218 lines
8.6 KiB
Python
218 lines
8.6 KiB
Python
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#!/usr/bin/env python3
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import math
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import inkex
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from inkex.transforms import Transform
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class IsometricProjection(inkex.EffectExtension):
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"""
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Convert a flat 2D projection to one of the three visible sides in an
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isometric projection, and vice versa.
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"""
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attrTransformCenterX = inkex.addNS('transform-center-x', 'inkscape')
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attrTransformCenterY = inkex.addNS('transform-center-y', 'inkscape')
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# Precomputed values for sine, cosine, and tangent of 30°.
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rad_30 = math.radians(30)
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cos_30 = math.cos(rad_30)
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sin_30 = 0.5 # No point in using math.sin for 30°.
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tan_30 = math.tan(rad_30)
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# Combined affine transformation matrices. The bottom row of these 3×3
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# matrices is omitted; it is always [0, 0, 1].
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transformations = {
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# From 2D to isometric top down view:
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# * scale vertically by cos(30°)
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# * shear horizontally by -30°
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# * rotate clock-wise 30°
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'to_top': [[cos_30, -cos_30, 0],
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[sin_30, sin_30, 0]],
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# From 2D to isometric left-hand side view:
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# * scale horizontally by cos(30°)
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# * shear vertically by -30°
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'to_left': [[cos_30, 0, 0],
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[sin_30, 1, 0]],
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# From 2D to isometric right-hand side view:
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# * scale horizontally by cos(30°)
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# * shear vertically by 30°
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'to_right': [[cos_30, 0, 0],
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[-sin_30, 1, 0]],
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# From isometric top down view to 2D:
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# * rotate counter-clock-wise 30°
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# * shear horizontally by 30°
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# * scale vertically by 1 / cos(30°)
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'from_top': [[tan_30, 1, 0],
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[-tan_30, 1, 0]],
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# From isometric left-hand side view to 2D:
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# * shear vertically by 30°
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# * scale horizontally by 1 / cos(30°)
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'from_left': [[1 / cos_30, 0, 0],
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[-tan_30, 1, 0]],
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# From isometric right-hand side view to 2D:
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# * shear vertically by -30°
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# * scale horizontally by 1 / cos(30°)
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'from_right': [[1 / cos_30, 0, 0],
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[tan_30, 1, 0]]
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}
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def add_arguments(self, pars):
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pars.add_argument('--conversion', default='top', help='Conversion to perform: (top|left|right)')
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pars.add_argument('--reverse', type=inkex.Boolean, default=False, help='Reverse the transformation from isometric projection to flat 2D')
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self.arg_parser.add_argument('--orthoangle', type=float, default=15.0, help='Isometric angle in degrees')
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def __initConstants(self, angle):
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# Precomputed values for sine, cosine, and tangent of orthoangle.
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self.rad = math.radians(angle)
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self.cos = math.cos(self.rad)
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self.sin = math.sin(self.rad)
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self.tan = math.tan(self.rad)
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# Combined affine transformation matrices. The bottom row of these 3×3
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# matrices is omitted; it is always [0, 0, 1].
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self.transformations = {
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# From 2D to isometric top down view:
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# * scale vertically by cos(∠)
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# * shear horizontally by -∠
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# * rotate clock-wise ∠
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'to_top': Transform(((self.cos, -self.cos, 0),
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(self.sin, self.sin, 0))),
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# From 2D to isometric left-hand side view:
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# * scale horizontally by cos(∠)
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# * shear vertically by -∠
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'to_left': Transform(((self.cos, 0, 0),
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(self.sin, 1, 0))),
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# From 2D to isometric right-hand side view:
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# * scale horizontally by cos(∠)
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# * shear vertically by ∠
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'to_right': Transform(((self.cos , 0, 0),
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(-self.sin, 1, 0))),
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# From isometric top down view to 2D:
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# * rotate counter-clock-wise orthoangle
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# * shear horizontally by orthoangle
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# * scale vertically by 1 / cos(orthoangle)
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'from_top': [[self.tan , 1, 0],
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[-self.tan, 1, 0]],
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# From isometric left-hand side view to 2D:
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# * shear vertically by orthoangle
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# * scale horizontally by 1 / cos(orthoangle)
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'from_left': [[1 / self.cos, 0, 0],
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[-self.tan, 1, 0]],
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# From isometric right-hand side view to 2D:
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# * shear vertically by -orthoangle
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# * scale horizontally by 1 / cos(orthoangle)
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'from_right': [[1 / self.cos, 0, 0],
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[self.tan, 1, 0]]
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}
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# The inverse matrices of the above perform the reverse transformations.
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self.transformations['from_top'] = -self.transformations['to_top']
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self.transformations['from_left'] = -self.transformations['to_left']
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self.transformations['from_right'] = -self.transformations['to_right']
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def getTransformCenter(self, midpoint, node):
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"""
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Find the transformation center of an object. If the user set it
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manually by dragging it in Inkscape, those coordinates are used.
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Otherwise, an attempt is made to find the center of the object's
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bounding box.
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"""
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c_x = node.get(self.attrTransformCenterX)
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c_y = node.get(self.attrTransformCenterY)
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# Default to dead-center.
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if c_x is None:
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c_x = 0.0
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else:
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c_x = float(c_x)
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if c_y is None:
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c_y = 0.0
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else:
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c_y = float(c_y)
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x = midpoint[0] + c_x
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y = midpoint[1] - c_y
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return [x, y]
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def translateBetweenPoints(self, tr, here, there):
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"""
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Add a translation to a matrix that moves between two points.
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"""
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x = there[0] - here[0]
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y = there[1] - here[1]
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tr.add_translate(x, y)
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def moveTransformationCenter(self, node, midpoint, center_new):
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"""
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If a transformation center is manually set on the node, move it to
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match the transformation performed on the node.
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"""
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c_x = node.get(self.attrTransformCenterX)
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c_y = node.get(self.attrTransformCenterY)
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if c_x is not None:
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x = str(center_new[0] - midpoint[0])
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node.set(self.attrTransformCenterX, x)
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if c_y is not None:
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y = str(midpoint[1] - center_new[1])
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node.set(self.attrTransformCenterY, y)
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def effect(self):
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self.__initConstants(self.options.orthoangle)
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if self.options.reverse is True:
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conversion = "from_" + self.options.conversion
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else:
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conversion = "to_" + self.options.conversion
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if len(self.svg.selected) == 0:
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inkex.errormsg("Please select an object to perform the " +
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"isometric projection transformation on.")
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return
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# Default to the flat 2D to isometric top down view conversion if an
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# invalid identifier is passed.
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effect_matrix = self.transformations.get(
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conversion, self.transformations.get('to_top'))
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for id, node in self.svg.selected.items():
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bbox = node.bounding_box()
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midpoint = [bbox.center_x, bbox.center_y]
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center_old = self.getTransformCenter(midpoint, node)
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transform = Transform(node.get("transform"))
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# Combine our transformation matrix with any pre-existing transform.
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tr = transform @ effect_matrix
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# Compute the location of the transformation center after applying
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# the transformation matrix.
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center_new = center_old[:]
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#Transform(matrix).apply_to_point(center_new)
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tr.apply_to_point(center_new)
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tr.apply_to_point(midpoint)
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# Add a translation transformation that will move the object to
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# keep its transformation center in the same place.
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self.translateBetweenPoints(tr, center_new, center_old)
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node.set('transform', str(tr))
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# Adjust the transformation center.
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self.moveTransformationCenter(node, midpoint, center_new)
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if __name__ == '__main__':
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IsometricProjection().run()
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