Allow to copy the PPI value from the Resize PPI box to metadata DPI

[sguyader]

Currently, in the Resize tool there's a PPI box which allows to calculate the dimensions of the image if it were to be printed at the said resolution in DPI. However, it's a just giving information, and changing the PPI value only updates the calculated dimensions but doesn't change the actual resolution of the exported image, which stays at the default 72 DPI. It up to the user to modify the XResolution and YResolution values in the Metadata panel to reflect the PPI value.

This seems to be confusing to users who think that changing the PPI value should also change the DPI resolution of the exported image.

This pull request simply adds a "Copy PPI to EXIF" button below the PPI box, allowing to copy the PPI value to the [X|Y]Resolution in the Metadata, which get encoded into the exported image EXIF.

[agriggio]

Hi, thanks for the idea! In principle I like it, but I would prefer a checkbox instead of a button, so that you can put that preference in an .arp file and the values are kept in sync when changed. What do you think about that?

[sguyader]

I like you idea of a checkbox. Since I'm not really used to pull requests and modifications to pull requests, how should I proceed? Just modify the code, try it, and create a new pull request?

[agriggio]

You can also continue working on your branch and let me know when it's ready. No need for another PR. And thanks!

[sguyader]

I pushed changes to my branch. The button is replaced with a check box, and when checked the PPI value is copied to the metadata. I made sure that new values entered are always copied even if the the Resize tool is disabled. Also, when the box is unchecked the metadata are reset to default values (loaded image EXIF values if they exists or 300 dpi if there are no EXIF values, if I'm not mistaken).

[agriggio]

Thanks for the contribution! I've merged with some tweaks, I'll close this