/usr/lib/python3/dist-packages/pyavm/embed.py is in python3-pyavm 0.9.2-3.
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import warnings
from .jpeg import is_jpeg, JPEGFile, JPEGSegment
from .png import is_png, PNGFile, PNGChunk
def embed_xmp(image_in, image_out, xmp_packet):
if is_jpeg(image_in):
# Check length
if len(xmp_packet) >= 65503:
raise Exception("XMP packet is too long to embed in JPG file")
# XMP segment
xmp_segment = JPEGSegment()
# APP1 marker
xmp_segment.bytes = b"\xff\xe1"
# Length of XMP packet + 2 + 29
xmp_segment.bytes += struct.pack('>H', len(xmp_packet) + 29 + 2)
# XMP Namespace URI (NULL-terminated)
xmp_segment.bytes += b"http://ns.adobe.com/xap/1.0/\x00"
# XMP packet
xmp_segment.bytes += xmp_packet
# Read in input file
jpeg_file = JPEGFile.read(image_in)
# Check if there is already XMP data in the file
existing = []
for segment in jpeg_file.segments:
if segment.type == 'APP1':
if segment.bytes[4:32] == b'http://ns.adobe.com/xap/1.0/':
existing.append(segment)
if existing:
warnings.warn("Discarding existing XMP packet from JPEG file")
for e in existing:
jpeg_file.segments.remove(e)
# Position at which to insert the packet
markers = [x.type for x in jpeg_file.segments]
if 'APP1' in markers: # Put it after existing APP1
index = markers.index('APP1') + 1
elif 'APP0' in markers: # Put it after existing APP0
index = markers.index('APP0') + 1
elif 'SOF' in markers:
index = markers.index('SOF')
else:
raise ValueError("Could not find SOF marker")
# Insert segment into JPEG file
jpeg_file.segments.insert(index, xmp_segment)
jpeg_file.write(image_out)
elif is_png(image_in):
xmp_chunk = PNGChunk()
# Keyword
xmp_chunk.data = b'XML:com.adobe.xmp'
# Null separator
xmp_chunk.data += b'\x00'
# Compression flag
xmp_chunk.data += b'\x00'
# Compression method
xmp_chunk.data += b'\x00'
# Null separator
xmp_chunk.data += b'\x00'
# Null separator
xmp_chunk.data += b'\x00'
# Text
xmp_chunk.data += xmp_packet
# Set type
xmp_chunk.type = b'iTXt'
# Read in input file
png_file = PNGFile.read(image_in)
# Check if there is already XMP data in the file
existing = []
for chunk in png_file.chunks:
if chunk.type == b'iTXt':
if chunk.data.startswith(b'XML:com.adobe.xmp'):
existing.append(chunk)
if existing:
warnings.warn("Discarding existing XMP packet from PNG file")
for e in existing:
png_file.chunks.remove(e)
# Insert chunk into PNG file
png_file.chunks.insert(1, xmp_chunk)
png_file.write(image_out)
else:
raise Exception("Only JPG and PNG files are supported at this time")
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