Sign in to follow this  

OpenGL Drawing image out of multi-channel interleaved data

Recommended Posts


I'm hoping someone could give me a clue for implementing what I'm trying to do.

I'm reading a file containing a very large 3D array containing multichannel interleaved data (multiple GB).

Out of this big array I'm extracting only 3 arbitrary channels out of X for each frame in order to display an RGB representation.

So at the moment I have 3 arrays containing the values of each pixels in a raw for each color:

UINT16* pRedBand = new UINT16[width * height];
UINT16* pGreenBand = new UINT16[width * height];
UINT16* pBlueBand = new UINT16[width * height];

This is 2 byte unsingned data so I have been using GLushort type to try to create a bitmap buffer.

I tried to take the approach of creating a texture but every time I call glTexImage2D I get a GL_INVALID_VALUE error code most certainly due to the fact that the texture dimensions are not power of 2 for with and height.

But if I create a texture of out of power of 2 dimensions then I'll have an oversize texture and will have a wrong aspect ratio when trying to draw the texture am I right?

Have I taken a wrong approach?

How can I create an image of arbitrary size and draw it using OpenGL.

Thanks in advance!

Share this post

Link to post
Share on other sites
With what arguments are you calling glTexImage2d? Are you absolutely certain that that call is giving you the error? (put glGetError before/after the call).


But if I create a texture of out of power of 2 dimensions then I'll have an oversize texture and will have a wrong aspect ratio when trying to draw the texture am I right?

If you do have to use PoT textures (which is kind of surprising, that hasn't been a requirement on modern hardware for a while), then there's no requirement that you draw the whole texture. When you draw you get to choose what parts of the texture you want to draw from, so the aspect ratio when you draw is entirely up to you and shouldn't be a problem. The only potential downside of PoT textures vs non-PoT is a little bit of wasted vidmem. The end result should look exactly the same.

Share this post

Link to post
Share on other sites
Hi karwosts!

Thanks for answering! The code is not rocket science and I can share it with you. The building of the image buffer is unfinished.

UINT nSamples = GetSamples();
UINT nLines = GetLines();
UINT16* pRedBand = GetRedBandBuffer();
UINT16* pGreenBand = GetGreenBandBuffer();
UINT16* pBlueBand = GetBlueBandBuffer();
GLushort* pImageBuf = new GLushort[nSamples * nLines * 3];

ZeroMemory(pImageBuf, nSamples * nLines * 3 * sizeof(GLushort));

UINT nOffset = 0;
UINT nPointer = 0;

for(UINT nHeight = 0; nHeight < nLines; nHeight++)
for(UINT nWidth = 0; nWidth < nSamples; nWidth++)
nPointer = nHeight * nWidth;
nOffset = nPointer * 3;

// Red
pImageBuf[nOffset] = pRedBand[nPointer];

// Green
pImageBuf[nOffset + 1] = pGreenBand[nPointer];

// Blue
pImageBuf[nOffset + 2] = pBlueBand[nPointer];

glGenTextures(1, &m_nTexture1);
glBindTexture(GL_TEXTURE_2D, m_nTexture1);



glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, nSamples, nLines, 0, GL_RGB, GL_UNSIGNED_SHORT, pImageBuf);

Maybe you are better able to tell me what I am doing wrong. I went through the code and tested line by line, the gl error comes only after calling glTexImage2D.

Any thoughts?


Share this post

Link to post
Share on other sites
Firstly there seems to be a mistake in your loop. Shouldn't nPointer be
nPointer = nHeight * nSamples + nWidth

EDIT: Also I think that OpenGL pads rows so that they are even. So if nSamples * 3 is an odd number, glTexImage2D might be expecting rows of nSamples * 3 + 1

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  

  • Partner Spotlight

  • Forum Statistics

    • Total Topics
    • Total Posts
  • Similar Content

    • By xhcao
      Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness. 
    • By cebugdev
      hi guys, 
      are there any books, link online or any other resources that discusses on how to build special effects such as magic, lightning, etc. in OpenGL? i mean, yeah most of them are using particles but im looking for resources specifically on how to manipulate the particles to look like an effect that can be use for games,. i did fire particle before, and I want to learn how to do the other 'magic' as well.
      Like are there one book or link(cant find in google) that atleast featured how to make different particle effects in OpenGL (or DirectX)? If there is no one stop shop for it, maybe ill just look for some tips on how to make a particle engine that is flexible enough to enable me to design different effects/magic 
      let me know if you guys have recommendations.
      Thank you in advance!
    • By dud3
      How do we rotate the camera around x axis 360 degrees, without having the strange effect as in my video below? 
      Mine behaves exactly the same way spherical coordinates would, I'm using euler angles.
      Tried googling, but couldn't find a proper answer, guessing I don't know what exactly to google for, googled 'rotate 360 around x axis', got no proper answers.
      The video shows the difference between blender and my rotation:
    • By Defend
      I've had a Google around for this but haven't yet found some solid advice. There is a lot of "it depends", but I'm not sure on what.
      My question is what's a good rule of thumb to follow when it comes to creating/using VBOs & VAOs? As in, when should I use multiple or when should I not? My understanding so far is that if I need a new VBO, then I need a new VAO. So when it comes to rendering multiple objects I can either:
      * make lots of VAO/VBO pairs and flip through them to render different objects, or
      * make one big VBO and jump around its memory to render different objects. 
      I also understand that if I need to render objects with different vertex attributes, then a new VAO is necessary in this case.
      If that "it depends" really is quite variable, what's best for a beginner with OpenGL, assuming that better approaches can be learnt later with better understanding?
    • By test opty
      Hello all,
      On my Windows 7 x64 machine I wrote the code below on VS 2017 and ran it.
      #include <glad/glad.h>  #include <GLFW/glfw3.h> #include <std_lib_facilities_4.h> using namespace std; void framebuffer_size_callback(GLFWwindow* window , int width, int height) {     glViewport(0, 0, width, height); } //****************************** void processInput(GLFWwindow* window) {     if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)         glfwSetWindowShouldClose(window, true); } //********************************* int main() {     glfwInit();     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);     //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);     GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", nullptr, nullptr);     if (window == nullptr)     {         cout << "Failed to create GLFW window" << endl;         glfwTerminate();         return -1;     }     glfwMakeContextCurrent(window);     if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))     {         cout << "Failed to initialize GLAD" << endl;         return -1;     }     glViewport(0, 0, 600, 480);     glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);     glClearColor(0.2f, 0.3f, 0.3f, 1.0f);     glClear(GL_COLOR_BUFFER_BIT);     while (!glfwWindowShouldClose(window))     {         processInput(window);         glfwSwapBuffers(window);         glfwPollEvents();     }     glfwTerminate();     return 0; }  
      The result should be a fixed dark green-blueish color as the end of here. But the color of my window turns from black to green-blueish repeatedly in high speed! I thought it might be a problem with my Graphics card driver but I've updated it and it's: NVIDIA GeForce GTX 750 Ti.
      What is the problem and how to solve it please?
  • Popular Now