Created from BMP texture has excess pixels in OpenGL 2.1-CodePudding

I am using OpenGL 2.1 in my academic work to create a 3D scene. I have a 24-bit BMP file, a texture for a cube side, that is loaded manually into the memory.

Straight to the problem: displayed texture has some excess pixels at the lower left corner. BMP file, of course, doesn't have these pixels, it has a full black border. Here's the result:

Seems like the data loaded from file is OK - pixels in a row after excess once are the same as in file, checked with another varicolored BMP. Here's the function I use to create texture from BMP:

GLuint CreateTextureFromBMP (const char path [])
{
    unsigned char header [54];
    unsigned int  data_position, width, height, image_size;
    unsigned char * data;

    FILE * file = fopen (path, "rb");
    fread (header, sizeof (char), 54, file);

    data_position = *(int *)&(header [0x0A]);
    image_size    = *(int *)&(header [0x22]);
    width         = *(int *)&(header [0x12]);
    height        = *(int *)&(header [0x16]);

    if (image_size == 0)
        image_size = width * height * 3;
    if (data_position == 0)
        data_position = 54;

    data = (unsigned char *) malloc (sizeof (unsigned char) * image_size);
    fread (data, sizeof (char), image_size, file);
    free (data);
    fclose (file);

    GLuint texture_id;
    glGenTextures (1, &texture_id);
    glBindTexture (GL_TEXTURE_2D, texture_id);

    glTexImage2D (GL_TEXTURE_2D, 0, 3, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
    glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    return texture_id;
}

I tried using different parameters in glTexImage2D and glTexParameteri functions, but still it change nothing. Here's the render scene function:

void RenderScene (int arg)
{
    static GLuint texture_id = CreateTextureFromBMP ("cube_blue.bmp");

    glEnable (GL_TEXTURE_2D);
    glEnableClientState (GL_TEXTURE_COORD_ARRAY);
    glEnableClientState (GL_VERTEX_ARRAY);
    glActiveTexture (GL_TEXTURE0);

    GLfloat vertices  [] = { ... };
    GLfloat texcoords [] = { ... };
    GLubyte indices   [] = { ... };

    glVertexPointer   (3, GL_FLOAT, 0, vertices);
    glTexCoordPointer (2, GL_FLOAT, 0, texcoords);

    glPushMatrix ();
        glBindTexture   (GL_TEXTURE_2D, texture_id);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

        glColor3f (1.0f, 1.0f, 1.0f);
        glDrawElements (GL_QUADS, 24, GL_UNSIGNED_BYTE, indices);
    glPopMatrix ();

    glDisable (GL_TEXTURE_2D);
    glDisableClientState (GL_TEXTURE_COORD_ARRAY);
    glDisableClientState (GL_VERTEX_ARRAY);
}

Any ideas where to look for the mistake?

CodePudding user response：

I can see an error in your code which could cause the problem you're seeing.

data = (unsigned char *) malloc (sizeof (unsigned char) * image_size);
fread (data, sizeof (char), image_size, file);
free (data);

You are allocating a buffer, reading into it, then immediately freeing it. This means that any code between free() and glTexImage2D() is free to overwrite this buffer in the heap.

Try moving the call to free() until after the call to glTexImage2D() and see what happens.