glGetTexLevelParameteriv

glGetTexLevelParameter: man3/glGetTexLevelParameter.xml

glGetTexLevelParameter returns in params texture parameter values for a specific level-of-detail value, specified as level. target defines the target texture, either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D, GL_PROXY_TEXTURE_1D, GL_PROXY_TEXTURE_2D, GL_PROXY_TEXTURE_3D, GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEXTURE_CUBE_MAP_POSITIVE_Z, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or GL_PROXY_TEXTURE_CUBE_MAP. GL_MAX_TEXTURE_SIZE, and GL_MAX_3D_TEXTURE_SIZE are not really descriptive enough. It has to report the largest square texture image that can be accommodated with mipmaps but a long skinny texture, or a texture without mipmaps may easily fit in texture memory. The proxy targets allow the user to more accurately query whether the GL can accommodate a texture of a given configuration. If the texture cannot be accommodated, the texture state variables, which may be queried with glGetTexLevelParameter, are set to 0. If the texture can be accommodated, the texture state values will be set as they would be set for a non-proxy target. pname specifies the texture parameter whose value or values will be returned. The accepted parameter names are as follows:

If an error is generated, no change is made to the contents of params. glGetTexLevelParameter returns the texture level parameters for the active texture unit.