Need an expert advice regarding GDI & C#
CodeGuru Home VC++ / MFC / C++ .NET / C# Visual Basic VB Forums Developer.com
Results 1 to 7 of 7

Thread: Need an expert advice regarding GDI & C#

Threaded View

  1. #1
    Join Date
    Jan 2010
    Posts
    5

    Unhappy Need an expert advice regarding GDI & C#

    Ok, here is the example.

    Why XORCycleA doesn't work while XORCycleB works...

    Here is quite serious riddle for an expert.

    Hope you can "speak" C# and will understand my strings without additional comments )

    XOR_Paint will be invoked each time you move the dialog window and smth overlays it.


    Code:
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Runtime.InteropServices;
    using System.Drawing;
    using System.Windows.Forms;
    using System.Drawing.Imaging;
    
    namespace ConsoleTestApplication
    {
     class Program
     {
     static void Main(string[] args)
     {
      new XOR().ShowDialog();
     }
     }
    
     internal class XOR : Form
     {
     [DllImport("gdi32.dll")]
     public static extern bool BitBlt(IntPtr hdcDest, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc,
                int nXSrc, int nYSrc, Int32 dwRop);
     [DllImport("gdi32.dll")]
     public static extern bool TextOut(IntPtr hdc, int x, int y, string lpString, int cbString);
    
     const Int32 SRCCOPY = 0x00CC0020;
     const Int32 SRCAND = 0x008800C6;
     const Int32 SRCINVERT = 0x00660046; // INVERT means XOR
    
     public XOR()
     {
      // Bit map created once with screen data in it
      bmA = new Bitmap(s.Width, s.Height, PixelFormat.Format32bppRgb);
      Graphics gfxBMP = Graphics.FromImage(bmA);
      gfxBMP.CopyFromScreen(0, 0, 0, 0, new Size(s.Width, s.Height), CopyPixelOperation.SourceCopy);
      gfxBMP.Dispose();
      this.Paint += new PaintEventHandler(XOR_Paint);
     }
    
     void XOR_Paint(object sender, PaintEventArgs e)
     {
      xorCycleA();
      xorCycleB();
     }
    
     Bitmap bmA;
     Size s = Screen.PrimaryScreen.Bounds.Size;
     unsafe void xorCycleA()
     {
      Graphics grfxScreen = Graphics.FromHwnd(IntPtr.Zero);
      Graphics grfxBitmap = Graphics.FromImage(bmA);
      bmA.Save(@"c:\before_xorA.bmp", ImageFormat.Bmp);
      IntPtr hdcBitmap = grfxBitmap.GetHdc();
      IntPtr hdcScreen = grfxScreen.GetHdc();
      // without any changes just copy screen data with XOR
      BitBlt(hdcBitmap, 0, 0, bmA.Width, bmA.Height, hdcScreen, 0, 0, SRCINVERT);
      grfxScreen.ReleaseHdc(hdcScreen);
      grfxBitmap.ReleaseHdc(hdcBitmap);
      grfxScreen.Dispose();
      grfxBitmap.Dispose();
      bmA.Save(@"c:\after_xorA.bmp", ImageFormat.Bmp);
     }
    
     Bitmap bmB;
     unsafe void xorCycleB()
     {
      Graphics grfxScreen = Graphics.FromHwnd(IntPtr.Zero);
      bmB = new Bitmap((int)grfxScreen.VisibleClipBounds.Width,
        (int)grfxScreen.VisibleClipBounds.Height, grfxScreen);
      Graphics grfxBitmap = Graphics.FromImage(bmB);
      bmB.Save(@"c:\before_xorB.bmp", ImageFormat.Bmp);
      IntPtr hdcBitmap = grfxBitmap.GetHdc();
      IntPtr hdcScreen = grfxScreen.GetHdc();
      BitBlt(hdcBitmap, 0, 0, bmB.Width, bmB.Height, hdcScreen, 0, 0, SRCCOPY);
      TextOut(hdcBitmap, 100, 100, "Hi, I'm here", 12);
      // comment BitBlt to make sure the bitmap contains screen data and the string on it inside after_xorB.bmp
      BitBlt(hdcBitmap, 0, 0, bmB.Width, bmB.Height, hdcScreen, 0, 0, SRCINVERT);
      grfxScreen.ReleaseHdc(hdcScreen);
      grfxBitmap.ReleaseHdc(hdcBitmap);
      grfxScreen.Dispose();
      grfxBitmap.Dispose();
      bmB.Save(@"c:\after_xorB.bmp", ImageFormat.Bmp);
     }
     }
    }
    Last edited by vitagoni; July 9th, 2011 at 12:26 PM.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Windows Mobile Development Center


Click Here to Expand Forum to Full Width

This is a CodeGuru survey question.


Featured


HTML5 Development Center