diff options
| -rw-r--r-- | youtube_dl/utils.py | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py index 97ddd9883..ddbfcd2f1 100644 --- a/youtube_dl/utils.py +++ b/youtube_dl/utils.py @@ -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 |