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return aspect_block.value(row,col)
#-----------Given a slope, find the ideal spacing of hachures-----------
def ideal_spacing(slope):
if slope > max_slope:
slope = max_slope
elif slope < min_slope:
# None indicates that slope is too shallow & needs no hachures
return None
# Finds where the slop is in the range of min/max slope
# Then normalizes it to the range of min/max spacing
slope_pct = (slope - min_slope) / slope_range
spacing_qty = slope_pct * spacing_range
spacing = max_spacing - spacing_qty
return spacing
#--Take Segments & turn them into dashed lines based on ideal spacing---
def dash_maker(contour_segment_list):
output_segments = []
for contour_segment in contour_segment_list:
slope = contour_segment.slope
if slope < min_slope:
continue
spacing = ideal_spacing(slope)
#We tune the spacing value based on the segment length to ensure
#an integer number of dashes. This is rather like the automatic
#dash/gap spacing in Adobe Illustrator
#Our goal here is to split a segment into dashes & gaps, thusly:
# ---- ---- ---- ---- ---- ---- ----
#Each dash length = spacing, surrounded by gaps half that width
#Thus one unit looks like this: | ---- |
total_length = spacing * 2 #the length of a gap + dash + gap
total_units = round(contour_segment.length / total_length)
if total_units == 0:
#Just in case we round down to the point of having 0 dashes
continue
dash_gap_length = contour_segment.length / total_units
dash_width = dash_gap_length / 2
#half of our gap-dash-gap is the dash
gap_width = dash_width / 2
start_point = gap_width
end_point = dash_width + gap_width
geometry = contour_segment.geometry
while True:
substring_feature = QgsFeature()
line_substring = geometry.constGet().curveSubstring(
start_point, end_point)
substring_feature.setGeometry(line_substring)
output_segments.append(Segment(substring_feature))
start_point += dash_gap_length
end_point += dash_gap_length
if end_point > contour_segment.length:
break
if len(output_segments) > 0:
return output_segments
else:
return None
#-------------------Starts our first set of hachures--------------------
def first_contour(contour):
global current_hachures
# Split the contour into even segments to begin
contour_segments = even_splitter(contour)
# Then turn them into dashes
dashes = dash_maker(contour_segments)
if dashes:
current_hachures = hachure_generator(dashes)
#----Checks a contour to see where hachures need to be trimmed/begun----
def subsequent_contour(contour):
global current_hachures
# First we split the contour according to the existing hachures
split_contour = contour.split_by_hachures()
# We may need to further subdivide some of these. Some segments may