.dll", SetLastError = true)]
public static extern IntPtr CreateCompatibleDC(IntPtr DC);
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
public static extern bool DeleteDC(IntPtr DC);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleBitmap(IntPtr DC, int nWidth, int nHeight);
[DllImport("gdi32.dll", ExactSpelling = true, PreserveSig = true, SetLastError = true)]
public static extern IntPtr SelectObject(IntPtr DC, IntPtr hgdiobj);
[DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect, int nBottomRect);
[DllImport("gdi32.dll")]
static extern bool FillRgn(IntPtr DC, IntPtr hrgn, IntPtr hbr);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateSolidBrush(uint crColor);
[DllImport("gdi32.dll")]
public static extern int GetDIBits(IntPtr DC, IntPtr hbmp, uint uStartScan, uint cScanLines, [Out] byte[] lpvBits, ref BITMAPINFO lpbmi, uint uUsage);
[DllImport("gdi32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool BitBlt(IntPtr DC, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr SrcDC, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);
}
}
My PBitmap class:
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;
namespace Imaging
{
class PBitmap
{
private Bitmap Img = null;
private Imports.BITMAPINFO Info;
private Imports.BITMAPFILEHEADER bFileHeader;
public PBitmap(IntPtr Window, int X, int Y, uint BitsPerPixel = 24)
{
IntPtr DC = Imports.GetDC(Window);
Imports.BITMAP Bmp = new Imports.BITMAP();
IntPtr hBmp = Imports.GetCurrentObject(DC, Imports.ObjectType.OBJ_BITMAP);
if (Imports.GetObject(hBmp, Marshal.SizeOf(Bmp), ref Bmp) == 0)
throw new Exception("ERROR_INVALID_WINDOW_HANDLE.");
Imports.Rect BMBox = new Imports.Rect();
Imports.GetWindowRect(Window, ref BMBox); //GetClientRect
int width = BMBox.Right - BMBox.Left;
int height = BMBox.Bottom - BMBox.Top;
IntPtr MemDC = Imports.GetDC(IntPtr.Zero);
IntPtr SDC = Imports.CreateCompatibleDC(MemDC);
IntPtr hSBmp = Imports.CreateCompatibleBitmap(MemDC, width, height);
Imports.DeleteObject(Imports.SelectObject(SDC, hSBmp));
Imports.BitBlt(SDC, 0, 0, width, height, DC, X, Y, Imports.TernaryRasterOperations.SRCCOPY);
long size = ((width * BitsPerPixel + 31) / 32) * 4 * height;
Info = new Imports.BITMAPINFO();
bFileHeader = new Imports.BITMAPFILEHEADER();
Info.biSize = (uint)Marshal.SizeOf(Info);
Info.biWidth = width;
Info.biHeight = height;
Info.biPlanes = 1;
Info.biBitCount = (ushort)BitsPerPixel;
Info.biCompression = 0;
Info.biSizeImage = (uint)size;
bFileHeader.bfType = 0x4D42;
bFileHeader.bfOffBits = (uint)(Marshal.SizeOf(bFileHeader) + Marshal.SizeOf(Info));
bFileHeader.bfSize = (uint)(bFileHeader.bfOffBits + size);
byte[] ImageData = new byte[size];
Imports.GetDIBits(SDC, hSBmp, 0, (uint)height, ImageData, ref Info, 0);
var bw = new BinaryWriter(File.Open("C:/Users/*******/Desktop/Foo.bmp", FileMode.OpenOrCreate));
bw.Write((short)0x4D42);
bw.Write((uint)(bFileHeader.bfOffBits + size));
bw.Write((uint)0);
bw.Write((uint)54);
bw.Write((uint)Info.biSize);
bw.Write(width);
bw.Write(height);
bw.Write((short)Info.biPlanes);
bw.Write(BitsPerPixel);
bw.Write((uint)0);
bw.Write((uint)size);
bw.Write((uint)0);
bw.Write((uint)0);
bw.Write((uint)0);
bw.Write((uint)0);
bw.Write(ImageData);
bw.Flush();
bw.Close();
bw.Dispose();
Imports.DeleteDC(SDC);
Imports.DeleteObject(hSBmp);
Imports.ReleaseDC(IntPtr.Zero, MemDC);
Imports.ReleaseDC(Window, DC);
}
}
}
If you're looking for a quick band-aid fix to get this done (it just needs to work, not used often, etc) consider just loading the image back into .NET and re-saving it with PNG compression enabled. The .NET framework will handle this for you and the file size will be a lot more optimal. Of course, if this is for a real-time application this isn't ideal.
I am trying to capture the content of the WebBrowser control. DrawToBitmap() would work perfectly, but it is not supported in documentation for the WebBrowser control. I have been trying to find another way to capture the contents of the WebBrowser control and save them to a local image file.
Does anyone have any workarounds or other methods to save the contents of the WebBrowser control to a local image file?
The Control.DrawToBitmap doesn't always work so I resorted to the following native API calls that provide more consistent results:
The Utilities class. Call Utilities.CaptureWindow(Control.Handle) to capture a specific control:
public static class Utilities
{
public static Image CaptureScreen()
{
return CaptureWindow(User32.GetDesktopWindow());
}
public static Image CaptureWindow(IntPtr handle)
{
IntPtr hdcSrc = User32.GetWindowDC(handle);
RECT windowRect = new RECT();
User32.GetWindowRect(handle, ref windowRect);
int width = windowRect.right - windowRect.left;
int height = windowRect.bottom - windowRect.top;
IntPtr hdcDest = Gdi32.CreateCompatibleDC(hdcSrc);
IntPtr hBitmap = Gdi32.CreateCompatibleBitmap(hdcSrc, width, height);
IntPtr hOld = Gdi32.SelectObject(hdcDest, hBitmap);
Gdi32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, ApiConstants.SRCCOPY);
Gdi32.SelectObject(hdcDest, hOld);
Gdi32.DeleteDC(hdcDest);
User32.ReleaseDC(handle, hdcSrc);
Image image = Image.FromHbitmap(hBitmap);
Gdi32.DeleteObject(hBitmap);
return image;
}
}
The Gdi32 class:
public class Gdi32
{
[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);
}
The User32 class:
public static class User32
{
[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 GetWindowRect(IntPtr hWnd, ref RECT rect);
[DllImport("user32.dll")]
public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
}
The constants used:
public const int SRCCOPY = 13369376;
The structs used:
[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
public int left;
public int top;
public int right;
public int bottom;
}
A friendly Control extension method:
public static class ControlExtensions
{
public static Image DrawToImage(this Control control)
{
return Utilities.CaptureWindow(control.Handle);
}
}
This is a code snippet from my CC.Utilities project and I specifically wrote it to take screenshots from the WebBrowser control.
The following method can capture the entire window image even if the window is larger than the size of screen. Then it can capture the image of the contents of the page if the window be resized to the webBrowser.Document.OffsetRectangle.Size
class NativeMethods
{
[ComImport]
[Guid("0000010D-0000-0000-C000-000000000046")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IViewObject
{
void Draw([MarshalAs(UnmanagedType.U4)] uint dwAspect, int lindex, IntPtr pvAspect, [In] IntPtr ptd, IntPtr hdcTargetDev, IntPtr hdcDraw, [MarshalAs(UnmanagedType.Struct)] ref RECT lprcBounds, [In] IntPtr lprcWBounds, IntPtr pfnContinue, [MarshalAs(UnmanagedType.U4)] uint dwContinue);
}
[StructLayout(LayoutKind.Sequential, Pack = 4)]
struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
}
public static void GetImage(object obj, Image destination, Color backgroundColor)
{
using(Graphics graphics = Graphics.FromImage(destination))
{
IntPtr deviceContextHandle = IntPtr.Zero;
RECT rectangle = new RECT();
rectangle.Right = destination.Width;
rectangle.Bottom = destination.Height;
graphics.Clear(backgroundColor);
try
{
deviceContextHandle = graphics.GetHdc();
IViewObject viewObject = obj as IViewObject;
viewObject.Draw(1, -1, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, deviceContextHandle, ref rectangle, IntPtr.Zero, IntPtr.Zero, 0);
}
finally
{
if(deviceContextHandle != IntPtr.Zero)
{
graphics.ReleaseHdc(deviceContextHandle);
}
}
}
}
}
Usage :
Bitmap screenshot = new Bitmap(1024, 768);
NativeMethods.GetImage(webBrowser.ActiveXInstance, screenshot, Color.White);
I am using DrawToBitmap (Visual Studio 2008 C#) to capture big images (user signed invoices,content out of the screen). Basically it is working well but I am getting blank images. About 100 employees are using this software, about every 2 weeks I can see one blank image.
I have done a lot of testing and one funny thing I found is:
I created a button to generate the image from the webbrowser. Usually is OK but if I click the webbrowser first, then click the create-button, the blank image will appear.
I used OleDraw method as in this topic on SO, but integrated it in a class derived from WebBrowser. This allows to do normal Control.DrawToBitmap not only for the WebBrowser, but for a form with WebBrowser in it as well. This also works if the form is hidden (covered by another form, including MDI parent form) and should work when user has locked session with Win+L (I haven't tested it).
public class WebBrowserEx : WebBrowser
{
private const uint DVASPECT_CONTENT = 1;
[DllImport("ole32.dll", PreserveSig = false)]
private static extern void OleDraw([MarshalAs(UnmanagedType.IUnknown)] object pUnk,
uint dwAspect,
IntPtr hdcDraw,
[In] ref System.Drawing.Rectangle lprcBounds
);
protected override void WndProc(ref Message m)
{
const int WM_PRINT = 0x0317;
switch (m.Msg)
{
case WM_PRINT:
Rectangle browserRect = new Rectangle(0, 0, this.Width, this.Height);
// Don't know why, but drawing with OleDraw directly on HDC from m.WParam.
// results in badly scaled (stretched) image of the browser.
// So, drawing to an intermediate bitmap first.
using (Bitmap browserBitmap = new Bitmap(browserRect.Width, browserRect.Height))
{
using (var graphics = Graphics.FromImage(browserBitmap))
{
var hdc = graphics.GetHdc();
OleDraw(this.ActiveXInstance, DVASPECT_CONTENT, hdc, ref browserRect);
graphics.ReleaseHdc(hdc);
}
using (var graphics = Graphics.FromHdc(m.WParam))
{
graphics.DrawImage(browserBitmap, Point.Empty);
}
}
// ignore default WndProc
return;
}
base.WndProc(ref m);
}
}