Sign in to follow this  

OpenGL Problem loading a particular .png file

Recommended Posts

Monkey_Missile    104

I've been using SDL with openGL to create a project and for some reason using IMG_Load followed by SDL_DisplayFormatAlpha causes a crash only when I use the attached file. I'm doing this in Code::Blocks so I'm not sure if the file is just too big or what. Any guesses as to what might be doing this and how to resolve it?



Share this post

Link to post
Share on other sites
L. Spiro    25622

Never used SDL but that sounds like a loading bug, possibly a buffer overflow that doesn’t get caught until later.

A stack trace and any reported errors would be helpful.


Things to try in the meantime:

#1: Check the format of the .PNG (bits per pixel) and save it as 32 bits per pixel if it is not already.

#2: Modify the image to see which part of it is related to the crash.

#3: Save it as a .BMP or .TGA and see if it still happens.


These of course are only running away from the problem but would at least give you some idea as to where it could be.



L. Spiro

Share this post

Link to post
Share on other sites
mhagain    13430

My thought is - because it's a 1024x800 image - the OP may have an older GPU that doesn't support non-power-of-two textures.  Now, OpenGL shouldn't cause a crash on an attempt to load that (error behaviour being well-specified) but that assumes a conformant (and non-buggy) driver, and we all know how many of those exist (hint: none).


Of course, we do need more info from the OP to diagnose this properly.

Share this post

Link to post
Share on other sites
Monkey_Missile    104

I'm using an NVIDIA GeForce GTX560 Ti. I've changed the image to a 1024x1024 and still no dice plus other non-power-of-two images still work. Changing it to a .bmp works but only if 32 bit. 16 and 24 bit still crash. Also .png files from what I gather can only be 8 bit but that can't be it since the other smaller 48x48 texture which is a .png works fine.


I was hoping to avoid .bmp files due to their size so I'll still try fixing this before doing that. If this is a problem in the beginning where openGL is being initialized then I'm not sure where to look. The code from the init is as follows:


    //Initialize SDL
    if(SDL_Init(SDL_INIT_EVERYTHING) < 0){
        return false;

    //Set OpenGL memory usage
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 16);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

    //Set window caption
    SDL_WM_SetCaption("Test", NULL);

    //Size of the window
        return false;

    //Specify the clear color and what portion of the screen will display

    //Shader model

    //2D rendering

    //Depth testing only used with 3D rendering


Share this post

Link to post
Share on other sites

How are you loading the PNG? Also, are you making sure the PNG is being converted to 32-bit RGBA? If you're using libpng directly and you're using the "high level" loading functions, you can pass some flags to get it to convert to that format for you.


What format is this PNG, by the way?


PS: PNG supports a ton of formats (between paletted, grayscale and RGB along with alpha or not alpha and 8-bit or 16-bit components - or even 4-bit in one case). Be careful. Luckily you can still turn it into 32-bit RGBA only so don't bother much about that if you tell libpng to convert it on its own.

Edited by Sik_the_hedgehog

Share this post

Link to post
Share on other sites
Monkey_Missile    104

Ugh sorry about the delay there. Here's the image load function, which part would allow me to convert the format?


GLuint mainApp::OnLoad(const std::string &fileName){
    SDL_Surface *image = IMG_Load(fileName.c_str());

    unsigned object(0);

    glGenTextures(1, &object);
    glBindTexture(GL_TEXTURE_2D, object);


    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->w, image->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);

    return object;

Share this post

Link to post
Share on other sites
Sponji    2503

Your image doesn't have alpha and you're using it as it would have it.


GLenum format;

if(image->format->BytesPerPixel == 3) format = GL_RGB;
else if(image->format->BytesPerPixel == 4) format = GL_RGBA;

glTexImage2D(GL_TEXTURE_2D, 0, format, image->w, image->h, 0, format, GL_UNSIGNED_BYTE, image->pixels); 


The SDL_Surface's format could be something else too, like BGR, but this is just an example. Google for SDL_Surface's manual and glTexImage2D and you should find some good information about the formats.

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 povilaslt2
      Hello. I'm Programmer who is in search of 2D game project who preferably uses OpenGL and C++. You can see my projects in GitHub. Project genre doesn't matter (except MMO's :D).
    • By ZeldaFan555
      Hello, My name is Matt. I am a programmer. I mostly use Java, but can use C++ and various other languages. I'm looking for someone to partner up with for random projects, preferably using OpenGL, though I'd be open to just about anything. If you're interested you can contact me on Skype or on here, thank you!
      Skype: Mangodoor408
    • By tyhender
      Hello, my name is Mark. I'm hobby programmer. 
      So recently,I thought that it's good idea to find people to create a full 3D engine. I'm looking for people experienced in scripting 3D shaders and implementing physics into engine(game)(we are going to use the React physics engine). 
      And,ye,no money =D I'm just looking for hobbyists that will be proud of their work. If engine(or game) will have financial succes,well,then maybe =D
      Sorry for late replies.
      I mostly give more information when people PM me,but this post is REALLY short,even for me =D
      So here's few more points:
      Engine will use openGL and SDL for graphics. It will use React3D physics library for physics simulation. Engine(most probably,atleast for the first part) won't have graphical fron-end,it will be a framework . I think final engine should be enough to set up an FPS in a couple of minutes. A bit about my self:
      I've been programming for 7 years total. I learned very slowly it as "secondary interesting thing" for like 3 years, but then began to script more seriously.  My primary language is C++,which we are going to use for the engine. Yes,I did 3D graphics with physics simulation before. No, my portfolio isn't very impressive. I'm working on that No,I wasn't employed officially. If anybody need to know more PM me. 
    • By Zaphyk
      I am developing my engine using the OpenGL 3.3 compatibility profile. It runs as expected on my NVIDIA card and on my Intel Card however when I tried it on an AMD setup it ran 3 times worse than on the other setups. Could this be a AMD driver thing or is this probably a problem with my OGL code? Could a different code standard create such bad performance?
    • By Kjell Andersson
      I'm trying to get some legacy OpenGL code to run with a shader pipeline,
      The legacy code uses glVertexPointer(), glColorPointer(), glNormalPointer() and glTexCoordPointer() to supply the vertex information.
      I know that it should be using setVertexAttribPointer() etc to clearly define the layout but that is not an option right now since the legacy code can't be modified to that extent.
      I've got a version 330 vertex shader to somewhat work:
      #version 330 uniform mat4 osg_ModelViewProjectionMatrix; uniform mat4 osg_ModelViewMatrix; layout(location = 0) in vec4 Vertex; layout(location = 2) in vec4 Normal; // Velocity layout(location = 3) in vec3 TexCoord; // TODO: is this the right layout location? out VertexData { vec4 color; vec3 velocity; float size; } VertexOut; void main(void) { vec4 p0 = Vertex; vec4 p1 = Vertex + vec4(Normal.x, Normal.y, Normal.z, 0.0f); vec3 velocity = (osg_ModelViewProjectionMatrix * p1 - osg_ModelViewProjectionMatrix * p0).xyz; VertexOut.velocity = velocity; VertexOut.size = TexCoord.y; gl_Position = osg_ModelViewMatrix * Vertex; } What works is the Vertex and Normal information that the legacy C++ OpenGL code seem to provide in layout location 0 and 2. This is fine.
      What I'm not getting to work is the TexCoord information that is supplied by a glTexCoordPointer() call in C++.
      What layout location is the old standard pipeline using for glTexCoordPointer()? Or is this undefined?
      Side note: I'm trying to get an OpenSceneGraph 3.4.0 particle system to use custom vertex, geometry and fragment shaders for rendering the particles.
  • Popular Now