84 lines
2.6 KiB
Python
84 lines
2.6 KiB
Python
"""
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Very inspired by zivezab's django-autograph
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https://github.com/zivezab/django-autograph/blob/master/autograph/utils.py
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"""
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import json
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from itertools import chain
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from PIL import Image, ImageDraw, ImageOps, __version__ as PIL_VERSION
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AA = 5 # super sampling for antialiasing
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def draw_signature(data, as_file=False):
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"""Draw signature based on lines stored in json_string.
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`data` can be a json object (list in fact) or a json string
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if `as_file` is True, a temp file is returned instead of Image instance
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"""
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def _remove_empty_pts(pt):
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return {
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"x": list(filter(lambda n: n is not None, pt["x"])),
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"y": list(filter(lambda n: n is not None, pt["y"])),
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}
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if isinstance(data, str):
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drawing = json.loads(data, object_hook=_remove_empty_pts)
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elif isinstance(data, list):
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drawing = data
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else:
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raise ValueError
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# Compute box
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padding = 10
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min_width = int(round(min(chain(*[d["x"] for d in drawing])))) - padding
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max_width = int(round(max(chain(*[d["x"] for d in drawing])))) + padding
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width = max_width - min_width
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min_height = int(round(min(chain(*[d["y"] for d in drawing])))) - padding
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max_height = int(round(max(chain(*[d["y"] for d in drawing])))) + padding
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height = max_height - min_height
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# Draw image
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im = Image.new("RGBA", (width * AA, height * AA))
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draw = ImageDraw.Draw(im)
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for coords in drawing:
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line_length = len(coords["x"])
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if line_length == 1:
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# This is a single point, convert to a circle of 2x2 AA pixels
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draw.ellipse(
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[
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(
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(coords["x"][0] - min_width) * AA,
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(coords["y"][0] - min_height) * AA,
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),
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(
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(coords["x"][0] - min_width + 2) * AA,
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(coords["y"][0] - min_height + 2) * AA,
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),
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],
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fill="#000",
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)
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else:
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points = [
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((coords["x"][i] - min_width) * AA, (coords["y"][i] - min_height) * AA)
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for i in range(0, line_length)
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]
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draw.line(points, fill="#000", width=2 * AA)
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im = ImageOps.expand(im)
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# Smart crop
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bbox = im.getbbox()
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if bbox:
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im.crop(bbox)
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im.thumbnail(
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(width, height),
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# Image.ANTIALIAS is replaced in PIL 10.0.0
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Image.ANTIALIAS if int(PIL_VERSION.split(".")[0]) < 10 else Image.LANCZOS,
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)
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if as_file:
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ret = im._dump(format="PNG")
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else:
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ret = im
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return ret
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