a42a9ca543
Null values in the signature data will cause the compute box calculation to fail. Filter them out during json.loads
53 lines
1.5 KiB
Python
53 lines
1.5 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
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AA = 5 # super sampling gor 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 {'x': list(filter(None, pt['x'])), 'y': list(filter(None, pt['y']))}
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if type(data) is str:
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drawing = json.loads(data, object_hook=_remove_empty_pts)
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elif type(data) is 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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width = int(round(max(chain(*[d['x'] for d in drawing])))) + 10
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height = int(round(max(chain(*[d['y'] for d in drawing])))) + 10
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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 line in drawing:
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len_line = len(line['x'])
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points = [(line['x'][i]*AA, line['y'][i]*AA)
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for i in range(0, len_line)]
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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((width, height), Image.ANTIALIAS)
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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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