I have a Texture program,after i am choosing a texture to a part of my 3D object,the object is becoming dark.
How can make the object to be in the same lighting as it was before my texture mapping?

Thanks a lot …

This Texture program is a fragment program ?
or you are toalking about the standar opengl lighting ?

Its aprogram that is based on standart opengl lighting .

Does this help?

So try checking the material proprieties and lighting propriety(ambient, diffuse and specular) values
then change them until you got the result you desire