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hjsmuc

Tips for orthophoto makeover

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Does anyone know a good tutorial (text preferred to video) on orthophoto improvement? What I dislike most are the color differences. E.g., I would like get one half of the image to have the same colorization as the other half which is often not the case if the picture is composed of two or more satellite shots. I am completely unskilled when it comes to Photoshop and Gimp so looking for something intuitive. Thanks for any advice.

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Whenever I've done it, I make extensive use of the color match in photoshop, basically I use the mosaic tool in the Utils folder for Ortho4XP to merge a region of orthos together into a large image, and then I select the discoloured area, use colour match and it works almost everytime (unless it's drastically different). I then clone out the hard edge, so it's hard to even see where the original match was done. In short, I only make use of selection, colour match and the clone brush

 

However, you need to badly want it to look good though and it takes some patience. I only did a few tiles around my home town, which also involved using three different sources (cloning bits from one into the other). I now have a large area around my home with bandless orthos, so I'm happy. But I wouldn't want to do anymore, it takes way too much time if the area is bad.

 

The best solution would be for a community effort to share the edited jpegs. But not all of the sources can be redistributed.

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Whenever I've done it, I make extensive use of the color match in photoshop, basically I use the mosaic tool in the Utils folder for Ortho4XP to merge a region of orthos together into a large image, and then I select the discoloured area, use colour match and it works almost everytime (unless it's drastically different). I then clone out the hard edge, so it's hard to even see where the original match was done. In short, I only make use of selection, colour match and the clone brush

 

However, you need to badly want it to look good though and it takes some patience. I only did a few tiles around my home town, which also involved using three different sources (cloning bits from one into the other). I now have a large area around my home with bandless orthos, so I'm happy. But I wouldn't want to do anymore, it takes way too much time if the area is bad.

 

The best solution would be for a community effort to share the edited jpegs. But not all of the sources can be redistributed.

 

Not publicly but I guess if we could arrange a private repository that would help a lot, I read who has uploaded a reworked tile and just send him a PM to get the link. I'm about doing that for Crete and Cyclades, I have wasted enough time on those tiles to save the same time for others.

 

Do you know if the same process can be done on Gimp, i.e. what Gimp tool correspond to mosaic, color match and clone in PS? Gimp being freeware is a must for many amateurs.

How do you split them later?

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Thanks Tony, would you be so kind to elaborate a bit more about the mosaic tool? I saw the mosaic.py file but I have no idea how to apply it and merge some orthos.

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How do you split them later?

 

The mosaic tool will both split them and join them. You can find it in the Utils folder in Ortho4XP.  It's been some time since I've used it, but it was something like

 

"mosaic assemble latmin latmax lonmin lonmax", which produces a very big file that you can open in GIMP or convert to TIFF and open in photoshop, so make sure you either use smaller areas or have the memory to support. An entire tile at mid latitudes is about 10GB for ZL16, but you can do smaller areas and it works the same.

 

Then once done editing the monster image, you use the mosaic tool again, but this time use split, and it cuts them back up again ready to placed over the original jpegs. I found that I could generally do it without pain by splitting the tile into 4, but if you have more RAM, you could probably do the entire tile.

 

 

 


Do you know if the same process can be done on Gimp, i.e. what Gimp tool correspond to mosaic, color match and clone in PS? Gimp being freeware is a must for many amateurs.

 

Almost certainly you can. At least I'm certain GIMP can do cloning, and colour matching (if it doesn't you can adjust the colours yourself to get it close enough). Maybe someone else here who uses it can help you out, as I haven't used GIMP for years.

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