SVG export enhancements

Add option to set scaling based on model dimension instead of autoscale.
Change default projection to match cq-editor.
Add option and set default "up" direction so it does not flip with changes to projectionDir.
Remove margin from autoscale calculation when autoscale enabled.  This allows margins to be edited without affecting scale.

cadquery/occ_impl/exporters/svg.py

@@ -1,7 +1,7 @@
 import io as StringIO
 
 from ..shapes import Shape, Compound, TOLERANCE
-from ..geom import BoundBox
+from ..geom import BoundBox, Vector
 
 
 from OCP.gp import gp_Ax2, gp_Pnt, gp_Dir
@@ -20,7 +20,7 @@
    height="%(height)s"
 
 >
-    <g transform="scale(%(unitScale)s, -%(unitScale)s)   translate(%(xTranslate)s,%(yTranslate)s)" stroke-width="%(strokeWidth)s"  fill="none">
+    <g transform="translate(%(xTranslate)s,%(yTranslate)s) scale(%(unitScale)s, -%(unitScale)s)" stroke-width="%(strokeWidth)s"  fill="none">
        <!-- hidden lines -->
        <g  stroke="rgb(%(hiddenColor)s)" fill="none" stroke-dasharray="%(strokeWidth)s,%(strokeWidth)s" >
 %(hiddenContent)s
@@ -137,9 +137,11 @@ def getSVG(shape, opts=None):
         height: Document height of the resulting image.
         marginLeft: Inset margin from the left side of the document.
         marginTop: Inset margin from the top side of the document.
+        viewHeight: Height in model units.  Used to set scale.
         projectionDir: Direction the camera will view the shape from.
+        up: Up direction. Default (0, 0, 1).
         showAxes: Whether or not to show the axes indicator, which will only be
-                  visible when the projectionDir is also at the default.
+            visible when the projectionDir is also at the default.
         strokeWidth: Width of the line that visible edges are drawn with.
         strokeColor: Color of the line that visible edges are drawn with.
         hiddenColor: Color of the line that hidden edges are drawn with.
@@ -152,7 +154,9 @@ def getSVG(shape, opts=None):
         "height": 240,
         "marginLeft": 200,
         "marginTop": 20,
-        "projectionDir": (-1.75, 1.1, 5),
+        "viewHeight": None,
+        "projectionDir": (1, -1, 1),
+        "up": (0, 0, 1),
         "showAxes": True,
         "strokeWidth": -1.0,  # -1 = calculated based on unitScale
         "strokeColor": (0, 0, 0),  # RGB 0-255
@@ -170,6 +174,7 @@ def getSVG(shape, opts=None):
     height = float(d["height"])
     marginLeft = float(d["marginLeft"])
     marginTop = float(d["marginTop"])
+    viewHeight = float(d["viewHeight"]) if d.get("viewHeight") else None
     projectionDir = tuple(d["projectionDir"])
     showAxes = bool(d["showAxes"])
     strokeWidth = float(d["strokeWidth"])
@@ -180,7 +185,13 @@ def getSVG(shape, opts=None):
     hlr = HLRBRep_Algo()
     hlr.Add(shape.wrapped)
 
-    projector = HLRAlgo_Projector(gp_Ax2(gp_Pnt(), gp_Dir(*projectionDir)))
+    vx = Vector(d["up"]).cross(Vector(projectionDir))
+    if vx.Length < 1e-6:
+        projector = HLRAlgo_Projector(gp_Ax2(gp_Pnt(), gp_Dir(*projectionDir)))
+    else:
+        projector = HLRAlgo_Projector(
+            gp_Ax2(gp_Pnt(), gp_Dir(*projectionDir), gp_Dir(*vx.toTuple()))
+        )
 
     hlr.Projector(projector)
     hlr.Update()
@@ -227,13 +238,17 @@ def getSVG(shape, opts=None):
     bb = Compound.makeCompound(hidden + visible).BoundingBox()
 
     # width pixels for x, height pixels for y
-    unitScale = min(width / bb.xlen * 0.75, height / bb.ylen * 0.75)
-
-    # compute amount to translate-- move the top left into view
-    (xTranslate, yTranslate) = (
-        (0 - bb.xmin) + marginLeft / unitScale,
-        (0 - bb.ymax) - marginTop / unitScale,
-    )
+    if viewHeight is not None:
+        unitScale = height / viewHeight
+        xTranslate = width / 2
+        yTranslate = height / 2
+    else:
+        unitScale = min((width / bb.xlen * 0.75, height / bb.ylen * 0.75))
+        # compute amount to translate-- move the top left into view
+        (xTranslate, yTranslate) = (
+            marginLeft - bb.xmin * unitScale,
+            marginTop + bb.ymax * unitScale,
+        )
 
     # If the user did not specify a stroke width, calculate it based on the unit scale
     if strokeWidth == -1.0:

tests/test_cadquery.py

@@ -111,7 +111,7 @@ def testToSVG(self):
         """
         r = Workplane("XY").rect(5, 5).extrude(5)
 
-        r_str = r.toSvg()
+        r_str = r.toSvg({"projectionDir": (-1.75, 1.1, 5)})
 
         # Make sure that a couple of sections from the SVG output make sense
         self.assertTrue(r_str.index('path d="M') > 0)