import struct
_UNIT_KM = -3
_UNIT_100M = -2
_UNIT_10M = -1
_UNIT_1M = 0
_UNIT_10CM = 1
_UNIT_CM = 2
_UNIT_MM = 3
_UNIT_0_1MM = 4
_UNIT_0_01MM = 5
_UNIT_UM = 6
_UNIT_INCH = 6
def _convertToDPI(density, unit):
if unit == _UNIT_KM:
return int(density * 0.0000254 + 0.5)
elif unit == _UNIT_100M:
return int(density * 0.000254 + 0.5)
elif unit == _UNIT_10M:
return int(density * 0.00254 + 0.5)
elif unit == _UNIT_1M:
return int(density * 0.0254 + 0.5)
elif unit == _UNIT_10CM:
return int(density * 0.254 + 0.5)
elif unit == _UNIT_CM:
return int(density * 2.54 + 0.5)
elif unit == _UNIT_MM:
return int(density * 25.4 + 0.5)
elif unit == _UNIT_0_1MM:
return density * 254
elif unit == _UNIT_0_01MM:
return density * 2540
elif unit == _UNIT_UM:
return density * 25400
return density
def get(filepath):
"""
Return (width, height) for a given img file content
no requirements
"""
height = -1
width = -1
with open(filepath, 'rb') as fhandle:
head = fhandle.read(24)
size = len(head)
# handle GIFs
if size >= 10 and head[:6] in (b'GIF87a', b'GIF89a'):
# Check to see if content_type is correct
try:
width, height = struct.unpack("<hh", head[6:10])
except struct.error:
raise ValueError("Invalid GIF file")
# see png edition spec bytes are below chunk length then and finally the
elif size >= 24 and head.startswith(b'\211PNG\r\n\032\n') and head[12:16] == b'IHDR':
try:
width, height = struct.unpack(">LL", head[16:24])
except struct.error:
raise ValueError("Invalid PNG file")
# Maybe this is for an older PNG version.
elif size >= 16 and head.startswith(b'\211PNG\r\n\032\n'):
# Check to see if we have the right content type
try:
width, height = struct.unpack(">LL", head[8:16])
except struct.error:
raise ValueError("Invalid PNG file")
# handle JPEGs
elif size >= 2 and head.startswith(b'\377\330'):
try:
fhandle.seek(0) # Read 0xff next
size = 2
ftype = 0
while not 0xc0 <= ftype <= 0xcf or ftype in [0xc4, 0xc8, 0xcc]:
fhandle.seek(size, 1)
byte = fhandle.read(1)
while ord(byte) == 0xff:
byte = fhandle.read(1)
ftype = ord(byte)
size = struct.unpack('>H', fhandle.read(2))[0] - 2
# We are at a SOFn block
fhandle.seek(1, 1) # Skip `precision' byte.
height, width = struct.unpack('>HH', fhandle.read(4))
except struct.error:
raise ValueError("Invalid JPEG file")
# handle JPEG2000s
elif size >= 12 and head.startswith(b'\x00\x00\x00\x0cjP \r\n\x87\n'):
fhandle.seek(48)
try:
height, width = struct.unpack('>LL', fhandle.read(8))
except struct.error:
raise ValueError("Invalid JPEG2000 file")
return width, height
def getDPI(filepath):
"""
Return (width, height) for a given img file content
no requirements
"""
xDPI = -1
yDPI = -1
with open(filepath, 'rb') as fhandle:
head = fhandle.read(24)
size = len(head)
# handle GIFs
# GIFs doesn't have density
if size >= 10 and head[:6] in (b'GIF87a', b'GIF89a'):
pass
# see png edition spec bytes are below chunk length then and finally the
elif size >= 24 and head.startswith(b'\211PNG\r\n\032\n'):
chunkOffset = 8
chunk = head[8:]
while True:
chunkType = chunk[4:8]
if chunkType == b'pHYs':
try:
xDensity, yDensity, unit = struct.unpack(">LLB", chunk[8:])
except struct.error:
raise ValueError("Invalid PNG file")
if unit:
xDPI = _convertToDPI(xDensity, _UNIT_1M)
yDPI = _convertToDPI(yDensity, _UNIT_1M)
else: # no unit
xDPI = xDensity
yDPI = yDensity
break
elif chunkType == b'IDAT':
break
else:
try:
dataSize, = struct.unpack(">L", chunk[0:4])
except struct.error:
raise ValueError("Invalid PNG file")
chunkOffset += dataSize + 12
fhandle.seek(chunkOffset)
chunk = fhandle.read(17)
# handle JPEGs
elif size >= 2 and head.startswith(b'\377\330'):
try:
fhandle.seek(0) # Read 0xff next
size = 2
ftype = 0
while not 0xc0 <= ftype <= 0xcf:
if ftype == 0xe0: # APP0 marker
fhandle.seek(7, 1)
unit, xDensity, yDensity = struct.unpack(">BHH", fhandle.read(5))
if unit == 1 or unit == 0:
xDPI = xDensity
yDPI = yDensity
elif unit == 2:
xDPI = _convertToDPI(xDensity, _UNIT_CM)
yDPI = _convertToDPI(yDensity, _UNIT_CM)
break
fhandle.seek(size, 1)
byte = fhandle.read(1)
while ord(byte) == 0xff:
byte = fhandle.read(1)
ftype = ord(byte)
size = struct.unpack('>H', fhandle.read(2))[0] - 2
except struct.error:
raise ValueError("Invalid JPEG file")
# handle JPEG2000s
elif size >= 12 and head.startswith(b'\x00\x00\x00\x0cjP \r\n\x87\n'):
fhandle.seek(32)
# skip JP2 image header box
headerSize = struct.unpack('>L', fhandle.read(4))[0] - 8
fhandle.seek(4, 1)
foundResBox = False
try:
while headerSize > 0:
print("headerSize", headerSize)
boxHeader = fhandle.read(8)
boxType = boxHeader[4:]
print(boxType)
if boxType == 'res ': # find resolution super box
foundResBox = True
headerSize -= 8
print("found res super box")
break
print("@1", boxHeader)
boxSize, = struct.unpack('>L', boxHeader[:4])
print("boxSize", boxSize)
fhandle.seek(boxSize - 8, 1)
headerSize -= boxSize
if foundResBox:
while headerSize > 0:
boxHeader = fhandle.read(8)
boxType = boxHeader[4:]
print(boxType)
if boxType == 'resd': # Display resolution box
print("@2")
yDensity, xDensity, yUnit, xUnit = struct.unpack(">HHBB", fhandle.read(10))
xDPI = _convertToDPI(xDensity, xUnit)
yDPI = _convertToDPI(yDensity, yUnit)
break
boxSize, = struct.unpack('>L', boxHeader[:4])
print("boxSize", boxSize)
fhandle.seek(boxSize - 8, 1)
headerSize -= boxSize
except struct.error as e:
print(e)
raise ValueError("Invalid JPEG2000 file")
return xDPI, yDPI