First commit

README.md

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+# ridger

pyproject.toml

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+[project]
+name = "ridger"
+version = "0.1.0"
+description = "Create ridge images"
+authors = [
+    {name = "Jacopo Farina",email = "[email protected]"},
+]
+dependencies = [
+    "Pillow>=10.1.0",
+]
+requires-python = ">=3.12"
+readme = "README.md"
+license = {text = "MIT"}
+
+[build-system]
+requires = ["setuptools>=61", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[tool.pdm.dev-dependencies]
+dev = [
+    "ruff>=0.1.6",
+]

src/ridger/__init__.py

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+from typing import Callable
+
+from PIL import Image, ImageDraw
+
+IMSIZE = (1000, 1000)
+BGCOLOR = (0, 0, 0, 255)
+# distance between line in data space
+LINE_DISTANCE = 11
+# distance between data points on the same line in data space
+DATA_POINT_DISTANCE = 5
+
+
+def generate_ridge_image(
+    height_map: Callable[[int, int], int],
+    line_color: Callable[[int, int, int, int], tuple[int, int, int, int]],
+    imsize=IMSIZE,
+    bgcolor=BGCOLOR,
+    data_to_screen=lambda x, y: (x, y),
+):
+    im = Image.new("RGBA", imsize, bgcolor)
+
+    draw = ImageDraw.Draw(im)
+    for line_depth in range(LINE_DISTANCE, imsize[1], LINE_DISTANCE):
+        previous_point = None, None
+        for x in range(0, imsize[0], DATA_POINT_DISTANCE):
+            height = height_map(x, line_depth)
+            # first data point is skipped
+            if previous_point[0] is not None:
+                # draw the trapezoid that occludes the previous lines
+                draw.polygon(
+                    [
+                        # previous point, base
+                        data_to_screen(x - DATA_POINT_DISTANCE, line_depth),
+                        # previous point, with elevation
+                        data_to_screen(*previous_point),
+                        # current point, with elevation
+                        data_to_screen(x, line_depth - height),
+                        # current point, base
+                        data_to_screen(x, line_depth),
+                    ],
+                    fill=bgcolor,
+                )
+                # draw the line over the trapezoid
+                draw.line(
+                    (
+                        data_to_screen(*previous_point),
+                        data_to_screen(x, line_depth - height),
+                    ),
+                    fill=line_color(*previous_point, x, line_depth - height),
+                    width=2,
+                )
+            previous_point = x, line_depth - height
+    return im

src/ridger/examples/donut.py

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+from math import sqrt
+from ridger import generate_ridge_image, IMSIZE
+
+
+def height_map(x, y):
+    dist = sqrt((x - 500) ** 2 + (y - 500) ** 2)
+    # donut hole
+    if dist < 100:
+        return 0
+    # outside the donut
+    if dist > 300:
+        return 0
+    return 50
+
+
+def line_color(x1, y1, x2, y2):
+    if y1 == y2:
+        return (255, 255, 255, 255)
+    elif y1 < y2:
+        return (255, 0, 0, 255)
+    else:
+        return (0, 255, 0, 255)
+
+
+def data_to_screen(x, y) -> tuple[int, int]:
+    # how long is the far away side?
+    horizon_min_side = 600
+    horizon_max_side = 1000
+    # how long is here?
+    this_horizon = (
+        horizon_min_side + (horizon_max_side - horizon_min_side) * y / IMSIZE[1]
+    )
+    # scale x to the current hporizon keeping the center
+    x = IMSIZE[0] / 2 + (x - IMSIZE[0] / 2) * this_horizon / horizon_max_side
+    return x, y
+
+
+generate_ridge_image(
+    height_map, line_color, bgcolor=(128, 128, 128, 255), data_to_screen=data_to_screen
+).show()