Quote Originally Posted by Redrobes View Post
You dont need to show the extents for me so long as the wip image is the same size as the others and you havent moved the shape withing the image. I have the mask all set up so I just take the new wip and apply the mask to it.

JPEG at 100% means no loss - or at least it ought to. That means it needs to encode every last pixels worth of information. JPEG works by working out the spectral content of 8x8 blocks of pixels and then encoding them in most important to least. The quality value tells it how many of the spectral components are encoded so as you reduce it then it knocks out more of the insignificant ones under some threshold. But with 100% that threshold is 0 and your supposed to do them all. So the difference from 100% to 99% could be quite a lot but 99% to 95% less so.

We had a challenge once to make a map but the image size in bytes had to be less than some value I cant recall but something like 64K and the map had to be > 800x600 or something. It was quite tough as you add detail the file size goes up. But we all learnt a lot about file sizes in that challenge. If your image has lots of normal detail in it then JPG is better if you have blocks of solid colour then often PNG can beat JPG in those situations. PNG is always lossless but JPG is normally lossy but with 100% it should be lossless - it does depend on the app tho. Also 5% in one app seems to be different to 5% in another. A drop of 5% in Gimp seems to be quite significant compared to other apps. I am not sure if JPG standard sets the exact method of how many or how much of the spectral components to drop with a determinate amount of quality value.
Ha! See - I learn quickly - quote the whole block you are answering or end up making a nonsense of the thread by getting ninjad in the middle

Its exactly the same. I even have a nice rectangle on the map to show the extent to pick once I've called the 'Rectangular Section JPEG' tool through the save menu, and I set the same pixel dimensions and use same map coordinates to define the exported map.

I used Corel Photopaint to reduce the file size - the export for web tool. I set the compression to 3% first and it was still over the limit - about 10 MB, so I went up to 5% and it turned out the one you see. I can't tell the difference, so I guess the loss must be in the texture of the background, which is nice and pale anyway, so it shouldn't matter.