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Add support for transparent PNGs

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This commit is contained in:
Andy Roberts 2017-01-27 17:19:21 +00:00
parent 673f7b5bc4
commit eea3f7ad6c
3 changed files with 28 additions and 5 deletions
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22
stegano/lsb/lsb.py
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@ -44,7 +44,8 @@ def hide(input_image_file, message, auto_convert_rgb=False):
assert message_length != 0, "message length is zero" assert message_length != 0, "message length is zero"
img = Image.open(input_image_file) img = Image.open(input_image_file)
if img.mode != 'RGB':
if img.mode not in ['RGB', 'RGBA']:
if not auto_convert_rgb: if not auto_convert_rgb:
print('The mode of the image is not RGB. Mode is {}'.\ print('The mode of the image is not RGB. Mode is {}'.\
format(img.mode)) format(img.mode))
@ -71,7 +72,10 @@ def hide(input_image_file, message, auto_convert_rgb=False):
if index + 3 <= len_message_bits : if index + 3 <= len_message_bits :
# Get the colour component. # Get the colour component.
(r, g, b) = img.getpixel((col, row)) pixel = img.getpixel((col, row))
r = pixel[0]
g = pixel[1]
b = pixel[2]
# Change the Least Significant Bit of each colour component. # Change the Least Significant Bit of each colour component.
r = tools.setlsb(r, message_bits[index]) r = tools.setlsb(r, message_bits[index])
@ -79,7 +83,12 @@ def hide(input_image_file, message, auto_convert_rgb=False):
b = tools.setlsb(b, message_bits[index+2]) b = tools.setlsb(b, message_bits[index+2])
# Save the new pixel # Save the new pixel
encoded.putpixel((col, row), (r, g , b)) if img.mode == 'RGBA':
updated_pixel = (r, g, b, pixel[3])
else:
updated_pixel = (r, g, b)
encoded.putpixel((col, row), updated_pixel)
index += 3 index += 3
else: else:
@ -102,8 +111,11 @@ def reveal(input_image_file):
for row in range(height): for row in range(height):
for col in range(width): for col in range(width):
# color = [r, g, b] # pixel = [r, g, b] or [r,g,b,a]
for color in img.getpixel((col, row)): pixel = img.getpixel((col, row))
if img.mode == 'RGBA':
pixel = pixel[:3] # ignore the alpha
for color in pixel:
buff += (color&1)<<(7-count) buff += (color&1)<<(7-count)
count += 1 count += 1
if count == 8: if count == 8:

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tests/sample-files/transparent.png Normal file
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11
tests/test_lsb.py
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@ -49,6 +49,17 @@ class TestLSB(unittest.TestCase):
self.assertEqual(message, clear_message) self.assertEqual(message, clear_message)
def test_with_transparent_png(self):
messages_to_hide = ["a", "foo", "Hello World!", ":Python:"]
for message in messages_to_hide:
secret = lsb.hide("./tests/sample-files/transparent.png", message)
secret.save("./image.png")
clear_message = lsb.reveal("./image.png")
self.assertEqual(message, clear_message)
def test_with_text_file(self): def test_with_text_file(self):
text_file_to_hide = "./tests/sample-files/lorem_ipsum.txt" text_file_to_hide = "./tests/sample-files/lorem_ipsum.txt"
with open(text_file_to_hide) as f: with open(text_file_to_hide) as f: