Logical Size, and Aspect Ratio

An ePiX figure occupies a rectangular Cartesian ``bounding box''. The lower left and upper right corners of the bounding box are known to ePiX as (x_min,y_min) and (x_max,y_max), while the width and height are x_size and y_size. The bounding box is a virtual, advisory data structure; its dimensions are not directly related to the figure's printed size, and picture elements are not constrained to the bounding box by default.

The bounding box is specified in the preamble by giving a pair of opposite corners; the command

  bounding_box(P(-1,0), P(3,2));

sets the bounding box to be $[-1,3]\times[0,2]$. Either pair of opposite corners may be used, though confusion is less likely if the lower left and upper right corners are given. Affine scaling maps the bounding box to the picture box when the output file is written:

The figure's aspect ratio is controlled by sizing the bounding box. The aspect ratio is ``true'' if the bounding box and picture box are geometrically similar, e.g., if both boxes are 1.5 times as wide as they are tall.