PIL & image size reduction script

[Philippe Martin]

Hi,

Thanks to the NG, I got the script hereunder working.

1) I am not certain that the call to convert does much (checking the doc)
2) Can this be improved as far as the final image size in (X,Y) ?


For instance, passing a large .jpg with a target byte size of 7000, I get
final (X,Y) results around (213, 174) ... but might want to strech it a bit
while keeping the byte size.

Thanks,

Philippe





#*******************************************************************************
def Image_Reduce(self, p_filename, p_size):
BASE_SIZE = 400.0
l_im = Image.open(p_filename)

l_size = l_im.size

if l_size[0] > l_size[1]:
l_ratio = BASE_SIZE / l_size[0]
l_x_size = l_ratio * l_size[0]
l_y_size = l_ratio * l_size[1]
else:
l_ratio = BASE_SIZE / l_size[1]
l_x_size = l_ratio * l_size[0]
l_y_size = l_ratio * l_size[1]


# l_im.show()
l_image = l_im.resize( (l_x_size, l_y_size))
l_image = l_image.convert(mode="RGB", palette=Image.ADAPTIVE)

l_done = False

l_tmp_file_name = 'sc_tmp_file.jpg'

while False == l_done:
l_image.save(l_tmp_file_name)
l_st = os.stat(l_tmp_file_name)
print 'HERE ', l_st
if p_size < l_st[6]:

l_ratio -= 0.005
print 'NEW RATIO = ', l_ratio
l_x_size = l_ratio * l_size[0]
l_y_size = l_ratio * l_size[1]
l_image = l_im.resize( (l_x_size, l_y_size))



else:
l_done = True


l_image.show()
print l_image.size

 

[nikie]

Hi,

Thanks to the NG, I got the script hereunder working.

1) I am not certain that the call to convert does much (checking the doc)

I think you only need it if your source image comes in a format that
can't be stored into a jpeg file (e.g. 8-bit paletted). You'll need
that if you're converting from GIF files, for example. It shouldn't
hurt otherwise.

2) Can this be improved as far as the final image size in (X,Y) ?

I'm not sure if I get you: You tell the image object it's new
(X,Y)-size in the resize method, don't you?

For instance, passing a large .jpg with a target byte size of 7000, I get
final (X,Y) results around (213, 174) ... but might want to strech it a bit
while keeping the byte size.

If I got you right, you want to compress the image to a certain file
size. Maybe you should try optimizing the additional save parameters
for the jpeg encoder.
(http://www.pythonware.com/library/pil/handbook/formats.htm). Try
reducing the "quality" parameter.
l_image.save(l_tmp_file_name, quality=25)

Hope this helps.

Niki

 

[Philippe Martin]

I think you only need it if your source image comes in a format that
can't be stored into a jpeg file (e.g. 8-bit paletted). You'll need
that if you're converting from GIF files, for example. It shouldn't
hurt otherwise.

OK

I'm not sure if I get you: You tell the image object it's new
(X,Y)-size in the resize method, don't you?

Yes, I keep reducing the (X,Y) size as long as the file is too large (in
bytes)

If I got you right, you want to compress the image to a certain file
size. Maybe you should try optimizing the additional save parameters
for the jpeg encoder.
(http://www.pythonware.com/library/pil/handbook/formats.htm). Try
reducing the "quality" parameter.
l_image.save(l_tmp_file_name, quality=25)

That might be it !!!

Thanks,

Philippe

 

[Philippe Martin]

PS: where can I find those extra parameters in the doc (ex: quality) ... I
must be blind.

Philippe

 

[nikie]

PS: where can I find those extra parameters in the doc (ex: quality) ... I
must be blind.

In the http://www.pythonware.com/library/pil/handbook/formats.htm page.
Look in the "JPEG" section. Different file formats support different
options.

 

[Philippe Martin]

Many thanks

In the http://www.pythonware.com/library/pil/handbook/formats.htm page.
Look in the "JPEG" section. Different file formats support different
options.