1#!/usr/bin/env python
2
3import base64
4import os
5import secrets
6import subprocess
7import sys
8import tempfile
9
10from flask import Flask, flash, redirect, render_template, request
11import wcag_contrast_ratio as contrast
12
13
14app = Flask(__name__)
15app.secret_key = secrets.token_hex()
16
17
18VERSION = subprocess.check_output(["dominant_colours", "--version"]).decode("utf8")
19
20
21@app.route("/")
22def index():
23    return render_template("index.html", version=VERSION)
24
25
26@app.template_filter("usable_colours")
27def usable_colours(colours):
28    result = []
29
30    for hex_string in colours:
31        r = red(hex_string)
32        g = green(hex_string)
33        b = blue(hex_string)
34
35        ratio = contrast.rgb((r / 255, g / 255, b / 255), (1, 1, 1))
36
37        if contrast.passes_AA(ratio):
38            result.append(hex_string)
39
40    return result
41
42
43@app.template_filter("red")
44def red(hex_string):
45    return int(hex_string[1:3], 16)
46
47
48@app.template_filter("green")
49def green(hex_string):
50    return int(hex_string[3:5], 16)
51
52
53@app.template_filter("blue")
54def blue(hex_string):
55    return int(hex_string[5:7], 16)
56
57
58@app.route("/palette", methods=["GET", "POST"])
59def get_palette():
60    if request.method == "GET":
61        return redirect("/")
62
63    if request.method == "POST":
64        uploaded_file = request.files["file"]
65        _, extension = os.path.splitext(uploaded_file.filename)
66
67        with tempfile.NamedTemporaryFile(suffix=extension) as tmp_file:
68            uploaded_file.save(tmp_file)
69
70            # If we don't flush here, the file may be incomplete.  This can
71            # lead to errors like:
72            #
73            #     failed to fill whole buffer
74            #
75            # when running dominant_colours.
76            tmp_file.flush()
77
78            proc = subprocess.Popen(
79                ["dominant_colours", tmp_file.name, "--no-palette", "--max-colours=5"],
80                stdout=subprocess.PIPE,
81                stderr=subprocess.PIPE,
82            )
83            stdout, stderr = proc.communicate()
84            return_code = proc.poll()
85
86            if return_code != 0:
87                stderr = stderr.decode(sys.stdin.encoding)
88                flash(f"Something went wrong:<br/>{stderr}")
89                return redirect("/")
90
91            stdout = stdout.decode(sys.stdin.encoding)
92            colours = stdout.strip().split("\n")
93
94            with tempfile.NamedTemporaryFile(suffix="jpg") as thumbnail_file:
95                subprocess.check_call(
96                    [
97                        "convert",
98                        tmp_file.name,
99                        "-resize",
100                        "600x600",
101                        thumbnail_file.name,
102                    ]
103                )
104                thumbnail_file.seek(0)
105                thumbnail = thumbnail_file.read()
106
107            thumbnail_data_uri = (
108                b"data:image/jpg;base64," + base64.b64encode(thumbnail)
109            ).decode("ascii")
110
111            return render_template(
112                "palette.html",
113                colours=colours,
114                thumbnail_data_uri=thumbnail_data_uri,
115                version=VERSION,
116            )
117
118
119if __name__ == "__main__":
120    app.run(debug=True, host="0.0.0.0", port=4711)