Is there a set of constants for unit conversion?

[jrom99]

I want to draw a circle with a given radius, is there a function or constant available for use? Currently I"m using this:

def as_dist(v, unit="mm"):
    p0 = fitz.Point(0,0)
    p1 = fitz.Point(1,0)
    unitary_dist = 1/(p0.distance_to(p1, unit))
    return v*unitary_dist

mm = as_dist(1, "mm")

Is there some constant or function within pymupdf itself for this?

from fitz import mm
Page.draw_circle(center, radius=2*mm)
# or
from fitz import as_dist
Page.draw_circle(center, radius=as_dist(2, "mm"))

[JorjMcKie]

No, there is not.
Please simply use 1 inch = 72 points = 25.4 mm

[JorjMcKie]

PyMuPDF views these types of constants as parts of some general module.
Would be a never ending story, too. Questions for area units would not be farfteched, too, would they.
But there are standard page sizes recorded like Letter or ISO-A4: fitz.paper_size() and friends.

[jrom99]

I see, thanks for the info. I fail to see use cases that would need area constants, though. (I can't remember any function in pymupdf that accepts an area as an argument, are there many of them?)

As for units, I think mm, cm and inch would cover enough use cases to justify being the only ones defined, especially when dealing with paddings and margins.

[JorjMcKie]

accepts an area as an argument

Well, I have been alluding to the various page rectangles primarily. Rectangles / bboxes appear all over the place in PyMuPDF. They always are defined in point units (1 in = 72 pt).
At least in PDF, "real world" units like inch, foot, yard, m, cm, mm play no role at all, and I believe you will not find a single referral to them in the PDF spec ... and neither in MuPDF.

Some examples for standard page / rectangle sizes (I recall there are more than a dozen):

import fitz
fitz.paper_size("a4")
(595, 842)
fitz.paper_size("letter")
(612, 792)
fitz.paper_rect("a4")
Rect(0.0, 0.0, 595.0, 842.0)
fitz.paper_rect("letter")
Rect(0.0, 0.0, 612.0, 792.0)

Whether you insert an image or an annotation, and many other things: rectangles are the most frequent arguments. Similarly for extracting stuff.

There are a select few functions in PyMuPDF which return other units than points:

r = fitz.paper_rect("a4")
r.get_area("cm")  # other options: "mm" = millimeter, "in" = inch, "px" = point (default)
623.4928788580246
p1 = fitz.Point(0,0)
p2 = fitz.Point(1,1)
p1.distance_to(p2, "cm")
0.04989031178371752
p1.distance_to(p2, "in")
0.019641855032959652
p1.distance_to(p2, "px")
1.4142135623730951
p1.distance_to(p2, "mm")
0.49890311783717517

I think the above should serve your purpose.

[JorjMcKie]

But if you do have a PR that implements a function similar to fitz.from_unit(2, "cm"), I would welcome it and integrate it in the next version.
The example would mean that 2 is given in centimeters and should be converted to "pt".