In C++, OpenGL, Glut, how to bind image.c to a texture, where image.c comes from Gimp>Export>C source code

Question

So I've spent past two days looking through different kinds of 'solutions' to my question via google, there aren't all that many and the ones I've find don't seem to work.

I'm exporting a small test image as .c resource file from Gimp, it's size is 64x64 and it has an alpha channel. Basically looks like:

    static const struct {
    unsigned int     width;
    unsigned int     height;
    unsigned int     bytes_per_pixel; /* 2:RGB16, 3:RGB, 4:RGBA */ 
    char            *comment;
    unsigned char    pixel_data[64 * 64 * 4 + 1];
    } ship = {
    64, 64, 4,
    (char*) 0,
    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
    "\0\0\0\0\0\0\0\0\237\237\237\377\237\237\237\377\237\237\237\377\237\237"
    "\237\377\237\237\237\377\237\237\237\377\237\237\237\377vZI\0vZI\0vZI\0\0"
    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"

and goes on like that for quite a while, as you might expect, until finally ending with

    "\237\237\377\237\237\237\377\237\237\237\377",
    };

So how can I actually use this resource file? If anyone could provide an example, a bare minimum that is needed to create a square with the texture stamped on it, I'd be most appreciative.

That struct has all info needed to creat a texture. What is not clear? — BЈовић, Mar 06 '14 at 12:45

score 0 · Accepted Answer · edited May 23 '17 at 12:20

Looking at the reference page for glTexImage2D, it is done like (from here) :

GLuint texName1 = 0;

glGenTextures(1, &texName1);
glBindTexture(GL_TEXTURE_2D, texName1);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
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_LINEAR);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexImage2D(GL_TEXTURE_2D, 0, ship.bytes_per_pixel, ship.width, ship.height, 0, GetDataFormat(), GetDataType(), ship.pixel_data);

glColor3f(1, 1, 0);
glBindTexture(GL_TEXTURE_2D, texName1);
glBegin(GL_QUADS);
    glTexCoord2f (0.0, 0.0);
    glVertex3f (0.0, 0.0, -5.0f);
    glTexCoord2f (1.0, 0.0);
    glVertex3f (.5, 0.0, -5.0f);
    glTexCoord2f (1.0, 1.0);
    glVertex3f (.5, .5, -5.0f);
    glTexCoord2f (0.0, 1.0);
    glVertex3f (0.0, .5, -5.0f);
glEnd();

The key line is this :

glTexImage2D(GL_TEXTURE_2D, 0, ship.bytes_per_pixel, ship.width, ship.height, 0, GetDataFormat(), GetDataType(), ship.pixel_data);

You need to implement GetDataFormat() and GetDataType() yourself, and it returns the data format and type.

One possible implementation :

GLenum GetDataFormat(){
  return  GL_BGRA;
}
GLenum GetDataType(){
  return  GL_UNSIGNED_BYTE;
}

Thank you, I guess I just couldn't comprehend that glTexImage2D does everything for me. I've got it working now, except that the alpha channel does not seem to work, it's just black. Any idea what that might be about? — YellowPeak, Mar 06 '14 at 14:36
nvm, had forgotten to enable GL_BLEND. It's all working now, thank you. — YellowPeak, Mar 06 '14 at 14:42

score 0 · Answer 2 · answered Mar 06 '14 at 13:20

0

add the file to your source code. ship structure object is created with all info needed.

answered Mar 06 '14 at 13:20

squid

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In C++, OpenGL, Glut, how to bind image.c to a texture, where image.c comes from Gimp>Export>C source code

2 Answers2