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import simplepath
import math
from .units import PIXELS_PER_MM
from ..utils import cache, Point
# The stitch vector path looks like this:
# _______
# (_______)
#
# It's 0.32mm high, which is the approximate thickness of common machine
# embroidery threads.
# 1.216 pixels = 0.32mm
stitch_height = 1.216
# This vector path starts at the upper right corner of the stitch shape and
# proceeds counter-clockwise.and contains a placeholder (%s) for the stitch
# length.
#
# It contains two invisible "whiskers" of zero width that go above and below
# to ensure that the SVG renderer allocates a large enough canvas area when
# computing the gaussian blur steps. Otherwise, we'd have to expand the
# width and height attributes of the <filter> tag to add more buffer space.
# The width and height are specified in multiples of the bounding box
# size, It's the bounding box aligned with the global SVG canvas's axes, not
# the axes of the stitch itself. That means that having a big enough value
# to add enough padding on the long sides of the stitch would waste a ton
# of space on the short sides and significantly slow down rendering.
stitch_path = "M0,0c0.4,0,0.4,0.3,0.4,0.6c0,0.3,-0.1,0.6,-0.4,0.6v0.2,-0.2h-%sc-0.4,0,-0.4,-0.3,-0.4,-0.6c0,-0.3,0.1,-0.6,0.4,-0.6v-0.2,0.2z"
# This filter makes the above stitch path look like a real stitch with lighting.
realistic_filter = """
<filter
style="color-interpolation-filters:sRGB"
id="realistic-stitch-filter"
x="-0.1"
width="1.2"
y="-0.1"
height="1.2">
<feGaussianBlur
stdDeviation="1.5"
id="feGaussianBlur1542-6"
in="SourceAlpha" />
<feComponentTransfer
id="feComponentTransfer1544-7"
result="result1">
<feFuncR
id="feFuncR1546-5"
type="identity" />
<feFuncG
id="feFuncG1548-3"
type="identity" />
<feFuncB
id="feFuncB1550-5"
type="identity"
slope="4.5300000000000002" />
<feFuncA
id="feFuncA1552-6"
type="gamma"
slope="0.14999999999999999"
intercept="0"
amplitude="3.1299999999999999"
offset="-0.33000000000000002" />
</feComponentTransfer>
<feComposite
in2="SourceAlpha"
id="feComposite1558-2"
operator="in" />
<feGaussianBlur
stdDeviation="0.089999999999999997"
id="feGaussianBlur1969" />
<feMorphology
id="feMorphology1971"
operator="dilate"
radius="0.10000000000000001" />
<feSpecularLighting
id="feSpecularLighting1973"
result="result2"
specularConstant="0.70899999"
surfaceScale="30">
<fePointLight
id="fePointLight1975"
z="10" />
</feSpecularLighting>
<feGaussianBlur
stdDeviation="0.040000000000000001"
id="feGaussianBlur1979" />
<feComposite
in2="SourceGraphic"
id="feComposite1977"
operator="arithmetic"
k2="1"
k3="1"
result="result3"
k1="0"
k4="0" />
<feComposite
in2="SourceAlpha"
id="feComposite1981"
operator="in" />
</filter>
"""
def realistic_stitch(start, end):
"""Generate a stitch vector path given a start and end point."""
end = Point(*end)
start = Point(*start)
stitch_length = (end - start).length()
stitch_center = (end + start) / 2.0
stitch_direction = (end - start)
stitch_angle = math.atan2(stitch_direction.y, stitch_direction.x)
stitch_length = max(0, stitch_length - 0.2 * PIXELS_PER_MM)
# create the path by filling in the length in the template
path = simplepath.parsePath(stitch_path % stitch_length)
# rotate the path to match the stitch
rotation_center_x = -stitch_length / 2.0
rotation_center_y = stitch_height / 2.0
simplepath.rotatePath(path, stitch_angle, cx=rotation_center_x, cy=rotation_center_y)
# move the path to the location of the stitch
simplepath.translatePath(path, stitch_center.x - rotation_center_x, stitch_center.y - rotation_center_y)
return simplepath.formatPath(path)
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