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parameters for Image.fromstring function in pil

P: 3
i need to do is modify the image in memory like resizing the image in memory etc ... with out saving it disk as i have to return back the image with out saving it disk
PIL supports the use of StringIO objects being passed in place of file
objects. StringIO objects are binary strings of variable length that are kept
in memory so i saved the image in stringio objects the following code does that

for gif image
import Image
import StringIO
im = Image.open("/home/bharath/Desktop/photos/lena.gif")
fil=StringIO.StringIO()
im.save(fil,"GIF")
cached_image=fil.getvalue()

or

for jpeg image
import Image
import StringIO
im = Image.open("/home/bharath/Desktop/photos/lena.jpg")
fil=StringIO.StringIO()
im.save(fil,"JPEG")
cached_image=fil.getvalue()

but i can't apply resize operation on cached_image as it a str object
but i found out that Image.formstring(mode, size, data, decoder, parameters) Creates an image memory from pixel data in a string so i did the following

for gif image
ima=Image.fromstring('P',(128,128),cached_image,'g if')
imr=ima.resize((64,64),Image.ANTIALIAS)
imr.save("/home/bharath/Desktop/photos/resize_lena3.gif","GIF")

i am getting the following error

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/bharath/Desktop/image.py", line 8, in <module>
ima=Image.fromstring('P',(128,128),cached_image,'g if')
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 1744, in fromstring
im.fromstring(data, decoder_name, args)
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 577, in fromstring
raise ValueError("cannot decode image data")
ValueError: cannot decode image data

for jpeg image
ma=Image.fromstring('P',(128,128),cached_image,'jp eg')
imr=ima.resize((64,64),Image.ANTIALIAS)
imr.save("/home/bharath/Desktop/photos/resize_lena3.gif","JPEG")

i am getting the following error ...

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/bharath/Desktop/image.py", line 8, in <module>
ima=Image.fromstring('RGB',(128,128),cached_image, 'jpeg')
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 1744, in fromstring
im.fromstring(data, decoder_name, args)
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 570, in fromstring
d = _getdecoder(self.mode, decoder_name, args)
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 373, in _getdecoder
return apply(decoder, (mode,) + args + extra)
TypeError: function takes at least 3 arguments (1 given)

but if i remove the 4th parameter that is decoder_name i.e 'gif' or 'jpeg' in function Image.formstring(mode, size, data, decoder, parameters) there is no error(when decoder_name is not given it defaults to raw image type) .. image even gets resized and gets saved but that image is distorted image that shows that it is not decoded in correct way .. and when i want a image to be decoded according to a format i.e gif or jpeg i think i need to pass a extra parameter in the function Image.fromstring(mode, size, data, decoder, parameters) along with a decoder name to be decoded correctly .

pls can u tell what extra parameters i have to pass with an example (taking my example itself )
Reply

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Feb 14 '08 #1
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1 Reply


P: 1
I'm not sure what to pass in for the fromstring module. But you can do something like this to save a JPEG image from string buffer:

newImage = Image.fromstring('L', (325, 256), cached_image_string)
newImage.save(filename, "JPEG")


i need to do is modify the image in memory like resizing the image in memory etc ... with out saving it disk as i have to return back the image with out saving it disk
PIL supports the use of StringIO objects being passed in place of file
objects. StringIO objects are binary strings of variable length that are kept
in memory so i saved the image in stringio objects the following code does that

for gif image
import Image
import StringIO
im = Image.open("/home/bharath/Desktop/photos/lena.gif")
fil=StringIO.StringIO()
im.save(fil,"GIF")
cached_image=fil.getvalue()

or

for jpeg image
import Image
import StringIO
im = Image.open("/home/bharath/Desktop/photos/lena.jpg")
fil=StringIO.StringIO()
im.save(fil,"JPEG")
cached_image=fil.getvalue()

but i can't apply resize operation on cached_image as it a str object
but i found out that Image.formstring(mode, size, data, decoder, parameters) Creates an image memory from pixel data in a string so i did the following

for gif image
ima=Image.fromstring('P',(128,128),cached_image,'g if')
imr=ima.resize((64,64),Image.ANTIALIAS)
imr.save("/home/bharath/Desktop/photos/resize_lena3.gif","GIF")

i am getting the following error

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/bharath/Desktop/image.py", line 8, in <module>
ima=Image.fromstring('P',(128,128),cached_image,'g if')
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 1744, in fromstring
im.fromstring(data, decoder_name, args)
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 577, in fromstring
raise ValueError("cannot decode image data")
ValueError: cannot decode image data

for jpeg image
ma=Image.fromstring('P',(128,128),cached_image,'jp eg')
imr=ima.resize((64,64),Image.ANTIALIAS)
imr.save("/home/bharath/Desktop/photos/resize_lena3.gif","JPEG")

i am getting the following error ...

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/bharath/Desktop/image.py", line 8, in <module>
ima=Image.fromstring('RGB',(128,128),cached_image, 'jpeg')
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 1744, in fromstring
im.fromstring(data, decoder_name, args)
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 570, in fromstring
d = _getdecoder(self.mode, decoder_name, args)
File "/usr/lib/python2.5/site-packages/PIL/Image.py", line 373, in _getdecoder
return apply(decoder, (mode,) + args + extra)
TypeError: function takes at least 3 arguments (1 given)

but if i remove the 4th parameter that is decoder_name i.e 'gif' or 'jpeg' in function Image.formstring(mode, size, data, decoder, parameters) there is no error(when decoder_name is not given it defaults to raw image type) .. image even gets resized and gets saved but that image is distorted image that shows that it is not decoded in correct way .. and when i want a image to be decoded according to a format i.e gif or jpeg i think i need to pass a extra parameter in the function Image.fromstring(mode, size, data, decoder, parameters) along with a decoder name to be decoded correctly .

pls can u tell what extra parameters i have to pass with an example (taking my example itself )
Reply

Forward
Mar 10 '08 #2

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