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utility: refactor get_image_properties() into utility.py
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@jmcnamara
jmcnamara committed Feb 17, 2024
1 parent 55e8534 commit b049981
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357 changes: 261 additions & 96 deletions xlsxwriter/utility.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,109 +5,33 @@
# SPDX-License-Identifier: BSD-2-Clause
# Copyright 2013-2023, John McNamara, jmcnamara@cpan.org
#
import re
import datetime
import hashlib
import os
import re
from struct import unpack
from warnings import warn
from .exceptions import UndefinedImageSize
from .exceptions import UnsupportedImageFormat

COL_NAMES = {}

# fmt: off
CHAR_WIDTHS = {
" ": 3,
"!": 5,
'"': 6,
"#": 7,
"$": 7,
"%": 11,
"&": 10,
"'": 3,
"(": 5,
")": 5,
"*": 7,
"+": 7,
",": 4,
"-": 5,
".": 4,
"/": 6,
"0": 7,
"1": 7,
"2": 7,
"3": 7,
"4": 7,
"5": 7,
"6": 7,
"7": 7,
"8": 7,
"9": 7,
":": 4,
";": 4,
"<": 7,
"=": 7,
">": 7,
"?": 7,
"@": 13,
"A": 9,
"B": 8,
"C": 8,
"D": 9,
"E": 7,
"F": 7,
"G": 9,
"H": 9,
"I": 4,
"J": 5,
"K": 8,
"L": 6,
"M": 12,
"N": 10,
"O": 10,
"P": 8,
"Q": 10,
"R": 8,
"S": 7,
"T": 7,
"U": 9,
"V": 9,
"W": 13,
"X": 8,
"Y": 7,
"Z": 7,
"[": 5,
"\\": 6,
"]": 5,
"^": 7,
"_": 7,
"`": 4,
"a": 7,
"b": 8,
"c": 6,
"d": 8,
"e": 8,
"f": 5,
"g": 7,
"h": 8,
"i": 4,
"j": 4,
"k": 7,
"l": 4,
"m": 12,
"n": 8,
"o": 8,
"p": 8,
"q": 8,
"r": 5,
"s": 6,
"t": 5,
"u": 8,
"v": 7,
"w": 11,
"x": 7,
"y": 7,
"z": 6,
"{": 5,
"|": 7,
"}": 5,
"~": 7,
" ": 3, "!": 5, '"': 6, "#": 7, "$": 7, "%": 11, "&": 10, "'": 3,
"(": 5, ")": 5, "*": 7, "+": 7, ",": 4, "-": 5, ".": 4, "/": 6,
"0": 7, "1": 7, "2": 7, "3": 7, "4": 7, "5": 7, "6": 7, "7": 7,
"8": 7, "9": 7, ":": 4, ";": 4, "<": 7, "=": 7, ">": 7, "?": 7,
"@": 13, "A": 9, "B": 8, "C": 8, "D": 9, "E": 7, "F": 7, "G": 9,
"H": 9, "I": 4, "J": 5, "K": 8, "L": 6, "M": 12, "N": 10, "O": 10,
"P": 8, "Q": 10, "R": 8, "S": 7, "T": 7, "U": 9, "V": 9, "W": 13,
"X": 8, "Y": 7, "Z": 7, "[": 5, "\\": 6, "]": 5, "^": 7, "_": 7,
"`": 4, "a": 7, "b": 8, "c": 6, "d": 8, "e": 8, "f": 5, "g": 7,
"h": 8, "i": 4, "j": 4, "k": 7, "l": 4, "m": 12, "n": 8, "o": 8,
"p": 8, "q": 8, "r": 5, "s": 6, "t": 5, "u": 8, "v": 7, "w": 11,
"x": 7, "y": 7, "z": 6, "{": 5, "|": 7, "}": 5, "~": 7,
}
# fmt: on

# Compile performance critical regular expressions.
re_leading = re.compile(r"^\s")
Expand Down Expand Up @@ -873,3 +797,244 @@ def preserve_whitespace(string):
return True
else:
return False


def get_image_properties(filename, image_data):
# Extract dimension information from the image file.
height = 0
width = 0
x_dpi = 96
y_dpi = 96

if not image_data:
# Open the image file and read in the data.
fh = open(filename, "rb")
data = fh.read()
else:
# Read the image data from the user supplied byte stream.
data = image_data.getvalue()

digest = hashlib.sha256(data).hexdigest()

# Get the image filename without the path.
image_name = os.path.basename(filename)

# Look for some common image file markers.
marker1 = unpack("3s", data[1:4])[0]
marker2 = unpack(">H", data[:2])[0]
marker3 = unpack("2s", data[:2])[0]
marker4 = unpack("<L", data[:4])[0]
marker5 = (unpack("4s", data[40:44]))[0]
marker6 = unpack("4s", data[:4])[0]

png_marker = b"PNG"
bmp_marker = b"BM"
emf_marker = b" EMF"
gif_marker = b"GIF8"

if marker1 == png_marker:
(image_type, width, height, x_dpi, y_dpi) = _process_png(data)

elif marker2 == 0xFFD8:
(image_type, width, height, x_dpi, y_dpi) = _process_jpg(data)

elif marker3 == bmp_marker:
(image_type, width, height) = _process_bmp(data)

elif marker4 == 0x9AC6CDD7:
(image_type, width, height, x_dpi, y_dpi) = _process_wmf(data)

elif marker4 == 1 and marker5 == emf_marker:
(image_type, width, height, x_dpi, y_dpi) = _process_emf(data)

elif marker6 == gif_marker:
(image_type, width, height, x_dpi, y_dpi) = _process_gif(data)

else:
raise UnsupportedImageFormat(
"%s: Unknown or unsupported image file format." % filename
)

# Check that we found the required data.
if not height or not width:
raise UndefinedImageSize("%s: no size data found in image file." % filename)

if not image_data:
fh.close()

# Set a default dpi for images with 0 dpi.
if x_dpi == 0:
x_dpi = 96
if y_dpi == 0:
y_dpi = 96

return image_type, width, height, image_name, x_dpi, y_dpi, digest


def _process_png(data):
# Extract width and height information from a PNG file.
offset = 8
data_length = len(data)
end_marker = False
width = 0
height = 0
x_dpi = 96
y_dpi = 96

# Search through the image data to read the height and width in the
# IHDR element. Also read the DPI in the pHYs element.
while not end_marker and offset < data_length:
length = unpack(">I", data[offset + 0 : offset + 4])[0]
marker = unpack("4s", data[offset + 4 : offset + 8])[0]

# Read the image dimensions.
if marker == b"IHDR":
width = unpack(">I", data[offset + 8 : offset + 12])[0]
height = unpack(">I", data[offset + 12 : offset + 16])[0]

# Read the image DPI.
if marker == b"pHYs":
x_density = unpack(">I", data[offset + 8 : offset + 12])[0]
y_density = unpack(">I", data[offset + 12 : offset + 16])[0]
units = unpack("b", data[offset + 16 : offset + 17])[0]

if units == 1:
x_dpi = x_density * 0.0254
y_dpi = y_density * 0.0254

if marker == b"IEND":
end_marker = True
continue

offset = offset + length + 12

return "png", width, height, x_dpi, y_dpi


def _process_jpg(data):
# Extract width and height information from a JPEG file.
offset = 2
data_length = len(data)
end_marker = False
width = 0
height = 0
x_dpi = 96
y_dpi = 96

# Search through the image data to read the JPEG markers.
while not end_marker and offset < data_length:
marker = unpack(">H", data[offset + 0 : offset + 2])[0]
length = unpack(">H", data[offset + 2 : offset + 4])[0]

# Read the height and width in the 0xFFCn elements (except C4, C8
# and CC which aren't SOF markers).
if (
(marker & 0xFFF0) == 0xFFC0
and marker != 0xFFC4
and marker != 0xFFC8
and marker != 0xFFCC
):
height = unpack(">H", data[offset + 5 : offset + 7])[0]
width = unpack(">H", data[offset + 7 : offset + 9])[0]

# Read the DPI in the 0xFFE0 element.
if marker == 0xFFE0:
units = unpack("b", data[offset + 11 : offset + 12])[0]
x_density = unpack(">H", data[offset + 12 : offset + 14])[0]
y_density = unpack(">H", data[offset + 14 : offset + 16])[0]

if units == 1:
x_dpi = x_density
y_dpi = y_density

if units == 2:
x_dpi = x_density * 2.54
y_dpi = y_density * 2.54

# Workaround for incorrect dpi.
if x_dpi == 1:
x_dpi = 96
if y_dpi == 1:
y_dpi = 96

if marker == 0xFFDA:
end_marker = True
continue

offset = offset + length + 2

return "jpeg", width, height, x_dpi, y_dpi


def _process_gif(data):
# Extract width and height information from a GIF file.
x_dpi = 96
y_dpi = 96

width = unpack("<h", data[6:8])[0]
height = unpack("<h", data[8:10])[0]

return "gif", width, height, x_dpi, y_dpi


def _process_bmp(data):
# Extract width and height information from a BMP file.
width = unpack("<L", data[18:22])[0]
height = unpack("<L", data[22:26])[0]
return "bmp", width, height


def _process_wmf(data):
# Extract width and height information from a WMF file.
x_dpi = 96
y_dpi = 96

# Read the bounding box, measured in logical units.
x1 = unpack("<h", data[6:8])[0]
y1 = unpack("<h", data[8:10])[0]
x2 = unpack("<h", data[10:12])[0]
y2 = unpack("<h", data[12:14])[0]

# Read the number of logical units per inch. Used to scale the image.
inch = unpack("<H", data[14:16])[0]

# Convert to rendered height and width.
width = float((x2 - x1) * x_dpi) / inch
height = float((y2 - y1) * y_dpi) / inch

return "wmf", width, height, x_dpi, y_dpi


def _process_emf(data):
# Extract width and height information from a EMF file.

# Read the bounding box, measured in logical units.
bound_x1 = unpack("<l", data[8:12])[0]
bound_y1 = unpack("<l", data[12:16])[0]
bound_x2 = unpack("<l", data[16:20])[0]
bound_y2 = unpack("<l", data[20:24])[0]

# Convert the bounds to width and height.
width = bound_x2 - bound_x1
height = bound_y2 - bound_y1

# Read the rectangular frame in units of 0.01mm.
frame_x1 = unpack("<l", data[24:28])[0]
frame_y1 = unpack("<l", data[28:32])[0]
frame_x2 = unpack("<l", data[32:36])[0]
frame_y2 = unpack("<l", data[36:40])[0]

# Convert the frame bounds to mm width and height.
width_mm = 0.01 * (frame_x2 - frame_x1)
height_mm = 0.01 * (frame_y2 - frame_y1)

# Get the dpi based on the logical size.
x_dpi = width * 25.4 / width_mm
y_dpi = height * 25.4 / height_mm

# This is to match Excel's calculation. It is probably to account for
# the fact that the bounding box is inclusive-inclusive. Or a bug.
width += 1
height += 1

return "emf", width, height, x_dpi, y_dpi
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