Using PyX, how can I set the size of the canvas?

Question

Beginner's question using PyX in Python 3.8.1.

I'm creating an EPS file, and would like the canvas size to be 70 mm x 70 mm. How can I do this?

from pyx import *
# build and size canvas
c = canvas.canvas()
c.fill(path.circle(2.5, 1.5, 0.5))
c.writeEPSfile("my-output")
print("Done!")

The .eps file that I get is the size of the element that I've added, but I would like it to be a 70 mm square. Any help appreciated!

Answer 1

The bounding box is a property of the page (see document.page). In the writeEPSfile method page parameters can be set by the page_ prefix (see writeEPSfile documentation), hence the following code creates the requested output:

from pyx import *
from pyx import bbox
# build and size canvas
c = canvas.canvas()
c.fill(path.circle(2.5, 1.5, 0.5))
c.writeEPSfile("my-output", page_bbox=bbox.bbox(0, 0, 7, 7))
print("Done!")

Note that the bbox module is not part of the default module names imported by *, thus a second import line is required.

Answer 2

Thank you, this worked well! My image is in different orientations, so I ended up with:

if blnFlip == True:
        MasterCanvas.items[i].writeEPSfile("my_output", page_bbox=bbox.bbox(llx_pt=-CanvasSizeCm, lly_pt=-CanvasSizeCm, urx_pt=0, ury_pt=0))
else:
        MasterCanvas.items[i].writeEPSfile("my_output", page_bbox=bbox.bbox(llx_pt=0, lly_pt=-CanvasSizeCm, urx_pt=CanvasSizeCm, ury_pt=0))