Should file size be bigger after saving with IrfanView?

[pdun459]

Hello fellow IrfanViewers.

I've started noticing that when I open an image with IrfanView and simply save it without any editing at all, the file size is always bigger than when I started. I have to set the save quality to 80% to get the file size to stay the same.

I only have the standard plugins that come with IV installed, nothing more. I've checked and I can't find any settings I might have changed to cause it. Does IV have some kind of built-in upsampling? Just curious if anyone knows anything about this.

Thanks!

[Bhikkhu Pesala]

It depends on how much compression was applied to the original JPG that you opened and saved. If it was taken straight from a camera, saving it at a quality of 80 will generally make the file size considerably smaller. If it was originally saved at a quality of 50, saving it at 80 will add some new artefacts, increase the number of colours, and make it bigger without the slightest improvement in quality, and in fact a slight almost undetectable degradation.

Read the sticky thread: Resizing Images with IrfanView.

[pdun459]

I thought if you set save quality to 100%, IrfanView would simply match whatever the original was. That is, if the original quality was 50%, IrfanView would recognize that and save the file at the original compression and file size. But apparently there's a lot I don't understand about it. I just installed RIOT. I figure it's a lot easier to let it figure it out.

Thanks Bhikkhu Pesala.