apng

apng(animated portable network graphics) is png with chunks added in order acTL, fcTL, fdAT.
'89 50 4e 47 0d 0a 1a 0a'(hex) > IHDRchunk > other chunks > IENDchunk

chunk

name
IHDR
PLTE
acTL
fcTL
IDAT
fcTL
fdAT
IEND
length
00 00 00 0d
4bytes
00 00 00 08
00 00 00 1a
4bytes
00 00 00 1a
4bytes
00 00 00 00
type
49 48 44 52
50 4c 54 45
61 63 54 4c
66 63 54 4c
49 44 41 54
66 63 54 4c
66 64 41 54
49 45 4e 44
data
13bytes
?
8bytes
26bytes
?
26bytes
(4+n)bytes
0byte
crc
4bytes
4bytes
4bytes
4bytes
4bytes
4bytes
4bytes
ae 42 60 82
color_type = 03
default = frame1

IHDR

data

width(4)
height(4)
bit_depth(1)
color_type(1)
compression_method(1)
filter_method(1)
interlace_method(1)
grayscale
01,02,04,08,10
00
rgb
08,10
02
PLTE
01,02,04,08
03
grayscale
(alpha)
08,10
04
rgb
(alpha)
08,10
06

PLTE

data

palette(1)
...

acTL(apng)

data

num_frames(4)
num_plays(4)

fcTL(apng)

data

sequence_number(4)
width(4)
height(4)
x_offset(4)
y_offset(4)
delay_num(2)
delay_den(2)
dispose_op(1)
blend_op(1)

fdAT(apng)

data

sequence_number(4)
frame_data(?)