Sign in to follow this  

OpenGL Capture the output of OpenGl program

Recommended Posts

kmyadam    122
Hi, I am working with OpenGL on Linux. i want the output of the program to be saved as an image file. How is this task done in OpenGL. Should i write a program to redirect the output to an image file or should i use an application software. Please anyone help me in this regard.

Share this post

Link to post
Share on other sites
w00f    176
You can read the current screen (as an array of pixel values) with glReadPixels, and then once you have an array of pixel values you just need to hand it to *insert image saving library*. For example, with SDL, just use the array to create a surface and use SDL_SaveBMP.

Share this post

Link to post
Share on other sites
kmyadam    122
yaa, i am aware of glReadPixel but i dont know how to save it using SDL, i never used it. can you tell me where can i find some related info

Share this post

Link to post
Share on other sites
w00f    176
Webpage is, check out I think SDL_CreateSurfaceFromRGB, and SDL_SaveBMP which is pretty simple. I can paste my screenshot code when I get home, if you still need it then.

Share this post

Link to post
Share on other sites
kmyadam    122
I will be greatful to you, if you can post me the sample code of the screen shot code.

Also is SDL a library? should i install in it in my system ? or it comes with the OpenGL package on Linux itself???

Share this post

Link to post
Share on other sites
w00f    176
It's a cross-platform library with a bunch of useful utility stuff, like creating a window, loading images, playing sounds, detecting input, etc, and you can make OpenGL run on top of it (unfortunately, I don't have any good tutorial links handy). I use it as the base code for all of my personal projects :D. You need to download it seperately, if you want to use it.

Alternatively, anything like DevIL, lib[type of image format], or just a set of BMP functions (win32 has them, although I forget what they are called, and XWin probably does too), would work. The BMP format is pretty simple, so you might even be able to just code a quick function to export the pictures. Targa is another easy format to work with.

It's worth noting that if you want to export as a format other than BMP, you'll need to use DevIL (or an equivalent image loading/saving library) or write your own exporter. I'm a big fan of saving as BMP and converting to PNG, so I don't need to touch PNG code.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Similar Content

    • By Arulbabu Donbosco
      There are studios selling applications which is just copying any 3Dgraphic content and regenerating into another new window. especially for CAVE Virtual reality experience. so that the user opens REvite or CAD or any other 3D applications and opens a model. then when the user selects the rendered window the VR application copies the 3D model information from the OpenGL window. 
      I got the clue that the VR application replaces the windows opengl32.dll file. how this is possible ... how can we copy the 3d content from the current OpenGL window.
      anyone, please help me .. how to go further... to create an application like VR CAVE. 
    • By cebugdev
      hi all,

      i am trying to build an OpenGL 2D GUI system, (yeah yeah, i know i should not be re inventing the wheel, but this is for educational and some other purpose only),
      i have built GUI system before using 2D systems such as that of HTML/JS canvas, but in 2D system, i can directly match a mouse coordinates to the actual graphic coordinates with additional computation for screen size/ratio/scale ofcourse.
      now i want to port it to OpenGL, i know that to render a 2D object in OpenGL we specify coordiantes in Clip space or use the orthographic projection, now heres what i need help about.
      1. what is the right way of rendering the GUI? is it thru drawing in clip space or switching to ortho projection?
      2. from screen coordinates (top left is 0,0 nd bottom right is width height), how can i map the mouse coordinates to OpenGL 2D so that mouse events such as button click works? In consideration ofcourse to the current screen/size dimension.
      3. when let say if the screen size/dimension is different, how to handle this? in my previous javascript 2D engine using canvas, i just have my working coordinates and then just perform the bitblk or copying my working canvas to screen canvas and scale the mouse coordinates from there, in OpenGL how to work on a multiple screen sizes (more like an OpenGL ES question).
      lastly, if you guys know any books, resources, links or tutorials that handle or discuss this, i found one with marekknows opengl game engine website but its not free,
      Just let me know. Did not have any luck finding resource in google for writing our own OpenGL GUI framework.
      IF there are no any available online, just let me know, what things do i need to look into for OpenGL and i will study them one by one to make it work.
      thank you, and looking forward to positive replies.
    • By fllwr0491
      I have a few beginner questions about tesselation that I really have no clue.
      The opengl wiki doesn't seem to talk anything about the details.
      What is the relationship between TCS layout out and TES layout in?
      How does the tesselator know how control points are organized?
          e.g. If TES input requests triangles, but TCS can output N vertices.
             What happens in this case?
      In this article,
      the isoline example TCS out=4, but TES in=isoline.
      And gl_TessCoord is only a single one.
      So which ones are the control points?
      How are tesselator building primitives?
    • By Orella
      I've been developing a 2D Engine using SFML + ImGui.
      Here you can see an image
      The editor is rendered using ImGui and the scene window is a sf::RenderTexture where I draw the GameObjects and then is converted to ImGui::Image to render it in the editor.
      Now I need to create a 3D Engine during this year in my Bachelor Degree but using SDL2 + ImGui and I want to recreate what I did with the 2D Engine. 
      I've managed to render the editor like I did in the 2D Engine using this example that comes with ImGui. 
      3D Editor preview
      But I don't know how to create an equivalent of sf::RenderTexture in SDL2, so I can draw the 3D scene there and convert it to ImGui::Image to show it in the editor.
      If you can provide code will be better. And if you want me to provide any specific code tell me.
    • By Picpenguin
      I'm new to learning OpenGL and still learning C. I'm using SDL2, glew, OpenGL 3.3, linmath and stb_image.
      I started following through and got through it until I had to load models. The problem is, it uses Assimp for loading models. Assimp is C++ and uses things I don't want in my program (boost for example) and C support doesn't seem that good.
      Things like glVertexAttribPointer and shaders are still confusing to me, but I have to start somewhere right?
      I can't seem to find any good loading/rendering tutorials or source code that is simple to use and easy to understand.
      I have tried this for over a week by myself, searching for solutions but so far no luck. With tinyobjloader-c and project that uses it, FantasyGolfSimulator, I was able to actually load the model with plain color (always the same color no matter what I do) on screen and move it around, but cannot figure out how to use textures or use its multiple textures with it.
      I don't ask much: I just want to load models with textures in them, maybe have lights affect them (directional spotlight etc). Also, some models have multiple parts and multiple textures in them, how can I handle those?
      Are there solutions anywhere?
      Thank you for your time. Sorry if this is a bit confusing, English isn't my native language
  • Popular Now