Jump to content
  • Advertisement
Sign in to follow this  
alkisbkn

OpenGL Capturing screen and creating an opengl texture

This topic is 3202 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hello, for the purpose of my game, I need to capture the entire screen and generate an opengl texture out of it. Currently, I am using GDI to do the work, the code is as follows: (sorry for the length of the code, but I think you need to see what's happening, I explain what I am doing after the code block.)
HBITMAP DesktopCapturer::captureScreen()
{

	HDC         hScrDC, hMemDC;         // screen DC and memory DC     
	int         nX, nY, nX2, nY2;       // coordinates of rectangle to grab     
	int         nWidth, nHeight;        // DIB width and height     
	int         xScrn, yScrn;           // screen resolution      

	HGDIOBJ     hOldBitmap , hBitmap;
		
   // create a DC for the screen and create     
   // a memory DC compatible to screen DC          

   hScrDC = CreateDC("DISPLAY", NULL, NULL, NULL);     
   hMemDC = CreateCompatibleDC(hScrDC);      // get points of rectangle to grab  
   
   DisplayMode desktop = Graphics().GetDesktopDisplayMode();

   nX = 0;
   nY = 0;
   nX2 = desktop.Width;
   nY2 = desktop.Height;
   
   nWidth = nX2 - nX;     
   nHeight = nY2 - nY;      
   
   // create a bitmap compatible with the screen DC     
   
   hBitmap = CreateCompatibleBitmap(hScrDC, nWidth, nHeight);      
   
   // select new bitmap into memory DC     
   
   hOldBitmap =   SelectObject (hMemDC, hBitmap);      
   
   // bitblt screen DC to memory DC     
   
   BitBlt(hMemDC, 0, 0, nWidth, nHeight, hScrDC, nX, nY, SRCCOPY | CAPTUREBLT);     
   
   // select old bitmap back into memory DC and get handle to     
   // bitmap of the screen          
   
   hBitmap = SelectObject(hMemDC, hOldBitmap);      
   
   // clean up      
   
   DeleteDC(hScrDC);     
   DeleteDC(hMemDC);      
   
   // return handle to the bitmap      
   
   return (HBITMAP)hBitmap; 
}

bool DesktopCapturer::convertToDib(HBITMAP &hBitmap)
{
	bool bConverted = false;
  BITMAP stBitmap;
  if (GetObject(hBitmap, sizeof(stBitmap), 
            &stBitmap) && !stBitmap.bmBits)
  {
    // that is a DFB. Now we attempt to create

    // a DIB with the same sizes and pixel format.

    HDC hScreen = GetDC(NULL);
    if (hScreen)
    {
      union {
        BITMAPINFO stBitmapInfo;
        BYTE pReserveSpace[sizeof(BITMAPINFO) 
                     + 0xFF * sizeof(RGBQUAD)];
      };
      ZeroMemory(pReserveSpace, sizeof(pReserveSpace));
      stBitmapInfo.bmiHeader.biSize = sizeof(stBitmapInfo.bmiHeader);
      stBitmapInfo.bmiHeader.biWidth = stBitmap.bmWidth;
      stBitmapInfo.bmiHeader.biHeight = stBitmap.bmHeight;
      stBitmapInfo.bmiHeader.biPlanes = 1;
      stBitmapInfo.bmiHeader.biBitCount = stBitmap.bmBitsPixel;
      stBitmapInfo.bmiHeader.biCompression = BI_RGB;

      if (stBitmap.bmBitsPixel <= 8)
      {
        stBitmapInfo.bmiHeader.biClrUsed = 
                        1 << stBitmap.bmBitsPixel;
        // This image is paletted-managed.

        // Hence we have to synthesize its palette.

      }
      stBitmapInfo.bmiHeader.biClrImportant = 
                       stBitmapInfo.bmiHeader.biClrUsed;

      PVOID pBits;
      HBITMAP hDib = CreateDIBSection(hScreen, 
        &stBitmapInfo, DIB_RGB_COLORS, &pBits, NULL, 0);

      if (hDib)
      {
        // ok, we're lucky. Now we have

        // to transfer the image to the DFB.

        HDC hMemSrc = CreateCompatibleDC(NULL);
        if (hMemSrc)
        {
          HGDIOBJ hOldSrc = SelectObject(hMemSrc, hBitmap);
          if (hOldSrc)
          {
            HDC hMemDst = CreateCompatibleDC(NULL);
            if (hMemDst)
            {
              HGDIOBJ hOldDst = SelectObject(hMemDst, hDib);
              if (hOldDst)
              {
                if (stBitmap.bmBitsPixel <= 8)
                {
                  // take the DFB's palette and set it to our DIB

                  HPALETTE hPalette = 
                    (HPALETTE) GetCurrentObject(hMemSrc, OBJ_PAL);
                  if (hPalette)
                  {
                    PALETTEENTRY pPaletteEntries[0x100];
                    UINT nEntries = GetPaletteEntries(hPalette, 
                                    0, stBitmapInfo.bmiHeader.biClrUsed, 
                                    pPaletteEntries);
                    if (nEntries)
                    {
                      
                      for (UINT nIndex = 0; nIndex < nEntries; nIndex++)
                        pPaletteEntries[nEntries].peFlags = 0;
                      SetDIBColorTable(hMemDst, 0, 
                        nEntries, (RGBQUAD*) pPaletteEntries) == nEntries;

                    }
                  }
                }

                // transfer the image using BitBlt function.

                // It will probably end in the

                // call to driver's DrvCopyBits function.

                if (BitBlt(hMemDst, 0, 0, stBitmap.bmWidth, 
                      stBitmap.bmHeight, hMemSrc, 0, 0, SRCCOPY))
                  bConverted = true; // success


                SelectObject(hMemDst, hOldDst);
              }
              DeleteDC(hMemDst);
            }
            SelectObject(hMemSrc, hOldSrc);
          }
          DeleteDC(hMemSrc);
        }

        if (bConverted)
        {
          DeleteObject(hBitmap); // it's no longer needed

          hBitmap = hDib;
        }
        else
          DeleteObject(hDib);
      }
      ReleaseDC(NULL, hScreen);
    }
  }
  return bConverted;

}

void DesktopCapturer::Init()
{
        gdi_bitmap = captureScreen();

	convertToDib (gdi_bitmap);
	GetObject (gdi_bitmap, sizeof(BITMAP), &gdi_bitmap_data);

	data_size = gdi_bitmap_data.bmWidth * gdi_bitmap_data.bmHeight * 4;
	// convert from BGR to RGB:
	for (int i=0; i<data_size; i+=4)
	{
		unsigned char tmp = ((unsigned char*)gdi_bitmap_data.bmBits);
		((unsigned char*)gdi_bitmap_data.bmBits) = ((unsigned char*)gdi_bitmap_data.bmBits)[i+2];
		((unsigned char*)gdi_bitmap_data.bmBits)[i+2] = tmp;

	}
}
What the above code does is to take a screenshot of the whole screen, convert it to DIB format, and use this DIB BITMAP for generating a texture from the bmBits field. Before creating the texture, I convert the BGRA to RGBA for use with SOIL. The method called to capture the desktop is "Init", at the program start. After that, I use SOIL library to create an opengl texture from the bmBits member of the gdi_bitmap_data, which works excellent on my 2 Windows 7 machines. The problem comes when I run the program on Windows XP SP3, with an 9800GT. Given the fact that the texture loading happens correctly in both cases, I think it's something to do with the GDI capture code. Here is a screenshot of the problem. You see that not all the colours are displayed. More importantly, it seems that only the icons are captured, the rest is black, as I see it. problematic: Free Image Hosting at www.ImageShack.us normal desktop: Free Image Hosting at www.ImageShack.us And here is a working screenshot, from a Windows 7 system (GMA950). Free Image Hosting at www.ImageShack.us That's it, I am sorry for the post length again. I hope you can help me out here. Thank you

Share this post


Link to post
Share on other sites
Advertisement
Just look at the color of the Quicktime icon. It used to be blue but in your crapped version its orange. That leads me to the assumption that you store the pixels in a different order such as ARGB written to RGBA without changing the color layout. Hence you most likely screw the alpha value and get a black color due to either OpenGL color blending settings or the mixed up pixel color is just this black color.

Make sure you read and store the RGBA color components in the necessary formats.

Share this post


Link to post
Share on other sites
Could the capturing mode using the above GDI method produce different pixel formats in different systems?
If so, how can I check that and make the correct conversions?

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Tags

  • Similar Content

    • By McGrane
      Hey
      My laptop recently decided to die, so Ive been transferring my project to my work laptop just to get it up to date, and commit it. I was banging my head against the wall all day, as my textures where not displaying in my program- I was getting no errors and no indication of why it was occurring so I have been just trying to figure it out- I know the image loading was working ok, as im using image data elsewhere, I was pretty confident that the code was fine also, as ive never had an issue with displaying textures before, so I thought it might be the drivers on this laptop, (my old one was just using the built in IntelHD, while this laptop has a NVIDIA graphics card) but all seems to be up to date.
      Below are my basic shaders:
      Vertex Shader
      #version 330 core layout(location = 0) in vec3 position; layout(location = 1) in vec3 color; layout(location = 2) in vec3 normal; layout(location = 3) in vec2 texCoord; uniform mat4 Projection; uniform mat4 Model; out vec3 Color; out vec3 Normal; out vec2 TexCoord; void main() { gl_Position = Projection * Model * vec4( position, 1.0 ); Color = color; Normal = normal; TexCoord = vec2( texCoord.x, texCoord.y); } Fragment Shader
      #version 330 core in vec3 Color; in vec3 Normal; in vec2 TexCoord; uniform sampler2D textureData; void main() { vec4 textureColor = texture( textureData, TexCoord ); vec4 finalColor = textureColor * vec4( Color, 1.0f); gl_FragColor = finalColor; } Calling Code
      glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, textureID); glUniform1i(glGetUniformLocation(shaderID, "textureData"), textureID); Now this is the part i dont understand, I worked through my program, until I got to the above 'Calling Code'. This just displays a black texture.. my original issue. Out of desperation, I just tried changing the name in glGetUniformLocation from "textureData" to "textureData_invalid" to see if my error checks would through up something, but in actual fact, it is now displaying the texture as expected. Can anyone fathom a guess as too why this is occurring.. im assuming the random text is just picking up the correct location by c++ witchcraft, but why is the original one not getting picked up correctly and/or not working as expected
      I realize more code is probably needed to see how it all hangs together.. but it seems to come down to this as the issue
    • By QQemka
      Hello. So far i got decently looking 3d scene. I also managed to render a truetype font, on my way to implementing gui (windows, buttons and textboxes). There are several issues i am facing, would love to hear your feedback.
      1) I render text using atlas with VBO containing x/y/u/v of every digit in the atlas (calculated basing on x/y/z/width/height/xoffset/yoffset/xadvance data in binary .fnt format file, screenshot 1). I generated a Comic Sans MS with 32 size and times new roman with size 12 (screenshot 2 and 3). The first issue is the font looks horrible when rescaling. I guess it is because i am using fixed -1 to 1 screen space coords. This is where ortho matrix should be used, right?
      2) Rendering GUI. Situation is similar to above. I guess the widgets should NOT scale when scaling window, am i right? So what am i looking for is saying "this should be always in the middle, 200x200 size no matter the display window xy", and "this should stick to the bottom left corner". Is ortho matrix the cure for all such problems?
      3) The game is 3D but i have to go 2D to render static gui elements over the scene - and i want to do it properly! At the moment i am using matrix 3x3 for 2d transformations and vec3 for all kinds of coordinates. In shaders tho i technically still IS 3D. I have to set all 4 x y z w of the gl_Position while it would be much much more conventient to... just do the maths in 2d space. Can i achieve it somehow?
      4) Text again. I am kind of confused what is the reason of artifacts in Times New Roman font displaying (screenshot 1). I render from left to right, letter after letter. You can clearly see that letters on the right (so the ones rendered after ones on the left are covered by the previous one). I was toying around with blending options but no luck. I do not support kerning at the moment but that's definitely not the cause of error. The display of the small font looks dirty aliased too. I am knd of confused how to interpret the integer data and how should be scaled/adapted to the screen view. Is it just store the data as constant size and again - use ortho matrix?
      Thanks in advance for all your ideas and suggestions!
      https://i.imgur.com/4rd1VC3.png
      https://i.imgur.com/uHrSXfe.png
      https://i.imgur.com/xRTffPn.png
    • By plz717
      Hello, everyone! I hope my problem isn't too 'beginnerish'. I'm doing research on motion synthesis now, trying to implement the Deep Mimic paper (DeepMimic) by BINPENG XUE, in this paper, I need to first retarget character A's motion to another character B to make the reference motion clips for character B, since we don't have character B‘s reference motion. The most important thing is that in the paper, the author copied character A's joint's rotation with respective to joint's local coordinate system (not the parent) to character B. In my personal understanding, the joint's rotation with respective to joint's local coordinate system is something like that in the attached photo, where for the Elbow joint, i need to get the Elbow's rotation in the elbow's local coordinate system (i'm very grateful for you to share your ideas if i have misunderstanding about it 🙂)
      I have searched many materials on the internet about how to extract the local joint's information from FBX, the most relative one i found is the pivot rotation( and geometric transformation, object offset transformation). I'm a beginner in computer graphics, and i'm confused about whether the pivot rotation( or geometric transformation, object offset transformation) is exactly the joint's local rotation i'm seeking? I hope someone that have any ideas can help me, I'd be very grateful for any pointers in the right direction. Thanks in advance! 

    • By nOoNEE
      hello guys , i have some questions  what does glLinkProgram  and  glBindAttribLocation do?  i searched but there wasnt any good resource 
    • By owenjr
      Hi, I'm a Multimedia Engineering student. I am about to finish my dergree and I'm already thinking about what topic to cover in my final college project.
      I'm interested in the procedural animation with c++ and OpenGL of creatures, something like a spider for example. Can someone tell me what are the issues I should investigate to carry it out? I understand that it has some dependence on artificial intelligence but I do not know to what extent. Can someone help me to find information about it? Thank you very much.
       
      Examples: 
      - Procedural multi-legged walking animation
      - Procedural Locomotion of Multi-Legged Characters in Dynamic Environments
    • By Lewa
      So, i'm still on my quest to unterstanding the intricacies of HDR and implementing this into my engine. Currently i'm at the step to implementing tonemapping. I stumbled upon this blogposts:
      http://filmicworlds.com/blog/filmic-tonemapping-operators/
      http://frictionalgames.blogspot.com/2012/09/tech-feature-hdr-lightning.html
      and tried to implement some of those mentioned tonemapping methods into my postprocessing shader.
      The issue is that none of them creates the same results as shown in the blogpost which definitely has to do with the initial range in which the values are stored in the HDR buffer. For simplicity sake i store the values between 0 and 1 in the HDR buffer (ambient light is 0.3, directional light is 0.7)
      This is the tonemapping code:
      vec3 Uncharted2Tonemap(vec3 x) { float A = 0.15; float B = 0.50; float C = 0.10; float D = 0.20; float E = 0.02; float F = 0.30; return ((x*(A*x+C*B)+D*E)/(x*(A*x+B)+D*F))-E/F; } This is without the uncharted tonemapping:
      This is with the uncharted tonemapping:
      Which makes the image a lot darker.
      The shader code looks like this:
      void main() { vec3 color = texture2D(texture_diffuse, vTexcoord).rgb; color = Uncharted2Tonemap(color); //gamma correction (use only if not done in tonemapping code) color = gammaCorrection(color); outputF = vec4(color,1.0f); } Now, from my understanding is that tonemapping should bring the range down from HDR to 0-1.
      But the output of the tonemapping function heavily depends on the initial range of the values in the HDR buffer. (You can't expect to set the sun intensity the first time to 10 and the second time to 1000 and excpect the same result if you feed that into the tonemapper.) So i suppose that this also depends on the exposure which i have to implement?
      To check this i plotted the tonemapping curve:
      You can see that the curve goes only up to around to a value of 0.21 (while being fed a value of 1) and then basically flattens out. (which would explain why the image got darker.)
       
      My guestion is: In what range should the values in the HDR buffer be which then get tonemapped? Do i have to bring them down to a range of 0-1 by multiplying with the exposure?
      For example, if i increase the values of the light by 10 (directional light would be 7 and ambient light 3) then i would need to divide HDR values by 10 in order to get a value range of 0-1 which then could be fed into the tonemapping curve. Is that correct?
    • By nOoNEE
      i am reading this book : link
      in the OpenGL Rendering Pipeline section there is a picture like this: link
      but the question is this i dont really understand why it is necessary to turn pixel data in to fragment and then fragment into pixel could please give me a source or a clear Explanation that why it is necessary ? thank you so mu
       
       
    • By Inbar_xz
      I'm using the OPENGL with eclipse+JOGL.
      My goal is to create movement of the camera and the player.
      I create main class, which create some box in 3D and hold 
      an object of PlayerAxis.
      I create PlayerAxis class which hold the axis of the player.
      If we want to move the camera, then in the main class I call to 
      the func "cameraMove"(from PlayerAxis) and it update the player axis.
      That's work good.
      The problem start if I move the camera on 2 axis, 
      for example if I move with the camera right(that's on the y axis)
      and then down(on the x axis) -
      in some point the move front is not to the front anymore..
      In order to move to the front, I do
      player.playerMoving(0, 0, 1);
      And I learn that in order to keep the front move, 
      I need to convert (0, 0, 1) to the player axis, and then add this.
      I think I dont do the convert right.. 
      I will be glad for help!

      Here is part of my PlayerAxis class:
       
      //player coordinate float x[] = new float[3]; float y[] = new float[3]; float z[] = new float[3]; public PlayerAxis(float move_step, float angle_move) { x[0] = 1; y[1] = 1; z[2] = -1; step = move_step; angle = angle_move; setTransMatrix(); } public void cameraMoving(float angle_step, String axis) { float[] new_x = x; float[] new_y = y; float[] new_z = z; float alfa = angle_step * angle; switch(axis) { case "x": new_z = addVectors(multScalar(z, COS(alfa)), multScalar(y, SIN(alfa))); new_y = subVectors(multScalar(y, COS(alfa)), multScalar(z, SIN(alfa))); break; case "y": new_x = addVectors(multScalar(x, COS(alfa)), multScalar(z, SIN(alfa))); new_z = subVectors(multScalar(z, COS(alfa)), multScalar(x, SIN(alfa))); break; case "z": new_x = addVectors(multScalar(x, COS(alfa)), multScalar(y, SIN(alfa))); new_y = subVectors(multScalar(y, COS(alfa)), multScalar(x, SIN(alfa))); } x = new_x; y = new_y; z = new_z; normalization(); } public void playerMoving(float x_move, float y_move, float z_move) { float[] move = new float[3]; move[0] = x_move; move[1] = y_move; move[2] = z_move; setTransMatrix(); float[] trans_move = transVector(move); position[0] = position[0] + step*trans_move[0]; position[1] = position[1] + step*trans_move[1]; position[2] = position[2] + step*trans_move[2]; } public void setTransMatrix() { for (int i = 0; i < 3; i++) { coordiTrans[0][i] = x[i]; coordiTrans[1][i] = y[i]; coordiTrans[2][i] = z[i]; } } public float[] transVector(float[] v) { return multiplyMatrixInVector(coordiTrans, v); }  
      and in the main class i have this:
       
      public void keyPressed(KeyEvent e) { if (e.getKeyCode()== KeyEvent.VK_ESCAPE) { System.exit(0); //player move } else if (e.getKeyCode()== KeyEvent.VK_W) { //front //moveAmount[2] += -0.1f; player.playerMoving(0, 0, 1); } else if (e.getKeyCode()== KeyEvent.VK_S) { //back //moveAmount[2] += 0.1f; player.playerMoving(0, 0, -1); } else if (e.getKeyCode()== KeyEvent.VK_A) { //left //moveAmount[0] += -0.1f; player.playerMoving(-1, 0, 0); } else if (e.getKeyCode()== KeyEvent.VK_D) { //right //moveAmount[0] += 0.1f; player.playerMoving(1, 0, 0); } else if (e.getKeyCode()== KeyEvent.VK_E) { //moveAmount[0] += 0.1f; player.playerMoving(0, 1, 0); } else if (e.getKeyCode()== KeyEvent.VK_Q) { //moveAmount[0] += 0.1f; player.playerMoving(0, -1, 0); //camera move } else if (e.getKeyCode()== KeyEvent.VK_I) { //up player.cameraMoving(1, "x"); } else if (e.getKeyCode()== KeyEvent.VK_K) { //down player.cameraMoving(-1, "x"); } else if (e.getKeyCode()== KeyEvent.VK_L) { //right player.cameraMoving(-1, "y"); } else if (e.getKeyCode()== KeyEvent.VK_J) { //left player.cameraMoving(1, "y"); } else if (e.getKeyCode()== KeyEvent.VK_O) { //right round player.cameraMoving(-1, "z"); } else if (e.getKeyCode()== KeyEvent.VK_U) { //left round player.cameraMoving(1, "z"); } }  
      finallt found it.... i confused with the transformation matrix row and col. thanks anyway!
    • By Lewa
      So, i'm currently trying to implement an SSAO shader from THIS tutorial and i'm running into a few issues here.
      Now, this SSAO method requires view space positions and normals. I'm storing the normals in my deferred renderer in world-space so i had to do a conversion and reconstruct the position from the depth buffer.
      And something there goes horribly wrong (which has probably to do with worldspace to viewspace transformations).
      (here is the full shader source code if someone wants to take a look at it)
      Now, i suspect that the normals are the culprit.
      vec3 normal = ((uNormalViewMatrix*vec4(normalize(texture2D(sNormals, vTexcoord).rgb),1.0)).xyz); "sNormals" is a 2D texture which stores the normals in world space in a RGB FP16 buffer.
      Now i can't use the camera viewspace matrix to transform the normals into viewspace as the cameras position isn't set at (0,0,0), thus skewing the result.
      So what i did is to create a new viewmatrix specifically for this normal without the position at vec3(0,0,0);
      //"camera" is the camera which was used for rendering the normal buffer renderer.setUniform4m(ressources->shaderSSAO->getUniform("uNormalViewMatrix"), glmExt::createViewMatrix(glm::vec3(0,0,0),camera.getForward(),camera.getUp())//parameters are (position,forwardVector,upVector) ); Though i have the feeling this is the wrong approach. Is this right or is there a better/correct way of transforming a world space normal into viewspace?
    • By HawkDeath
      Hi,
      I'm trying mix two textures using own shader system, but I have a problem (I think) with uniforms.
      Code: https://github.com/HawkDeath/shader/tree/test
      To debug I use RenderDocs, but I did not receive good results. In the first attachment is my result, in the second attachment is what should be.
      PS. I base on this tutorial https://learnopengl.com/Getting-started/Textures.


  • Advertisement
  • Popular Now

  • Forum Statistics

    • Total Topics
      631398
    • Total Posts
      2999838
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

Participate in the game development conversation and more when you create an account on GameDev.net!

Sign me up!