[Image-SIG] [image-sig] controlling brightness of the image

[Fredrik Lundh]

Amos Newcombe wrote:

> > img2.save("xyz1.jpg" + ext, "JPEG", quality=100)
 >
> (I haven't checked your other steps. The save() call looks unnecessarily 
> complicated, but I don't know what code you've cut out.)

quality=100 is a bad idea, at least.  quoting myself from an earlier post:

   JPEG quality 100 is overkill, btw -- it completely disables JPEG's
   quantization stage, and "mainly of interest for experimental pur-
   poses", according to the JPEG library documentation, which
   continues:

     "Quality values above about 95 are NOT recommended for
     normal use; the compressed file size goes up dramatically
     for hardly any gain in output image quality."

As for suitable settings, the documentation recommends the following:

    "/.../ the quality setting should be between
    50 and 95; the default of 75 is often about right.  If
    you see defects at quality 75, then go up 5 or 10
    counts at a time until you are happy with the output
    image.  (The optimal setting will vary from one image
    to another.)

For the full excerpt from that documentation, see:

     http://mail.python.org/pipermail/image-sig/2002-July/001916.html

regards /F