intial commit

dithermaker.py

+import math
+import numpy as np
+import cv2
+import argparse
+import os
+
+
+def parse_arguments():
+    usage_text = (
+        "Converts an image into a dithered svg file."
+    )
+    parser = argparse.ArgumentParser(description=usage_text)
+    parser.add_argument("-i", "--input", type=str,
+                        help="Input filename.")
+    parser.add_argument("-o", "--output", type=str, default="",
+                        help="Output filename (default: <filename_in>_dither.svg).")
+    parser.add_argument("--invert", action="store_true",
+                        help="Output white dots on a black background.")
+    parser.add_argument("-n", "--number", type=int, default=100,
+                        help="Number of dots horizontally (default=100).")
+    parser.add_argument("-a", type=float, default=0.1,
+                        help="small diameter 0-1 (default:0.1).")
+    parser.add_argument("-b", type=float, default=0.82,
+                        help="large diameter 0-1 (default:0.82).")
+    return parser.parse_known_args()
+
+
+def int_constrain(a, a_min, a_max):
+    return np.clip(a.astype(np.int32), a_min, a_max)
+
+
+def rescale(a, a_min, a_max):
+    a_min_obs = np.min(a)
+    a_max_obs = np.max(a)
+
+    a_norm = (a - a_min_obs) / (a_max_obs - a_min_obs)
+    return a_min + a_norm * (a_max - a_min)
+
+
+def write_svg(filename, x, y, r, invert=False):
+    x_max = int(np.max(x))
+    y_max = int(np.max(y))
+    with open(filename, "w") as f:
+
+        if invert:
+            col_back = "black"
+            col_front = "white"
+        else:
+            col_back = "white"
+            col_front = "black"
+        f.write(f'<svg width="{x_max}" height="{y_max}" '
+                f'xmlns="http://www.w3.org/2000/svg" '
+                f'style="background-color:{col_back}">\n')
+
+        for xi, yi, ri in zip(x, y, r):
+            f.write(f'\t<circle cx="{xi:.2f}" cy="{yi:.2f}" r="{ri:.2f}" fill="{col_front}"/>\n')
+
+        f.write('</svg>\n')
+
+
+def main():
+    args, _ = parse_arguments()
+
+    filename_in = args.input
+
+    if args.output == "":
+        filename_out = os.path.splitext(filename_in)[0] + f"_dither.svg"
+    else:
+        filename_out = args.output
+
+    img = cv2.imread(filename_in, cv2.IMREAD_UNCHANGED)
+    if len(img.shape) == 3:
+        img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+
+    f = math.sqrt(3) / 2
+    h, w = img.shape
+    n_x = args.number
+    n_y = int((1/f) * n_x * h / w)
+
+    d_x = w / n_x
+    d_y = d_x * f
+
+    img_blur = cv2.blur(img, (int(d_x), int(d_x)))
+
+    x = d_x * np.arange(n_x)
+    y = d_y * np.arange(n_y)
+
+    xx, yy = np.meshgrid(x, y)
+
+    xx[1::2, :] += d_x / 2
+
+    xx_f = xx.flatten()
+    yy_f = yy.flatten()
+
+    xx_f_samp = int_constrain(xx.flatten(), 0, w - 1)
+    yy_f_samp = int_constrain(yy.flatten(), 0, h - 1)
+
+    r_max = args.a*d_x/2
+    r_min = args.b*d_x/2
+    r_f = rescale(img_blur[yy_f_samp, xx_f_samp], r_min, r_max)
+
+    write_svg(filename_out, xx_f, yy_f, r_f, invert=args.invert)
+
+
+if __name__ == "__main__":
+    main()

requirements.txt

+numpy>=1.1
+opencv-contrib-python>=4.1