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validate and analyze dimensions of [PNG, JPG, GIF], image files in Python.
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#!/usr/bin/env python | |
# | |
# Corey Goldberg, 2013 | |
# | |
# Python 2.7 | |
"""validate and analyze dimensions of image files. Supports: PNG, JPG, GIF.""" | |
import StringIO | |
import struct | |
def is_gif(data): | |
return (data[:6] in ('GIF87a', 'GIF89a')) | |
def is_png(data): | |
return ((data[:8] == '\211PNG\r\n\032\n') and (data[12:16] == 'IHDR')) | |
def is_old_png(data): | |
return ((data[:8] == '\211PNG\r\n\032\n') and (data[12:16] != 'IHDR')) | |
def is_jpeg(data): | |
return (data[:2] == '\377\330') | |
def get_image_dimensions(data): | |
if len(data) < 16: | |
raise Exception('not valid image data') | |
elif is_gif(data): | |
w, h = struct.unpack('<HH', data[6:10]) | |
width = int(w) | |
height = int(h) | |
elif is_png(data): | |
w, h = struct.unpack('>LL', data[16:24]) | |
width = int(w) | |
height = int(h) | |
elif is_old_png(data): | |
w, h = struct.unpack('>LL', data[8:16]) | |
width = int(w) | |
height = int(h) | |
elif is_jpeg(data): | |
jpeg = StringIO.StringIO(data) | |
jpeg.read(2) | |
b = jpeg.read(1) | |
try: | |
while (b and ord(b) != 0xDA): | |
while (ord(b) != 0xFF): b = jpeg.read(1) | |
while (ord(b) == 0xFF): b = jpeg.read(1) | |
if (ord(b) >= 0xC0 and ord(b) <= 0xC3): | |
jpeg.read(3) | |
h, w = struct.unpack('>HH', jpeg.read(4)) | |
break | |
else: | |
jpeg.read(int(struct.unpack('>H', jpeg.read(2))[0])-2) | |
b = jpeg.read(1) | |
width = int(w) | |
height = int(h) | |
except struct.error: | |
pass | |
except ValueError: | |
pass | |
else: | |
raise Exception('not valid image data') | |
return width, height | |
if __name__ == '__main__': | |
with open('foo.png', 'rb') as f: | |
data = f.read() | |
w, h = get_image_dimensions(data) | |
print w, h | |
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