mk_piano_image.py

# -*- coding: utf-8 -*-
import math
from PIL import Image, ImageDraw, ImageFont


#
# see details: https://en.wikipedia.org/wiki/MIDI_tuning_standard
#
_KTAB = [
    "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"
    ]

def _nn2scale(nn):
    return _KTAB[int(nn) % 12], int(nn / 12) - 1

def _ok2nn(k, oct):
    return (oct + 1) * 12 + _KTAB.index(k)

def _nn2freq(nn):
    return math.pow(2, (nn - 69) / 12.) * 440

#def _freq2nn(f):
#    return 69 + 12 * math.log(f / 440., 2)

def _img_hstack(img_l, img_r):
    newimg = Image.new("RGB", (img_l.width + img_r.width, img_l.height))
    newimg.paste(img_l, box=(0, 0, img_l.width, img_l.height))
    newimg.paste(img_r, box=(img_l.width, 0, img_r.width + img_l.width, img_r.height))
    return newimg


if __name__ == '__main__':
    # ticks from A0(21) to C8(108)
    ticks_info = []
    for nn in range(21, 109):
        k, oct = _nn2scale(nn)
        freq = _nn2freq(nn)
        ticks_info.append(
            (k, oct, nn, freq))

    #
    fnt = ImageFont.truetype('msgothic.ttc', 80)
    result = None
    imh = 120
    for i in range(len(ticks_info) - 1):
        k, oct, nn, freq = ticks_info[i]
        w = 30
        if k.endswith("#"):
            w *= 2
        img = Image.new("RGB", (w, imh), "#ffffff")
        dctx = ImageDraw.Draw(img)
        dctx.line([
                (0, 0), (w, 0),
                ], fill="#000000", width=10)
        dctx.line([
                (0, imh), (w, imh),
                ], fill="#000000", width=10)
        if k.endswith("#"):
            dctx.rectangle([
                    (0, 0),
                    (w / 2, imh / 3 * 2),
                    ], fill="#000000", outline="#222222")
        else:
            txt = k
            txtsz = dctx.textsize(txt, fnt)
            dctx.text(
                ((img.width - txtsz[0]) / 2, img.height - txtsz[1] - 20),
                txt,
                font=fnt,
                fill="#4444ff"
                )
            if k == "C":
                txt = "%d" % oct
                txtsz = dctx.textsize(txt, fnt)
                dctx.text(
                    ((img.width - txtsz[0]) / 2, img.height - txtsz[1] - 60),
                    txt,
                    font=fnt,
                    fill="#ff4444"
                    )
        del dctx
        if result is None:
            result = img
        else:
            result = _img_hstack(result, img)
    result = result.resize((1920, result.height))
    result.save("myaxis.png")