Merge pull request #187 from lexelby/lexelby-realistic-rendering

realistic rendering

1 files changed, 129 insertions, 0 deletions

diff --git a/lib/svg/realistic_rendering.py b/lib/svg/realistic_rendering.py
new file mode 100644
index 00000000..e31534da
--- /dev/null
+++ b/lib/svg/realistic_rendering.py
@@ -0,0 +1,129 @@
+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)