Well, it is better that you have these parts separated in your essay - Introduction, Overview and the Body Parts. Accordingly, the second sentence of the above should move into the overview section. In the introduction, you should introduce the image presentation. In the overview, describe the main observations and trends very briefly. Do not have details there like figures and other data. They should go to the detailed paras.
Actually, I always try to write follow your structure your mentioned. In this essay,
the first sentence,
Given is a graph illustrating past, present, and future data about the production of world's oil on OPEC and non - OPEC countries.
I introduce the figure.
the second sentence
It is evident from the information supplied that the amount of oil production in the OPEC Middle Eastern countries is predicted to increase considerably. In stark contrast, oil production in else where is likely to fall.
I present the main observations and trends of the graph.
I think that my words in this essay it is not clear to express my idea. So, you can give me some examples which are better. Thanks you in advance.