[Digikam-users] png huge

[Andrew Goodbody]

Martin Senftleben wrote:
> with the many replies to my question I still believe I haven't been 
> understood properly, even though I am very grateful for the replies 
> which helped me to understand things better.

.jpg is a description of an image. The image is not described completely
(ie it is lossy) so the reconstructed image is only an approximation of
the original. The .jpg decoding process fills in for the lost
information as best it can.
.png records the whole of the image, both the parts provided by the .jpg
information and that filled in by the .jpg codec. This is where the
apparent extra data comes from.
But as others have said they record the image in such a different way
that the comparison is not fair, the size of the file is not an accurate
guide to the amount of information contained in it. In fact with a high
quality .jpg file it can be bigger than the corresponding .png but still
lose information that was contained in the original.

Andrew