glGetRenderbufferParameteriv

glGetRenderbufferParameter: man3/glGetRenderbufferParameter.xml

glGetRenderbufferParameteriv retrieves information about a bound renderbuffer object. target specifies the target of the query operation and must be GL_RENDERBUFFER. pname specifies the parameter whose value to query and must be one of GL_RENDERBUFFER_WIDTH, GL_RENDERBUFFER_HEIGHT, GL_RENDERBUFFER_INTERNAL_FORMAT, GL_RENDERBUFFER_RED_SIZE, GL_RENDERBUFFER_GREEN_SIZE, GL_RENDERBUFFER_BLUE_SIZE, GL_RENDERBUFFER_ALPHA_SIZE, GL_RENDERBUFFER_DEPTH_SIZE, GL_RENDERBUFFER_DEPTH_SIZE, GL_RENDERBUFFER_STENCIL_SIZE, or GL_RENDERBUFFER_SAMPLES. Upon a successful return from glGetRenderbufferParameteriv, if pname is GL_RENDERBUFFER_WIDTH, GL_RENDERBUFFER_HEIGHT, GL_RENDERBUFFER_INTERNAL_FORMAT, or GL_RENDERBUFFER_SAMPLES, then params will contain the width in pixels, the height in pixels, the internal format, or the number of samples, respectively, of the image of the renderbuffer currently bound to target. If pname is GL_RENDERBUFFER_RED_SIZE, GL_RENDERBUFFER_GREEN_SIZE, GL_RENDERBUFFER_BLUE_SIZE, GL_RENDERBUFFER_ALPHA_SIZE, GL_RENDERBUFFER_DEPTH_SIZE, or GL_RENDERBUFFER_STENCIL_SIZE, then params will contain the actual resolutions (not the resolutions specified when the image array was defined) for the red, green, blue, alpha depth, or stencil components, respectively, of the image of the renderbuffer currently bound to target.