Module bbox

The bbox module defines axis-aligned bounding boxes (bbox, bbox_pt, and empty) used throughout PyX to compute the spatial extent of paths, text boxes, canvases, and pages. While you most commonly obtain a bounding box by calling an object’s bbox() method (such as canvas.canvas.bbox() or path.path.bbox()), you can also construct and manipulate bounding boxes directly—for example, to pass a custom clipping or page bounding box to canvas.canvas.writeEPSfile() or document.page.

Constructing Bounding Boxes

class bbox.bbox(llx, lly, urx, ury)

Constructs a bounding box with lower-left corner (llx, lly) and upper-right corner (urx, ury) specified in user units or PyX lengths.

class bbox.bbox_pt(llx_pt, lly_pt, urx_pt, ury_pt)

Constructs a bounding box with coordinates (llx_pt, lly_pt) and (urx_pt, ury_pt) specified directly in PostScript points. All bbox() methods on PyX objects return bbox_pt instances.

class bbox.empty

Constructs an empty bounding box (containing no points, with llx_pt=None). An empty bounding box evaluates to False in a boolean context (bool(bbox.empty()) == False), whereas any non-empty bounding box evaluates to True.

Set Operations and Methods

Two bounding boxes b1 and b2 can be combined using arithmetic operators:

• Union (b1 + b2 or b1 += b2): Returns the smallest bounding box enclosing both b1 and b2. Adding an empty bounding box leaves the other bounding box unchanged.

• Intersection (b1 * b2 or b1 *= b2): Returns the overlapping region of b1 and b2 (or an empty bounding box if either input is empty).

In addition, bbox and bbox_pt provide the following methods (where measurement methods without a _pt suffix return true PyX lengths unit.t_pt, and _pt variants take or return plain floats in PostScript points):

Method	Description
copy()	Returns a copy of the bounding box.
set(other)	Copies the coordinates of other into self.
intersects(other)	Returns True if self and other overlap (and neither is empty), or False/0 otherwise.
includepoint_pt(x_pt, y_pt)	Expands self in place to include the point (x_pt, y_pt).
transform(trafo)	Transforms the four corners of self in place by trafo and updates self to their enclosing axis-aligned box.
transformed(trafo)	Returns a new bounding box enclosing self after transformation by trafo.
enlarge(all=0, bottom=None, left=None, top=None, right=None)	Expands self in place on each side by the specified PyX lengths (using all for any side left as None). Also available as enlarge_pt(...).
enlarged(all=0, bottom=None, left=None, top=None, right=None)	Returns a new bounding box expanded on each side by the specified amounts (using all for any side left as None). Also available as enlarged_pt(...).
path() / rect()	Returns a rectangular path.rect_pt path tracing the boundary of the bounding box.
width() / width_pt()	Returns the horizontal width of the bounding box.
height() / height_pt()	Returns the vertical height of the bounding box.
left() / left_pt()	Returns the x-coordinate of the left edge (llx).
right() / right_pt()	Returns the x-coordinate of the right edge (urx).
bottom() / bottom_pt()	Returns the y-coordinate of the bottom edge (lly).
top() / top_pt()	Returns the y-coordinate of the top edge (ury).
center() / center_pt()	Returns the (x, y) coordinates of the center of the bounding box.
lowrestuple_pt()	Returns (floor(llx_pt), floor(lly_pt), ceil(urx_pt), ceil(ury_pt)) as integer points (used for PostScript %%BoundingBox).
highrestuple_pt()	Returns (llx_pt, lly_pt, urx_pt, ury_pt) in exact floating-point points (used for %%HiResBoundingBox).