How to place figure in the absolute top position?

I'm using IEEE conference style spconf.sty

My question is, how to place a figure in the absolute top position in a page, and leaving no space on the top or left or right.

For example, the figure below:

the red area is the original figure.

How do I span it to blue area? Or green area?

The current code for the figure is:

\begin{figure*}[!t]
\centering
\includegraphics[width=0.8\textwidth]{figures/aaa}
\caption{aaa}
\label{aaa}
\end{figure*}

• If this is for a conference, don't do it. They may decide to add a header. If not, you can use \makebox[\textwidth][c]{\vskip*{\dimexpr -1in-\topmargin-\headheight-\headsep}...} – John Kormylo Apr 18 '18 at 15:00
• @JohnKormylo This is for conference, but they wont't add anything in the header, so it is okay. Where should I insert this code? – Nathan Explosion Apr 19 '18 at 12:23

There appears to be a slight gap left. It is smaller than \topskip or \dblfloatsep or \dbltextfloatsep, so it probably isn't deliberate.

\documentclass[conference]{IEEEtran}
\usepackage{graphicx}
\usepackage{lipsum}

\begin{document}
\begin{figure*}[tp]% AFAICT, adding ! does nothing useful