There is an errors embed album art with mutagen?

Question

The problem is, whenever i embed a picture into the mp3 and that mp3 file always increase less bytes than the picture actually is. I'll explain in code:

import os
from mutagen.mp3 import MP3
from mutagen.id3 import ID3, APIC, error
from mutagen import File

audio = ID3()
with open('111.mp3', 'rb') as f:
    rawfile = f.read()

for dirpath, dirnames, filenames in os.walk('E:/Exp/apic'):
    for fname in filenames:
        path = os.path.join(dirpath, fname)

        ap = APIC(
            encoding = 3,
            mime = 'image/jpg',
            type = 3,
            desc = u'Cover',
            data = open(path, 'rb').read() )

        sz_changed = os.stat('111.mp3').st_size
        audio.add(ap)
        audio.save('111.mp3')
        sz_changed = os.stat('111.mp3').st_size - sz_changed
        print u'Lost bytes：%d' % (len(ap.data)-sz_changed)
        with open('111.mp3', 'wb') as f:
            f.write(rawfile) #reset

the code shows that i can't embed the whole picture into that mp3 and neight my mp3 player nor my phone can read the broken art so what exactly the problem is? although i can successfully embed a pic only when i previously embed a much more larger pic.

now i am going to show the result of the above code:

Lost bytes：4174
Lost bytes：5594
Lost bytes：4924
Lost bytes：4777
Lost bytes：4938
Lost bytes：4750
Lost bytes：5558
Lost bytes：4710
Lost bytes：4924
Lost bytes：5686
Lost bytes：4936
Lost bytes：4788
Lost bytes：5319
Lost bytes：5605
Lost bytes：4790
Lost bytes：4781
Lost bytes：5692
Lost bytes：5248

Answer 1

Try changing:

mime = 'image/jpg' to 'image/jpeg'

I had a similar problem before and that helped