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