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Zirojtan
12-24-2013, 09:04 PM
I am positive that someone has already asked this at some point but I thought I'd post a thread real fast since I don't want to go scouring the forum for an old topic on this matter.


So I know how to do four things on GIMP, really. These four things are selecting, cutting, moving the selection, and rotating it. Now, after I'm done doing these simple tasks, every time I save my modified gimp image, the pixels of the selection are messed up. As in, around the borders of where colors change, the colors are no longer solid, but some sort of weird transitional deal where they're all different.


Do you know what I mean?


This is especially annoying when my primary tool is Microsoft Paint. Every time I use GIMP to do something, I have to go back over with the pencil tool or the bucket tool and recolor all of the pixels that for no apparent reason changed to different color shades. Does anyone know how to get around this problem?

Azelor
12-25-2013, 12:16 AM
I think I know what you mean. This can happen if you change the file extension while saving and reduce the quality at the same time. Or not reducing the quality but saving in GIF.

So, how did you saved the file?

Another thing I need to say. If you go back and forth from a file extension to another (well actually it depend on the extension used), it mean that every time you do it the picture lose some of its quality. For example, I know a professional photographer that always modified his file in Photoshop and then compressed everything in a jpeg with no back up. And he could do this a couple of time with the same file. It does a very bad job.

To conclude, my advice is : if you can manage to use Gimp, you should stop using MSpaint since Gimp offers way more possibilities.

Zirojtan
12-25-2013, 12:40 AM
What do you mean by "file extension"? I'm sorry, I really am not tach savvy at all.


That being said, I usually just open the file that has been painted in MS Paint and then save it in GIMP and reopen it in MS Paint again, so I think I know what you mean here, but I'm not sure.


Also, I find GIMP to be incredibly complicated and frustrating, personally. Maybe that's cuz I haven't learned how to use it properly, but just what I have to go through to move a selected piece of an image and rotate it (right click here, right click there, go to this option, go to that option) is just... annoying. To me at least.

Larb
12-25-2013, 01:03 AM
The type of file you save your image as has an effect on what information it stores and what quality the end result is.

It sounds like you are working on an image, then saving it as a .jpg file. This is a "flat" compressed image file suitable for viewing on the web. The compression process results in a loss of quality - specifically the transitional area between colours and edges. It goes all weird close up (it is sometimes referred to as "jpg artifacting").

Basically you shouldn't use .jpg for a work-in-progress image.

If you are working between MS Paint and GIMP then I suggest saving your work-in-progress image as a TIFF file (.tif) or a bitmap (.bmp). You'll have the option to do that when you go to "save as". Only save your final ready image as a jpg if you intend to upload it somewhere. And keep a backup of your work-in-progress version so you always have a higher quality original should you ever need it.

Also! I'd suggest digging up some beginner GIMP tutorials on youtube or the web or wherever. I don't know what ones to recommend as I use photoshop myself but they will be really useful for getting to grips with the basics and it's stuff you'll pick up much quicker than you might think. Perhaps someone else can suggest some good ones.

Zirojtan
12-25-2013, 01:10 AM
Thank you, but I'm saving the file as the same png that it was before. The thing is that this kind of file compression or loss of resolution (when the pixels go crazy) is only happening on the piece of my map that I selected and moved to another spot. The rest of the image remains the same. It's really odd, and really kind of frustrating too.


I could probably do that later this week... I mean, I'm not really doing anything tomorrow, except working out. But I don't really want to hassle with learning a new computer program on Christmas day. Have you seen my map? My world is called Eurydice, and I have a topic on it in the Regional/World Mapping section. If you want, check it out. The only reason I ask is cuz I want to know if you think it would be easier to do what I'm doing in GIMP.

Falconius
12-25-2013, 02:48 AM
It could be the anti-aliasing or lack of, on your selection tool or perhaps you are feathering the edges on your selection tool. Try turning those off in the check boxes and see if you still have the same problem. Perhaps it could also be the interpolation of your selection transform tools? Try changing it to none and see if the problem still occurs.

Ghostman
12-25-2013, 05:05 AM
You might get better advice from us if you'd post some example pictures of before & after the editing. That way we could see for ourselves what you mean by changed pixel colors.

Zirojtan
12-25-2013, 01:57 PM
You might get better advice from us if you'd post some example pictures of before & after the editing. That way we could see for ourselves what you mean by changed pixel colors.


Now there's an idea! Where did you come by that sharp mind of yours? lol.


Ok, here's a picture of my world post editing on GIMP:

59927


I'm not exactly sure you can see exactly what's going on because of the maximum resolution that the image gets on this site, but can you see where I tried to use the bucket tool and the pixels have changed? Those hollow areas of color used to be solid right up to the edge, and so I could have used to bucket tool to change the color and there would have been no border remaining... before I edited it on GIMP. After I edited it on GIMP, the pixels change and they sort of blur the lines between colors where they were previously sharp, making it impossible for me to use the bucket tool to paint an entire section that is a certain color another color. I have to use the bucket tool, and it paints the interior only, and then I have to use a widened pencil tool for the edges. It's really, really annoying.

Zirojtan
12-25-2013, 02:11 PM
It could be the anti-aliasing or lack of, on your selection tool or perhaps you are feathering the edges on your selection tool. Try turning those off in the check boxes and see if you still have the same problem. Perhaps it could also be the interpolation of your selection transform tools? Try changing it to none and see if the problem still occurs.


So I just did both of these things, as you suggested, and the selection was unable to rotate. I would rotate it, and it would bring up a loading bar at the bottom that said "rotating" and then it would just stay put...

Falconius
12-25-2013, 03:22 PM
That could be a hardware or software issue, when I tried it it worked fine. Maybe try a clean install of GIMP? Or eliminate/consolidate layers where you can.

From the quick tests I did, I'm pretty sure that it is the interpolation causing the issue you describe.

waldronate
12-25-2013, 07:23 PM
If GIMP has a color index mode, make sure that you're not using that. Always try to do this sort of editing in RGB mode rather than color index mode, because the colors that the system may pick aren't necessarily the ones that you'd pick.

Midgardsormr
12-31-2013, 11:10 PM
I'm not familiar with Gimp, but what you're describing is very likely a filtering artifact, as Falconius said. For more information on filtering, read this thread: http://www.cartographersguild.com/tutorials-how/2596-%5Baward-winner%5D-bitmapped-images-technical-side-things-explained.html Posts 9-13 are the most relevant to this topic.

In a nutshell, though, if there is a filtering, anti-aliasing, resampling, or interpolation option (all four of those terms are roughly equivalent), you need to set it to either "nearest neighbor" or "none." It may be in the tool itself, or it may be a global setting. That will ensure that the software does not create any intermediate colors when transforming. Instead, it will pick the color of a pixel based on whatever whole pixel in the original shape that fell closest to it after the transform. Be aware that if your lines are less than three pixels wide, nearest neighbor filtering may create holes in the line after a rotation. That could interfere with your ability to bucket fill.

Based on the description of your workflow, though, I wonder if you might be more comfortable with vector software like Inkscape? Vector objects are not groups of pixels, but are actual shapes that you can manipulate to your heart's content without ever needing to worry about pixelization or filtering. It may take a little bit of time to learn the new tool, but you might find it better matches the way you want to work.

Redrobes
01-02-2014, 04:53 PM
Sounds to me like filtering - as said, try to use nearest neighbor filtering where you want to preserve the color to an original shade. Gimp may not have an option to set that for an operation like rotation or scaling as part of some other process. Ideally - as per my tutorial - its best to work in a res of 2x or 4x the original and then scale down the final and then its less of a problem. You should also have some options on the match threshold of bucket operation. I dont use Gimp so I cant say but usually paint packages have this. Just up the threshold a bit and it should include some of the pixels which are a shade near to the original.