epub converter: add rgb2closest_color.py

src/util/rgb2closest_color.py

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+from webcolors import html4_hex_to_names, hex_to_rgb
+
+# 16 основных цветов, hex соответвуют hex цветам livecarta
+# названия другие
+html4_hex_to_names = {'#00ffff': 'aqua', '#000000': 'black', '#0000ff': 'blue', '#ff00ff': 'fuchsia',
+                      '#008000': 'green', '#808080': 'grey', '#00ff00': 'lime', '#800000': 'maroon', '#000080': 'navy',
+                      '#808000': 'olive', '#800080': 'purple', '#ff0000': 'red', '#c0c0c0': 'silver', '#008080': 'teal',
+                      '#ffffff': 'white', '#ffff00': 'yellow'}
+
+
+def rgb2hsv(r, g, b):
+    r /= 255
+    g /= 255
+    b /= 255
+    max_c = max(r, g, b)
+    min_c = min(r, g, b)
+    value = max_c
+    if min_c == max_c:
+        return 0.0, 0.0, value * 100
+
+    saturation = (max_c - min_c) / max_c
+    rc = (max_c - r) / (max_c - min_c)
+    gc = (max_c - g) / (max_c - min_c)
+    bc = (max_c - b) / (max_c - min_c)
+
+    if r == max_c:
+        hue = 0.0 + bc - gc
+    elif g == max_c:
+        hue = 2.0 + rc - bc
+    else:
+        hue = 4.0 + gc - rc
+
+    hue0 = (hue / 6.0) % 1.0
+    hue2 = ((hue + 6) / 6.0) if (hue < 0) else (hue / 6.0)
+
+    return hue2 * 360, saturation * 100, value * 100
+
+
+HTML_COLORS_HSV = {}
+for key, name in html4_hex_to_names.items():
+    r, g, b = hex_to_rgb(key)
+    h, s, v = rgb2hsv(r, g, b)
+    HTML_COLORS_HSV[name] = (h, s, v)
+
+
+def rgb2closest_html_color_name(color):
+    """
+
+
+    - get color in hsv (hue, saturation, value)
+    - try to match with black, grey, silver (black, darkGray, lightGray) as this colors matches badly even in hsv model
+
+    - calc hue difference between color and all base colors
+    - if for new base color hue diff same as for any other, try to measure saturation and value
+    (it happens for similar colors like red - pink, blue - dark blue)
+
+    :param color:  str, color in hex
+    :return: base color name that matches best to a given color
+    """
+
+    if color == (255, 255, 255):
+        return 'white'
+
+    diff2base_color_dict = {}
+    rgb = hex_to_rgb(color)
+    hue_request, s_request, v_request = rgb2hsv(*rgb)
+    if v_request <= 30:
+        return 'black'
+    if v_request <= 50 and s_request <= 25:  # **
+        return 'gray'
+    if s_request <= 10 and (90 <= v_request <= 100):
+        return 'white'
+    if s_request <= 40:
+        return 'silver'
+
+    for _, name in html4_hex_to_names.items():
+        if name in ['white', 'black', 'grey', 'silver']:
+            continue
+        hue_html, s_html, v_html = HTML_COLORS_HSV[name]
+
+        hue_diff = abs(hue_html - hue_request)
+
+        if hue_diff == 20:
+            pass
+
+        if hue_diff in diff2base_color_dict:
+            dist_cur_color = (s_request - s_html) ** 2 + (v_request - v_html) ** 2
+            hue_prev, s_prev, v_prev = HTML_COLORS_HSV[diff2base_color_dict[hue_diff]]
+            dist_prev_color = (s_request - s_prev) ** 2 + (v_request - v_prev) ** 2
+            # print(name, diff2base_color_dict[hue_diff],)
+            # print(dist_cur_color,  dist_prev_color)
+            # print()
+            if dist_cur_color < dist_prev_color:
+                diff2base_color_dict[hue_diff] = name
+        else:
+            diff2base_color_dict[hue_diff] = name
+
+    # print(diff2base_color_dict)
+    return diff2base_color_dict[min(diff2base_color_dict.keys())]
+
+
+if __name__ == '__main__':
+
+    hex_colors = [
+        #'#945893',
+        # '#96F',
+        # '#000', # black
+        # '#4C4C4C', # black
+        # '#A00',
+        # '#99F',
+        '#f89921',
+
+        # '#f89921', '#EFF8F6'
+        # '#e5c099',  # yellow
+        # '#008b90',  # teal
+        # '#c4762a',  # red
+        # '#996A95',  '#70416F', # purple
+        # '#D5C9D3', '#E9E2E8',  # silver
+        # '#FFD472', '#F47B4D', '#FFFBEF', '#F47B4D', # yellow, red ,yellow, red
+        # '#B0DFD7', '#EFF8F6', '#5CC4B7'
+    ]
+
+    for c in hex_colors:
+        n = rgb2closest_html_color_name(c)
+        print(n) # "Actual colour:", c, ", closest colour name:",
+        # print()