I all, I have a little difference between my bitmap and rendering texture on screen. If my bitmap is just one color like RGB(0.128.64) then on screen I got one color (great ;-) ) but it is RGB(0.127.63) What's happening ??? Thanks a lot for any help... // Create MipMapped Texture glDeleteTextures(1, &m_texture[0]); glGenTextures(1, &m_texture[0]); glBindTexture(GL_TEXTURE_2D, m_texture[0]); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR); gluBuild2DMipmaps(GL_TEXTURE_2D, 3, m_simpleDib.m_sizeDIB.cx, m_simpleDib.m_sizeDIB.cy, GL_BGR_EXT, GL_UNSIGNED_BYTE, m_simpleDib.m_pBits); // Draw glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glPushMatrix(); glEnable(GL_TEXTURE_2D); glDisable (GL_BLEND); glDisable(GL_ALPHA_TEST); glBindTexture(GL_TEXTURE_2D, m_bkObject.m_texture[0]); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex2f(-1.0f, -1.0f); glTexCoord2f(1.0f, 0.0f); glVertex2f( 1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex2f( 1.0f, 1.0f); glTexCoord2f(0.0f, 1.0f); glVertex2f(-1.0f, 1.0f); glEnd(); glPopMatrix(); glFlush();

A bitmap stores its colours in a BGR format but OpenGL wants it in RGB, hence the colour looks wrong. There is an extension to automatically sort this out for you but I forget its name. I find it much easier to just do a byte-swap after loading the bitmap.

Happy coding.

Thanks for your answer eSCHEn but my bitmap is a Dib section with BI_RGB format. So bytes are already in the right ordrer.
In fact texture appears quite perfectly on screen exept a little difference of 1 for each RGB value...

May I have to play with these 2 functions ???
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR);

A difference of 1/255 really means nothing.
When GL uploads the data to video card, conversions MAY occur. Since GL does most computations in floating-point arithmethic (well, the model, not most implementations) it's perfectly fine to have little differences.
GL is not meant to be pixel-perfect.
So, unless you see bad artifacts, you can guess GL is doing its job.
Think this little data loss as the price you pay for speed.

Ooops, sorry Lilive, I wasn't paying attention there. That'll teach me to post full of codine with no sleep ;)

Don't worry eSCHEn, my message was not very clear ;-))
Thanks for your answer Krohm, I will make with that little loss...