Resize image

use QT :)
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from qt import QImage
import sys

qm = QImage(sys.argv[1])
qm = qm.scale(600,480,QImage.ScaleMin)
qm.save('ch-'+sys.argv[1],'JPEG',100)

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o/p is good enough

Update:

If you find the output image is not good enough, then you might want to use
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qm = qm.smoothScale(600,480,QImage.ScaleMin)
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