[Image-SIG] Upsample an image

[Fredrik Lundh]

Fredrik Lundh wrote:

>> When I tried downsample an image using im.resize and then upsampled it to 
>> get to the original size, it looked a bit blurry and lost a lot of details.
> 
> that's expected: if you downsample an image, you lose information.  once 
> lost, there's no way to get it back.

footnote: if you're e.g. implementing an image display tool, the right 
solution is to keep resampling/transforming from the same source image:

      original = Image.open(...)

      # (re)draw
      display_im = original.resize(display_size)
      render_to_screen(display_im)

instead of resizing the same image over and over again:

      image = Image.open(...)

      # (re)draw
      image = image.resize(display_size)
      render_to_screen(image)

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