Creates GL texture from image in file in format supported by Imaging.

function LoadGLTextureFromFile(const FileName: string; 
                               CreatedWidth: PLongInt = nil; 
                               CreatedHeight: PLongInt = nil): GLuint;

ImagingOpenGL (at line 92)

You can use CreatedWidth and Height parameters to query dimensions of created textures (it could differ from dimensions of source image).