Smoothing a line?

[JoeB]

[It is an interesting challenge you submitted !:>)

I agree! These types of questions get people to start thinking outside the box and tend to generate different approaches, which is great as a learning process for using different methods of achieving a goal. I, for one, enjoy attempting to solve these types of questions and also reading how others approach them!

[JoeB]

I'm also reconsidering the effectiveness of any method based on covering up or expanding the original jagged line. Even in the best result so far, from hartpaul, you can see unrealistic, vertical steps. I might instead focus on smoothing the original GPS recorded track mathematically.

As you said, the devil is in the details. And in that vein I'm not quite sure what you mean by "unrealistic, vertical steps." If you mean that there is still too much jagginess in hartpaul's attempt then that is easily fixed just by using more smoothing from the Selections>Modify>Smooth dialogue. Here is an example of a smoother type of elevation line. The amount of smoothing is, of course, variable so can be set to taste.

In other words, I am interpreting your request to say that you want a thick line that follows the "general" contours of the elevation line and eliminating the more precise, sharp contours that we've been calling jaggies.

You have to click on the image to see it full size.

[hartpaul]

Hi Terrypin,
The bottom Layer is the one on the bottom in your layers palette, while the second layer is actually the top layer. Don't over think it and compare with other programs
The bottom layer is the one you do selections on so you could also label that Selections layer. The top layer is the one where you place your fill so that it covers the bottom layer.
So Selections, and modify selections at the bottom and fill on the top layer for the inside and the line part.

[terrypin]

As you said, the devil is in the details. And in that vein I'm not quite sure what you mean by "unrealistic, vertical steps." If you mean that there is still too much jagginess in hartpaul's attempt then that is easily fixed just by using more smoothing from the Selections>Modify>Smooth dialogue. Here is an example of a smoother type of elevation line. The amount of smoothing is, of course, variable so can be set to taste.

In other words, I am interpreting your request to say that you want a thick line that follows the "general" contours of the elevation line and eliminating the more precise, sharp contours that we've been calling jaggies.

You have to click on the image to see it full size.

Excellent, thanks Joe.

First, yes, that sort of result is exactly what I was seeking.

Your post not only got me using the Selections>Modify>Smooth dialogue in earnest for first time, but, more important, also had me doing some thinking I should have done earlier. I've belatedly realised that I've been making this exercise unnecessarily difficult in two major respects:

1. Working with JPG files.
That loses the colour integrity of the originals (mainly screenshots captured with Snagit or occasionally the Prt Scr key). Instead of immediately saving the image as a JPG in IrfanView, which I do in most work, for these elevation profiles I will now work in PSP 8 with the originals, saving any intermediate files in ither BMP or pspimage format. So the sort of editing I want to do on the line, such as futher smoothing for visual appeal, enlarging it, changing its colour, etc becomes much easier.

2. Ignoring 'Garbage In, Garbage Out'.
I have mapping program tools to smooth GPS data in varying degrees and it was foolish to compensate for omitting that step by tring to emulate it in PSP.

For similar profiles in future I’m also going to scale them from zero (I.e. sea level), which will further reduce any jaggedness.

[JoeB]

Glad to see that we now have your goals properly identified.

Yes, if you have other tools that you are familiar with using and that can help solve your concerns then of course turning to them first is a good choice. Otherwise, as you can see from my last attachment, it's quite easy to achieve what I did just using PSP, and the steps can be scripted to make them automatic or as automatic as you like, with the ability for user input for some stages if desired. If the images are going to be different sizes, for example, then you would require some user input to change the thickness of the line proportionate to the image size or size of the jaggedness you wish to hide. But even so a script would certainly speed up the process.

And I would suggest that, working with PSP, you save your intermediate images in pspimage format so as to preserve all layers, etc., while at the same time making sure your saves are lossless. Final versions can, of course, be also saved in whatever format works best for your purposes. But still keep the final version also in PSP format just in case!