AA Leaders#

AA Leader Properties#

im
PIL image handle, link to the calling program
dr
PIL drawing handle, link to the calling program
at
Coordinates on object
angle
Angle of first extension line, changes leader orientation
extA
Length inclined extension line, default 20
extB
Length horizontal extension line, default 20
text
Dimension text
font
Font of the text
fill
Line colour, RGB tuple
back
Background colour, RGB tuple
arrowhead
Three integer tuple describing the shape and size of the arrow
arrow
position of the arrow on the line, which influences the direction it points.

Upper Leader

Lower Leader

Left position
225°

Right position
315°

Left position
135°

Right position
45°

Upper Leader	Lower Leader

Left position 225°	Right position 315°	Left position 135°	Right position 45°

Leaders allow us to refer to a specific item property not easily shown by normal dimensions or general decriptive notes.

The leader example has a single arrow on an angled line with a horizontal line over which the text is placed.

Changing the angle gives different leader orientations. It is better to use angles between 30 and 60° in each of the quadrants.

import sys
sys.path.append('../dims')

from PIL import Image, ImageDraw, ImageFont
from DimLinesAA import LineAA, dimension_aa
from DimLinesPIL import angled_text, polar2cart


def leader_aa(im, dr, at, angle=315, extA=20, extB=20, arrowhead=(3,5,1),
            arrow='first', fill=(0,0,0), text=None, font=None, back=(255,255,221)):
    # leader to object, angle and length (extA) first part, then goes horizontal
    # for second part (extB). Only one arrow where leader points.
    # start at,

    #font = ImageFont.load_default() if font is None else font
    font = font if font else ImageFont.load_default()
    # (wide, height) = font.getsize(text)
    unused1, unused2, wide, height = font.getbbox(text)

    h = height // 2

    if wide > extB:
        print('extB was increased from:',extB,'to accommodate the text',wide+10)
        extB = wide+10

    # dimension line
    phi = 180 if 90 < angle < 270 else 0
    ptB = polar2cart(at, angle, extA)
    ptC = polar2cart(ptB, phi, extB)
    ptD = polar2cart(at, angle, arrowhead[0])
    dimension_aa(im, dr, at, ptB, arrowhead=arrowhead,
              arrow=arrow, fill=fill, back=back)
    LineAA(dr, ptB, ptC, fill=fill, back=back)
    LineAA(dr, ptB, ptD, fill=fill, back=back)

    # text position
    tp = ((ptB[0] + ptC[0])//2, ptB[1] - h - 5)

    angled_text(im, tp, text, 0, font)

if __name__ == "__main__":
    Text = 'Test' #'y+ε+m'

    Font = ImageFont.truetype('consola.ttf', 12)
    # (wi, ht) = Font.getsize(Text)
    unused1, unused2, wi, ht = Font.getbbox(Text)

    eb = wi + 10
    Back = (255,255,221)
    image2 = Image.new('RGB', (120, 120), Back)
    # Get drawing context
    ldraw = ImageDraw.Draw(image2)

    lat = (80, 50)
    a = 135
    Fill = (0,0,0)
    leader_aa(image2, ldraw, lat, angle=a, extB=40, text=Text, font=Font,
            fill=Fill, back=Back)

    image2.show()
    #image2.save('../../temp/leader'+str(a)+'.png')

AA Leaders#

AA Leader Properties#

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