[utils] Add decode_png for openload (#9706)

This commit is contained in:
Yen Chi Hsuan 2016-08-07 02:42:58 +08:00
parent ad152e2d95
commit d3f8e038fe
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@ -47,6 +47,7 @@ from .compat import (
compat_socket_create_connection,
compat_str,
compat_struct_pack,
compat_struct_unpack,
compat_urllib_error,
compat_urllib_parse,
compat_urllib_parse_urlencode,
@ -2969,3 +2970,110 @@ def parse_m3u8_attributes(attrib):
def urshift(val, n):
return val >> n if val >= 0 else (val + 0x100000000) >> n
# Based on png2str() written by @gdkchan and improved by @yokrysty
# Originally posted at https://github.com/rg3/youtube-dl/issues/9706
def decode_png(png_data):
# Reference: https://www.w3.org/TR/PNG/
header = png_data[8:]
if png_data[:8] != b'\x89PNG\x0d\x0a\x1a\x0a' or header[4:8] != b'IHDR':
raise IOError('Not a valid PNG file.')
int_map = {1: '>B', 2: '>H', 4: '>I'}
unpack_integer = lambda x: compat_struct_unpack(int_map[len(x)], x)[0]
chunks = []
while header:
length = unpack_integer(header[:4])
header = header[4:]
chunk_type = header[:4]
header = header[4:]
chunk_data = header[:length]
header = header[length:]
header = header[4:] # Skip CRC
chunks.append({
'type': chunk_type,
'length': length,
'data': chunk_data
})
ihdr = chunks[0]['data']
width = unpack_integer(ihdr[:4])
height = unpack_integer(ihdr[4:8])
idat = b''
for chunk in chunks:
if chunk['type'] == b'IDAT':
idat += chunk['data']
if not idat:
raise IOError('Unable to read PNG data.')
decompressed_data = bytearray(zlib.decompress(idat))
stride = width * 3
pixels = []
def _get_pixel(idx):
x = idx % stride
y = idx // stride
return pixels[y][x]
for y in range(height):
basePos = y * (1 + stride)
filter_type = decompressed_data[basePos]
current_row = []
pixels.append(current_row)
for x in range(stride):
color = decompressed_data[1 + basePos + x]
basex = y * stride + x
left = 0
up = 0
if x > 2:
left = _get_pixel(basex - 3)
if y > 0:
up = _get_pixel(basex - stride)
if filter_type == 1: # Sub
color = (color + left) & 0xff
elif filter_type == 2: # Up
color = (color + up) & 0xff
elif filter_type == 3: # Average
color = (color + ((left + up) >> 1)) & 0xff
elif filter_type == 4: # Paeth
a = left
b = up
c = 0
if x > 2 and y > 0:
c = _get_pixel(basex - stride - 3)
p = a + b - c
pa = abs(p - a)
pb = abs(p - b)
pc = abs(p - c)
if pa <= pb and pa <= pc:
color = (color + a) & 0xff
elif pb <= pc:
color = (color + b) & 0xff
else:
color = (color + c) & 0xff
current_row.append(color)
return width, height, pixels