• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
nyl2000

OpenGL
Creating texture from BMP file

2 posts in this topic

I am currently trying to draw a plane texture in openGL from a loaded BMP file. Only I don't know the exact codes to do this. I understand that getBMPData(), glBindTexture(), and glTexImage() are some of the functions I need, but I could use an example to understand how to use them.

0

Share this post


Link to post
Share on other sites
// To create our window
#include <GL/glut.h>

#ifndef GL_BGRA
#define GL_BGRA 0x80E1
#endif

// For BITMAPFILEHEADER and BITMAPINFOHEADER
#include <windows.h>

#include <stdio.h>

GLuint test_texture_id;

void display(){
    glClear(GL_COLOR_BUFFER_BIT);

    // One vertex is (2 + 2)*4 bytes (2 GLfloats for position, 2 GLfloats for texture coordinates, 4 bytes per GLfloat)
    const int SIZE_OF_VERTEX = (2 + 2)*sizeof(GLfloat);

    GLfloat data[] = {// 2 texture coordinates followed by 2 vertex coordinates in counterclockwise order
        0, 0, -1, -1,// Bottomleft
        1, 0, +1, -1,// Bottomright
        1, 1, +1, +1,// Topright
        0, 1, -1, +1,// Topleft
    };

    // Use this texture
    glBindTexture(GL_TEXTURE_2D, test_texture_id);



    // Tell OpenGL where our vertex data begins and how big each vertex is
    glTexCoordPointer(2, GL_FLOAT, SIZE_OF_VERTEX, data+0);// Texture data begins at index 0
    glVertexPointer  (2, GL_FLOAT, SIZE_OF_VERTEX, data+2);// Vertex  data begins at index 2
    // Draw data
    glDrawArrays(GL_QUADS, 0, 4);

    // We can also draw like this instead (slower but probably more familiar)
/*
    glBegin(GL_QUADS);
    int i;
    for (i=0; i<16; i+=4){
        glTexCoord2f(data[i+0], data[i+1]);
        glVertex2f(data[i+2], data[i+3]);
    }
    glEnd();
*/
    glutSwapBuffers();
}

void reshape(int w, int h){
    glViewport(0, 0, w, h);
}

int main(int argc, char *argv[]){
    glutInit(&argc, argv);
    glutCreateWindow("");

    glutDisplayFunc(display);
    glutReshapeFunc(reshape);

    // Make us able to draw with single function calls (faster)
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    // Make OpenGL draw texture on our triangles/quads/etc
    glEnable(GL_TEXTURE_2D);

    // Enable alpha so we can see through transparent images
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    // Generate a texture id for our texture so we can find it again later
    glGenTextures(1, &test_texture_id);
    // Use this texture id
    glBindTexture(GL_TEXTURE_2D, test_texture_id);
    // Associate this texture id with some texture-specific data
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

    /// THIS BITMAP _MUST_ BE 32 BIT BMP!!! (e.g. gimp can export these)

    FILE *fp = fopen("test.bmp", "rb");

    // Load bitmap header
    BITMAPINFOHEADER bmih;
    BITMAPFILEHEADER bmfh;
    fread(&bmfh, 1, sizeof(bmfh), fp);
    fread(&bmih, 1, sizeof(bmih), fp);
    fseek(fp, bmfh.bfOffBits, SEEK_SET);
    // Width of image should be 2^n (2, 4, 8, 16, 32, 64, ...)
    int w = bmih.biWidth;
    int h = bmih.biHeight;
    // Number of bytes (RGBA = 4*1 byte, one byte per color)
    int n = w*h*4;
    void *data = malloc(n);
    fread(data, 1, n, fp);
    // Data loaded from disc to RAM, no need to keep this file open
    fclose(fp);

    // Upload data to GPU (we use GL_BGRA format because bmp colors are messed up)
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_BGRA, GL_UNSIGNED_BYTE, data);

    // Data is in GPU memory, we can delete it from RAM now
    free(data);

    glutMainLoop();

    return 0;
}

I don't recommend this way of loading images or even BMP images, but for testing it is good enough I guess.

I usually use PNG and some library to load it, but the choice mostly depends on what constraints you have.

 

Note that this is very old OpenGL (which is easier to learn imho but slower than new OpenGL and less versatile).

This is newer OpenGL: https://github.com/progschj/OpenGL-Examples

 

For simplicity I used 32-bit bmps because they are easier to load since they don't have weird padding bytes every row of pixels (the alpha channel is nice, too).

 

If you don't have glut and are using Code::Blocks you can get something better here: http://www.transmissionzero.co.uk/software/freeglut-devel/

Just copy the all the include files into your MinGW include folder and the libfreeglut.a into the MinGW lib folder, add -lfreeglut under linkers somewhere and you are good to go (there are other similar ways to do this).

0

Share this post


Link to post
Share on other sites

freeimage is a great library, it uses libpng as well as the other libs for opening image files.  It however makes it much easier to do so.  glfw has a tga loading function.

 

If you really want to learn to load a bmp by hand ( it's a good learning experience ) then you need to find the right information.  Every image has a file header, its the first part of the file's structure that hold the information that you need to know to read and file.  Such as width and height, bits per pixel, things like this.  Once you have that its pretty easy

 

You just read the header into a struct, then your data should be next in the file, from the information in the header you should be able to figure out the total number of bytes in the data section.  Read this in as an array of chars ( or bytes ).  Then when you create your buffer do the following function call to send that data to openGL.

 

//mWidth is the image width from the image header

//mHeight is the image height from the image header

// mpBytes is a pointer to the char array, its size should be (mWidth * mHeight * (bitsPerPixel / 8))  ( this is in bytes ).

 

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, mWidth, mHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, mpBytes );

 

// You may need to change the GL_BGRA to whatever format your image is in.  In my case its R G B and A channels but in BGRA order.

 

There are other ways to send your image data to openGL such as mapping the buffer, but this way is easier.

 

If you want to see an example of bmp loading look at this tutorial

http://www.opengl-tutorial.org

Edited by EddieV223
0

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  
Followers 0

  • Similar Content

    • By Toastmastern
      So it's been a while since I took a break from my whole creating a planet in DX11. Last time around I got stuck on fixing a nice LOD.
      A week back or so I got help to find this:
      https://github.com/sp4cerat/Planet-LOD
      In general this is what I'm trying to recreate in DX11, he that made that planet LOD uses OpenGL but that is a minor issue and something I can solve. But I have a question regarding the code
      He gets the position using this row
      vec4d pos = b.var.vec4d["position"]; Which is then used further down when he sends the variable "center" into the drawing function:
      if (pos.len() < 1) pos.norm(); world::draw(vec3d(pos.x, pos.y, pos.z));  
      Inside the draw function this happens:
      draw_recursive(p3[0], p3[1], p3[2], center); Basically the 3 vertices of the triangle and the center of details that he sent as a parameter earlier: vec3d(pos.x, pos.y, pos.z)
      Now onto my real question, he does vec3d edge_center[3] = { (p1 + p2) / 2, (p2 + p3) / 2, (p3 + p1) / 2 }; to get the edge center of each edge, nothing weird there.
      But this is used later on with:
      vec3d d = center + edge_center[i]; edge_test[i] = d.len() > ratio_size; edge_test is then used to evaluate if there should be a triangle drawn or if it should be split up into 3 new triangles instead. Why is it working for him? shouldn't it be like center - edge_center or something like that? Why adding them togheter? I asume here that the center is the center of details for the LOD. the position of the camera if stood on the ground of the planet and not up int he air like it is now.

      Full code can be seen here:
      https://github.com/sp4cerat/Planet-LOD/blob/master/src.simple/Main.cpp
      If anyone would like to take a look and try to help me understand this code I would love this person. I'm running out of ideas on how to solve this in my own head, most likely twisted it one time to many up in my head
      Thanks in advance
      Toastmastern
       
       
    • By fllwr0491
      I googled around but are unable to find source code or details of implementation.
      What keywords should I search for this topic?
      Things I would like to know:
      A. How to ensure that partially covered pixels are rasterized?
         Apparently by expanding each triangle by 1 pixel or so, rasterization problem is almost solved.
         But it will result in an unindexable triangle list without tons of overlaps. Will it incur a large performance penalty?
      B. A-buffer like bitmask needs a read-modiry-write operation.
         How to ensure proper synchronizations in GLSL?
         GLSL seems to only allow int32 atomics on image.
      C. Is there some simple ways to estimate coverage on-the-fly?
         In case I am to draw 2D shapes onto an exisitng target:
         1. A multi-pass whatever-buffer seems overkill.
         2. Multisampling could cost a lot memory though all I need is better coverage.
            Besides, I have to blit twice, if draw target is not multisampled.
       
    • By mapra99
      Hello

      I am working on a recent project and I have been learning how to code in C# using OpenGL libraries for some graphics. I have achieved some quite interesting things using TAO Framework writing in Console Applications, creating a GLUT Window. But my problem now is that I need to incorporate the Graphics in a Windows Form so I can relate the objects that I render with some .NET Controls.

      To deal with this problem, I have seen in some forums that it's better to use OpenTK instead of TAO Framework, so I can use the glControl that OpenTK libraries offer. However, I haven't found complete articles, tutorials or source codes that help using the glControl or that may insert me into de OpenTK functions. Would somebody please share in this forum some links or files where I can find good documentation about this topic? Or may I use another library different of OpenTK?

      Thanks!
    • By Solid_Spy
      Hello, I have been working on SH Irradiance map rendering, and I have been using a GLSL pixel shader to render SH irradiance to 2D irradiance maps for my static objects. I already have it working with 9 3D textures so far for the first 9 SH functions.
      In my GLSL shader, I have to send in 9 SH Coefficient 3D Texures that use RGBA8 as a pixel format. RGB being used for the coefficients for red, green, and blue, and the A for checking if the voxel is in use (for the 3D texture solidification shader to prevent bleeding).
      My problem is, I want to knock this number of textures down to something like 4 or 5. Getting even lower would be a godsend. This is because I eventually plan on adding more SH Coefficient 3D Textures for other parts of the game map (such as inside rooms, as opposed to the outside), to circumvent irradiance probe bleeding between rooms separated by walls. I don't want to reach the 32 texture limit too soon. Also, I figure that it would be a LOT faster.
      Is there a way I could, say, store 2 sets of SH Coefficients for 2 SH functions inside a texture with RGBA16 pixels? If so, how would I extract them from inside GLSL? Let me know if you have any suggestions ^^.
    • By KarimIO
      EDIT: I thought this was restricted to Attribute-Created GL contexts, but it isn't, so I rewrote the post.
      Hey guys, whenever I call SwapBuffers(hDC), I get a crash, and I get a "Too many posts were made to a semaphore." from Windows as I call SwapBuffers. What could be the cause of this?
      Update: No crash occurs if I don't draw, just clear and swap.
      static PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 24Bit Z-Buffer (Depth Buffer) 0, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; if (!(hDC = GetDC(windowHandle))) return false; unsigned int PixelFormat; if (!(PixelFormat = ChoosePixelFormat(hDC, &pfd))) return false; if (!SetPixelFormat(hDC, PixelFormat, &pfd)) return false; hRC = wglCreateContext(hDC); if (!hRC) { std::cout << "wglCreateContext Failed!\n"; return false; } if (wglMakeCurrent(hDC, hRC) == NULL) { std::cout << "Make Context Current Second Failed!\n"; return false; } ... // OGL Buffer Initialization glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); glBindVertexArray(vao); glUseProgram(myprogram); glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, (void *)indexStart); SwapBuffers(GetDC(window_handle));  
  • Popular Now