The illustration of the ellipse parameters. QianZhi-Ming En ChengXi Qiu ChenYan 2014 <p>(a) The raw image of the fish head region; (b) (<i>x</i><sub>o</sub>,<i>y</i><sub>o</sub>) denotes the extreme point and the violet color shows the grayscale distribution of the extreme point region. Variables <i>length</i>, <i>width</i> and represent the long axis, short axis and angle of the fitted ellipse respectively; (c) The variable <i>contrast</i> in the direction of the z-axis represents the contrast change of the ellipse and its surrounding region.</p>