[Image-SIG] What is the best way to anti-alias a very large resolution image in PIL

Andrew Wilson andrewwilson at alum.mit.edu
Tue Sep 13 18:24:56 CEST 2011

I've had similar problems with PIL, you may want to take a look at OpenCV it
can open rather large images and resize them.

On Thu, Sep 8, 2011 at 7:07 AM, Craig Coleman (C) <
Craig.Coleman at ordnancesurvey.co.uk> wrote:

> **
> Hi,
> I have a really thorny problem.
> I need to downsample a raster map that is 23622x23622 pixels to 7874x7874
> pixels using the ANTIALIAS filter.
> I have the following Python code:
> >>> import Image
> >>> img = Image.open(r"C:\temp\24bit_nd.tif")
> >>> nimg = img.resize((7874,7874),Image.ANTIALIAS)
> As soon as the resize method is called, python crashes instantly.  I
> presume this is a memory allocation issue.
> Is there another way of performing anti-aliasing on such a large image (its
> 2.7GB uncompressed although I'm using LZW for storage).
> I have tried converting the file to 8bit with a palette and this
> successfully downsamples but the ANTIALIAS is not performed.  What am I
> doing wrong?
> *Craig Coleman*
> *Technical Lead
> Information Systems, Ordnance Survey
> L0F2, Adanac Drive, SOUTHAMPTON, United Kingdom, SO16 0AS
> Phone: +44 (0) 2380 054641
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> craig.coleman at ordnancesurvey.co.uk*
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