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openglbitmapglutfreeglut

OpenGL image not mapping to coordinates

When I am trying to display images on a square, they are not mapping properly to corners. These are the original images and the outputs -

Original Image

enter image description here

enter image description here

enter image description here

I had downloaded original images from the net, and then converted them to bmp using online converter to use them in the code.

here is the code -

#include <stdio.h> 
#include <GL/glut.h>
GLuint LoadBMP(const char *fileName)
{
    FILE *file;
    unsigned char header[54],*data;
    unsigned int dataPos,size,width, height;
    file = fopen(fileName, "rb");
    fread(header, 1, 54, file);
    dataPos = *(int*)&(header[0x0A]);
    size = *(int*)&(header[0x22]);
    width = *(int*)&(header[0x12]);
    height = *(int*)&(header[0x16]);
    if (size == 0) size = width * height * 3;
    if (dataPos == 0) dataPos = 54;
    data = new unsigned char[size];
    fread(data, 1, size, file);
    fclose(file);
    GLuint texture;
    glGenTextures(1, &texture); 
    glBindTexture(GL_TEXTURE_2D, texture);  
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);  
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, data); 
    return texture;
}
GLint texture;

void display(void) 
{ 
 glClear( GL_COLOR_BUFFER_BIT); 
 // glColor3f(0.0, 1.0, 0.0); 
 glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, texture);
 glBegin(GL_POLYGON); 
  glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.5, -0.5, 0.0); 
  glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.5, 0.5, 0.0); 
  glTexCoord2f(1.0f, 1.0f); glVertex3f(0.5, 0.5, 0.0); 
  glTexCoord2f(1.0f, 0.0f); glVertex3f(0.5, -0.5, 0.0); 
 glEnd(); 
 glDisable(GL_TEXTURE_2D);

 glFlush(); 
}

int main(int argc, char **argv) 
{ 
 printf("hello world\n"); 
 glutInit(&argc, argv); 
 glutInitDisplayMode ( GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);

 glutInitWindowPosition(100,100); 
 glutInitWindowSize(500,500); 
 glViewport(0, 0, 500, 500);
 glutCreateWindow ("square");

 glClearColor(0.0, 0.0, 0.0, 0.0);         // black background 
 glMatrixMode(GL_PROJECTION);              // setup viewing projection 
 glLoadIdentity();                           // start with identity matrix 

 glutDisplayFunc(display); 
 texture = LoadBMP("wall.bmp");
 glutMainLoop();

 return 0; 
}
Solution

  • Your code uses a static header size, thus it looks like it could be a problem due to the differences in the BMP header changes due to OS changes by Microsoft.

    If you are using Linux, try using the file command, to find out which type of BMP you are using:

    BMP Headers

    Your code looks like it works well for Window 3.x format, and you should try converting into that format and check again. You can use ffmpeg for that purpose:

    ffmpeg