At each level, each texel in the halved mipmap level is an average of the corresponding two texels in the larger mipmap level. Level 0 is a copy of data . These correspond to levels 0 through 6, respectively. See the glTexImage1D subroutine for a description of the acceptable values for the format parameter. See the glDrawPixels subroutine for acceptable values for the type parameter.
Parameters target Specifies the target texture.
This can be derived indirectly via glGetTexLevelParameter . First, query for the width actually used at level 0. OpenGL Overview .