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Merge pull request #10 from crucifyml/master
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add functions to get size from memory buffer
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@scardine
scardine authored Jan 8, 2019
2 parents 5bf2d5f + 1aad2e8 commit fb25377
Showing 1 changed file with 198 additions and 148 deletions.
346 changes: 198 additions & 148 deletions get_image_size.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
import collections
import json
import os
import io
import struct

FILE_UNKNOWN = "Sorry, don't know how to get size for this file."
Expand Down Expand Up @@ -72,6 +73,19 @@ def get_image_size(file_path):
return (img.width, img.height)


def get_image_size_from_bytesio(input, size):
"""
Return (width, height) for a given img file content - no external
dependencies except the os and struct builtin modules
Args:
input (io.IOBase): io object support read & seek
size (int): size of buffer in byte
"""
img = get_image_metadata_from_bytesio(input, size)
return (img.width, img.height)


def get_image_metadata(file_path):
"""
Return an `Image` object for a given img file content - no external
Expand All @@ -86,156 +100,172 @@ def get_image_metadata(file_path):
size = os.path.getsize(file_path)

# be explicit with open arguments - we need binary mode
with open(file_path, "rb") as input:
height = -1
width = -1
data = input.read(26)
msg = " raised while trying to decode as JPEG."

if (size >= 10) and data[:6] in (b'GIF87a', b'GIF89a'):
# GIFs
imgtype = GIF
w, h = struct.unpack("<HH", data[6:10])
with io.open(file_path, "rb") as input:
return get_image_metadata_from_bytesio(input, size, file_path)


def get_image_metadata_from_bytesio(input, size, file_path=None):
"""
Return an `Image` object for a given img file content - no external
dependencies except the os and struct builtin modules
Args:
input (io.IOBase): io object support read & seek
size (int): size of buffer in byte
file_path (str): path to an image file
Returns:
Image: (path, type, file_size, width, height)
"""
height = -1
width = -1
data = input.read(26)
msg = " raised while trying to decode as JPEG."

if (size >= 10) and data[:6] in (b'GIF87a', b'GIF89a'):
# GIFs
imgtype = GIF
w, h = struct.unpack("<HH", data[6:10])
width = int(w)
height = int(h)
elif ((size >= 24) and data.startswith(b'\211PNG\r\n\032\n')
and (data[12:16] == b'IHDR')):
# PNGs
imgtype = PNG
w, h = struct.unpack(">LL", data[16:24])
width = int(w)
height = int(h)
elif (size >= 16) and data.startswith(b'\211PNG\r\n\032\n'):
# older PNGs
imgtype = PNG
w, h = struct.unpack(">LL", data[8:16])
width = int(w)
height = int(h)
elif (size >= 2) and data.startswith(b'\377\330'):
# JPEG
imgtype = JPEG
input.seek(0)
input.read(2)
b = input.read(1)
try:
while (b and ord(b) != 0xDA):
while (ord(b) != 0xFF):
b = input.read(1)
while (ord(b) == 0xFF):
b = input.read(1)
if (ord(b) >= 0xC0 and ord(b) <= 0xC3):
input.read(3)
h, w = struct.unpack(">HH", input.read(4))
break
else:
input.read(
int(struct.unpack(">H", input.read(2))[0]) - 2)
b = input.read(1)
width = int(w)
height = int(h)
elif ((size >= 24) and data.startswith(b'\211PNG\r\n\032\n')
and (data[12:16] == b'IHDR')):
# PNGs
imgtype = PNG
w, h = struct.unpack(">LL", data[16:24])
except struct.error:
raise UnknownImageFormat("StructError" + msg)
except ValueError:
raise UnknownImageFormat("ValueError" + msg)
except Exception as e:
raise UnknownImageFormat(e.__class__.__name__ + msg)
elif (size >= 26) and data.startswith(b'BM'):
# BMP
imgtype = 'BMP'
headersize = struct.unpack("<I", data[14:18])[0]
if headersize == 12:
w, h = struct.unpack("<HH", data[18:22])
width = int(w)
height = int(h)
elif (size >= 16) and data.startswith(b'\211PNG\r\n\032\n'):
# older PNGs
imgtype = PNG
w, h = struct.unpack(">LL", data[8:16])
elif headersize >= 40:
w, h = struct.unpack("<ii", data[18:26])
width = int(w)
height = int(h)
elif (size >= 2) and data.startswith(b'\377\330'):
# JPEG
imgtype = JPEG
input.seek(0)
input.read(2)
b = input.read(1)
try:
while (b and ord(b) != 0xDA):
while (ord(b) != 0xFF):
b = input.read(1)
while (ord(b) == 0xFF):
b = input.read(1)
if (ord(b) >= 0xC0 and ord(b) <= 0xC3):
input.read(3)
h, w = struct.unpack(">HH", input.read(4))
break
else:
input.read(
int(struct.unpack(">H", input.read(2))[0]) - 2)
b = input.read(1)
width = int(w)
height = int(h)
except struct.error:
raise UnknownImageFormat("StructError" + msg)
except ValueError:
raise UnknownImageFormat("ValueError" + msg)
except Exception as e:
raise UnknownImageFormat(e.__class__.__name__ + msg)
elif (size >= 26) and data.startswith(b'BM'):
# BMP
imgtype = 'BMP'
headersize = struct.unpack("<I", data[14:18])[0]
if headersize == 12:
w, h = struct.unpack("<HH", data[18:22])
width = int(w)
height = int(h)
elif headersize >= 40:
w, h = struct.unpack("<ii", data[18:26])
width = int(w)
# as h is negative when stored upside down
height = abs(int(h))
else:
raise UnknownImageFormat(
"Unkown DIB header size:" +
str(headersize))
elif (size >= 8) and data[:4] in (b"II\052\000", b"MM\000\052"):
# Standard TIFF, big- or little-endian
# BigTIFF and other different but TIFF-like formats are not
# supported currently
imgtype = TIFF
byteOrder = data[:2]
boChar = ">" if byteOrder == "MM" else "<"
# maps TIFF type id to size (in bytes)
# and python format char for struct
tiffTypes = {
1: (1, boChar + "B"), # BYTE
2: (1, boChar + "c"), # ASCII
3: (2, boChar + "H"), # SHORT
4: (4, boChar + "L"), # LONG
5: (8, boChar + "LL"), # RATIONAL
6: (1, boChar + "b"), # SBYTE
7: (1, boChar + "c"), # UNDEFINED
8: (2, boChar + "h"), # SSHORT
9: (4, boChar + "l"), # SLONG
10: (8, boChar + "ll"), # SRATIONAL
11: (4, boChar + "f"), # FLOAT
12: (8, boChar + "d") # DOUBLE
}
ifdOffset = struct.unpack(boChar + "L", data[4:8])[0]
try:
countSize = 2
input.seek(ifdOffset)
ec = input.read(countSize)
ifdEntryCount = struct.unpack(boChar + "H", ec)[0]
# 2 bytes: TagId + 2 bytes: type + 4 bytes: count of values + 4
# bytes: value offset
ifdEntrySize = 12
for i in range(ifdEntryCount):
entryOffset = ifdOffset + countSize + i * ifdEntrySize
input.seek(entryOffset)
tag = input.read(2)
tag = struct.unpack(boChar + "H", tag)[0]
if(tag == 256 or tag == 257):
# if type indicates that value fits into 4 bytes, value
# offset is not an offset but value itself
type = input.read(2)
type = struct.unpack(boChar + "H", type)[0]
if type not in tiffTypes:
raise UnknownImageFormat(
"Unkown TIFF field type:" +
str(type))
typeSize = tiffTypes[type][0]
typeChar = tiffTypes[type][1]
input.seek(entryOffset + 8)
value = input.read(typeSize)
value = int(struct.unpack(typeChar, value)[0])
if tag == 256:
width = value
else:
height = value
if width > -1 and height > -1:
break
except Exception as e:
raise UnknownImageFormat(str(e))
elif size >= 2:
# see http://en.wikipedia.org/wiki/ICO_(file_format)
imgtype = 'ICO'
input.seek(0)
reserved = input.read(2)
if 0 != struct.unpack("<H", reserved)[0]:
raise UnknownImageFormat(FILE_UNKNOWN)
format = input.read(2)
assert 1 == struct.unpack("<H", format)[0]
num = input.read(2)
num = struct.unpack("<H", num)[0]
if num > 1:
import warnings
warnings.warn("ICO File contains more than one image")
# http://msdn.microsoft.com/en-us/library/ms997538.aspx
w = input.read(1)
h = input.read(1)
width = ord(w)
height = ord(h)
# as h is negative when stored upside down
height = abs(int(h))
else:
raise UnknownImageFormat(
"Unkown DIB header size:" +
str(headersize))
elif (size >= 8) and data[:4] in (b"II\052\000", b"MM\000\052"):
# Standard TIFF, big- or little-endian
# BigTIFF and other different but TIFF-like formats are not
# supported currently
imgtype = TIFF
byteOrder = data[:2]
boChar = ">" if byteOrder == "MM" else "<"
# maps TIFF type id to size (in bytes)
# and python format char for struct
tiffTypes = {
1: (1, boChar + "B"), # BYTE
2: (1, boChar + "c"), # ASCII
3: (2, boChar + "H"), # SHORT
4: (4, boChar + "L"), # LONG
5: (8, boChar + "LL"), # RATIONAL
6: (1, boChar + "b"), # SBYTE
7: (1, boChar + "c"), # UNDEFINED
8: (2, boChar + "h"), # SSHORT
9: (4, boChar + "l"), # SLONG
10: (8, boChar + "ll"), # SRATIONAL
11: (4, boChar + "f"), # FLOAT
12: (8, boChar + "d") # DOUBLE
}
ifdOffset = struct.unpack(boChar + "L", data[4:8])[0]
try:
countSize = 2
input.seek(ifdOffset)
ec = input.read(countSize)
ifdEntryCount = struct.unpack(boChar + "H", ec)[0]
# 2 bytes: TagId + 2 bytes: type + 4 bytes: count of values + 4
# bytes: value offset
ifdEntrySize = 12
for i in range(ifdEntryCount):
entryOffset = ifdOffset + countSize + i * ifdEntrySize
input.seek(entryOffset)
tag = input.read(2)
tag = struct.unpack(boChar + "H", tag)[0]
if(tag == 256 or tag == 257):
# if type indicates that value fits into 4 bytes, value
# offset is not an offset but value itself
type = input.read(2)
type = struct.unpack(boChar + "H", type)[0]
if type not in tiffTypes:
raise UnknownImageFormat(
"Unkown TIFF field type:" +
str(type))
typeSize = tiffTypes[type][0]
typeChar = tiffTypes[type][1]
input.seek(entryOffset + 8)
value = input.read(typeSize)
value = int(struct.unpack(typeChar, value)[0])
if tag == 256:
width = value
else:
height = value
if width > -1 and height > -1:
break
except Exception as e:
raise UnknownImageFormat(str(e))
elif size >= 2:
# see http://en.wikipedia.org/wiki/ICO_(file_format)
imgtype = 'ICO'
input.seek(0)
reserved = input.read(2)
if 0 != struct.unpack("<H", reserved)[0]:
raise UnknownImageFormat(FILE_UNKNOWN)
format = input.read(2)
assert 1 == struct.unpack("<H", format)[0]
num = input.read(2)
num = struct.unpack("<H", num)[0]
if num > 1:
import warnings
warnings.warn("ICO File contains more than one image")
# http://msdn.microsoft.com/en-us/library/ms997538.aspx
w = input.read(1)
h = input.read(1)
width = ord(w)
height = ord(h)
else:
raise UnknownImageFormat(FILE_UNKNOWN)

return Image(path=file_path,
type=imgtype,
Expand All @@ -258,15 +288,35 @@ class Test_get_image_size(unittest.TestCase):
def setUp(self):
pass

def test_get_image_size_from_bytesio(self):
img = self.data[0]
p = img['path']
with io.open(p, 'rb') as fp:
b = fp.read()
fp = io.BytesIO(b)
sz = len(b)
output = get_image_size_from_bytesio(fp, sz)
self.assertTrue(output)
self.assertEqual(output,
(img['width'],
img['height']))

def test_get_image_metadata_from_bytesio(self):
img = self.data[0]
p = img['path']
with io.open(p, 'rb') as fp:
b = fp.read()
fp = io.BytesIO(b)
sz = len(b)
output = get_image_metadata_from_bytesio(fp, sz)
self.assertTrue(output)
for field in image_fields:
self.assertEqual(getattr(output, field), None if field == 'path' else img[field])

def test_get_image_metadata(self):
img = self.data[0]
output = get_image_metadata(img['path'])
self.assertTrue(output)
self.assertEqual(output.path, img['path'])
self.assertEqual(output.width, img['width'])
self.assertEqual(output.height, img['height'])
self.assertEqual(output.type, img['type'])
self.assertEqual(output.file_size, img['file_size'])
for field in image_fields:
self.assertEqual(getattr(output, field), img[field])

Expand Down

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