[Image-SIG] generating images of different sizes

[Rajorshi Biswas]

Thanks a lot Larry. That indeed does help! You see,
I have a strange type of requirement wherein I have to
generate image files of a particular resolution having
as large a file size as possible.
 Initially I was trying this by getting a high quality 
jpeg or bmp file, and converting this *without* any
options to PIL's Image.save. I was only partly successful.
For instance, I need a 352x288 jpeg of 300-350 KB size,
but I am about 200 KB short. Then I tried a different
approach - creating an image in PIL from scratch and
using ImageDraw's methods to go on adding lines, points 
etc until the filesize came close to what I wanted. But 
I found the size saturating at a point (far less than
the filesize I wanted though).
 Is there a better way of doing what I want ?

Thanks for the help mate!
Rajorshi


On Wed, 21 Jul 2004 13:57:13 -0500
"Larry Bates" <lbates at syscononline.com> wrote:

> Since PIL cannot (at the current time) support compressed
> TIFF images, you cannot reduce their size by any options
> from within PIL.  When I need to produce compressed TIFF
> images, I use external program like tiffcp to handle the
> compression (of course I do it by calling it from within
> my Python program via os.system() call).
> 
> I normally look into the source code for each different 
> PIL plug-in to see what options are available.  The files
> will be in the format ???ImagePlugin.py and are normally
> located in /lib/site-packages/PIL subdirectory.
> 
> Below is a snippet of code that shows the keywords for
> JPEG plug-in:
> 
>     # get keyword arguments
>     im.encoderconfig = (
>         im.encoderinfo.get("quality", 0),
>         im.encoderinfo.has_key("progressive"),
>         im.encoderinfo.get("smooth", 0),
>         im.encoderinfo.has_key("optimize"),
>         im.encoderinfo.get("streamtype", 0),
>         dpi[0], dpi[1]
>         )
> 
> This means he understands quality, progessive, smooth,
> optimize, and streamtype keywords.  The only one I've
> ever actually used it quality.
> 
> HTH, Larry Bates
> 
> 
> -----Original Message-----
> From: Rajorshi Biswas [mailto:rajorshi at alumnux.com]
> Sent: Tuesday, July 20, 2004 6:19 AM
> To: image-sig at python.org
> Subject: [Image-SIG] generating images of different sizes
> 
> 
> Hi,
>  This is my first post to the image-sig mailing list, so
> hello to you all.
>  My knowledge of different file formats is somewhat limited.
> What I have to do is essentially this : Given a resolution
> (such as 352x288) and a file-size (such as 300KB), I have
> to generate images using PIL of the following formats:
> [ jpeg, gif, wbmp, bmp, png, tiff ]. 
>  I have achieved the first part, that is I can, starting
> from a jpg image, generate all the other types with any
> resolution (by resizing and using PIL's Image.save). But
> I have no control over file size.
>  To do that I found that there's a variant of the Image.save
> method that takes in a third parameter:
> Image.save( filename, format, options ).
>  The PIL manual says that 
> "Keyword options can be used to provide additional 
> instructions to the writer. If a writer doesn't recognise 
> an option, it is silently ignored. The available options 
> are described later in this handbook."
>  Could someone please tell me what these options are ?
> I seem to be unable to find the 'options' in the manual.
> If it is not there, could someone tell me,
> 
> 1] What i need to do to reduce the size of the tiff files
> I generate, what options I need to add to the call
> Image.save('a.tiff') .
> 
> 2] Same for bmp files.
>  
>  That's a lot of queries for the first post! Please help!
> 
> Thanks.
> Rajorshi
> 
> 
> 
> 
> 
> 


-- 
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Rajorshi Biswas

Trainee, Alumnus Software Ltd.
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