Celestia Forums

Hello,

Can we easily invert dark background of Celestia in order to have a white one and make schemes?

Please see http://fr.wikipedia.org/wiki/Image:Prec ... t_fr_2.png

Thanks in advance.

Imy,

I don't know how difficult is it to add this function to Celestia, but if you don't have too much schemes to produce, maybe you can just post invert your Celestia pictures with Paint or something equal.

Here's an example.

Mathieu

Imy,

As Mathieu suggested, simply inverting Celestia screen shots in an image editing program seems like the simplest thing. I don't think there's much to be gained by making inversion a built-in feature for Celestia. One request that I am seriously considering is a feature to allow setting the background color to white instead of black. This would be useful for including Celestia-generated figures in papers, in which a black background is unsuitable.

--Chris

Thanks.

Well, a white background demands coloured stars. Commonly, stars are rather white, white on white, stars would dissapear, wouldn't they?

Inverting screen, using invert function from a photograph program or not, is still not the perfect solution (but it's a good start ) since, like your screenshot shows mathieu, Earth would be also inverted although it would be more interesting to keep planets in real colors. However i can still use a program to avoid inverting earth rectangle...

A special invert filter in photo function would be interesting i think. You would have only an inverted screenshot.

More advanced idea would be finally a sheme mode with celestia to use the program as a publishing tool. this could add others more or less useful options.

Imy wrote::?: Well, a white background demands coloured stars. Commonly, stars are rather white, white on white, stars would dissapear, wouldn't they?

Inverting screen, using invert function from a photograph program or not, is still not the perfect solution (but it's a good start ) since, like your screenshot shows mathieu, Earth would be also inverted although it would be more interesting to keep planets in real colors. However i can still use a program to avoid inverting earth rectangle...

A special invert filter in photo function would be interesting i think. You would have only an inverted screenshot.

More advanced idea would be finally a sheme mode with celestia to use the program as a publishing tool. this could add others more or less useful options.

You don't seem to be too familiar with image manipulation techniques.

All of your wishes are EASY to realize with a decent program like the GIMP or Photoshop. Firstly, you convert the sky to grayscale and apply a standart n-color dithering routine which will essentially leave you with whitish stars on a black background which is trivial to invert. It then looks precisely like the familiar professional astronomical prints of the sky.

Next if you want to leave some parts of the image in original color that's even easier. It's all a matter of exploiting some of the numerous fancy selection algorithms offered and to apply the above described procedure only to the selected parts of the image.

ETC.

I guess you agree that it does not make much sense to implement special custom and taste dependent filtering actions into Celestia's core code, when all this is easy to achieve with greater flexibility with popular dedicated software.

Bye Fridger

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chris wrote:One request that I am seriously considering is a feature to allow setting the background color to white instead of black. This would be useful for including Celestia-generated figures in papers, in which a black background is unsuitable.

--Chris

I was thinking, only a couple of days ago, how it would be good to have a white background, or perhaps even set the background colour to any chosen RGB value in celestia.cfg (default RGB(0,0,0) of course )

This would be very handy, and for this purpose stars would not need to be inverted as in all likelihood star and galaxy rendering would be switched off completely in this situation.

>symaski62 : aright this is the same field : have you noticed that ursa contellation is larger?

All of your wishes are EASY to realize with a decent program like the GIMP or Photoshop. Firstly, you convert the sky to grayscale and apply a standart n-color dithering routine which will essentially leave you with whitish stars on a black background which is trivial to invert. It then looks precisely like the familiar professional astronomical prints of the sky.

Next if you want to leave some parts of the image in original color that's even easier. It's all a matter of exploiting some of the numerous fancy selection algorithms offered and to apply the above described procedure only to the selected parts of the image.

I'm not a specialist of image manipulation, it's true. However, using a high-pass filter (or a low) or stuffs like that, allow you only to select stars. It could be useful. But in this case you keep dark background and you're going to use more ink in a possible printer edition ; without dealing with paper support, it seems that human eye is more sensitive to the contrast with white backgrounds (and so it's easier to use the screenshot for an explanation).
I think we're togeter dealing with possible ways for publishing screenshots from Celestia otherwise that with an image or a movie.

I guess you agree that it does not make much sense to implement special custom and taste dependent filtering actions into Celestia's core code, when all this is easy to achieve with greater flexibility with popular dedicated software.

I don't agree with you. I think these functions would be interesting even in Celestia. It would be an additional feature besides contemplating universe and learning how cosmos is. Reading this forum, it seems that others universe simulators exists, and they are quite similar...
Everyone doesn't know that such image program exists. And when they have listened names like GIMP and Photoshop or PSP (...), they surely doesn't use it and doesn't know how to use it.
Even if Celestia users use this kind of program, wouldn't they be interested to play with only one program, using simplified and specialized (for astronomy) functions?
I haven't in mind to transform Celestia in GIMP but only to give tools for Celestia user like photograph or movie functions that are already in core program.

Imy wrote:>symaski62 : aright this is the same field : have you noticed that ursa contellation is larger?

All of your wishes are EASY to realize with a decent program like the GIMP or Photoshop. Firstly, you convert the sky to grayscale and apply a standart n-color dithering routine which will essentially leave you with whitish stars on a black background which is trivial to invert. It then looks precisely like the familiar professional astronomical prints of the sky.

Next if you want to leave some parts of the image in original color that's even easier. It's all a matter of exploiting some of the numerous fancy selection algorithms offered and to apply the above described procedure only to the selected parts of the image.

I'm not a specialist of image manipulation, it's true. However, using a high-pass filter (or a low) or stuffs like that, allow you only to select stars.

By God NO. Who told you?

Suppose -- as you suggested-- we have an image with a colorful planet in front of a black sky with many stars. You could select e.g. the Planet (e.g. by color ) and invert the selection. Then the whole sky (apart from the planet!) is selected! Then you convert the selected sky (including the stars) to grayscale. Then you put your white threshold appropriately and dither the sky e.g. only into black and white. Then you invert the sky which then gives you a beautiful colored planet in front of a monochromatic white sky and many black stars. By playing with the white threshold (before the dithering) you can vary the effective sizes of the stars somewhat according to gusto.
(did you understand why?)

The whole operation would take me NOT more than 5 minutes.
I can easily provide a demonstration if you still don't know how to do this. Moreover, in professional image manipulation programs you have sophisticated printer drivers with previewing etc, quite unlike what could ever be incorporated into Celestia!

t00fri wrote: I guess you agree that it does not make much sense to implement special custom and taste dependent filtering actions into Celestia's core code, when all this is easy to achieve with greater flexibility with popular dedicated software.

I don't agree with you. I think these functions would be interesting even in Celestia. It would be an additional feature besides contemplating universe and learning how cosmos is.
...
Everyone doesn't know that such image program exists. And when they have listened names like GIMP and Photoshop or PSP (...), they surely doesn't use it and doesn't know how to use it.

People who would NOT know about GIMP or Photoshop are definitely RARE in this general area of interest! It is clearly impossible (and really NOT motivated) to incorporate and thus redouble a number of image manipulation functions into Celestia which would make the program unnecessarily heavy. You may prefer colorful planets in front of monochromatic inverted skies. Someone else may want a different variation. So a whole palette of custom image manipulation features would be needed in Celestia's core to satisfy everyone's wishes. Clearly impossible, whether you agree with me or not

Who then would be aware of such unexpected abilities of Celestia among those who have never heard EVEN of world leader graphics software like Photoshop or the GIMP

Bye Fridger

I was only dealing with a simple function that inverts background. It could be a simple function to develop Celestia image publication. It's surely a
gross function.
Publishing image would need a particular mode of Celestia to satisfy all possibilities in easy way. And for instance to keep selected objects like planets in real colors, or keeping special colored stars, or having stars like circles (full or not, cross) according to their size... An another mode where performance would be secondary.
I appreciate your suggested image manipulation. But if you needed 5 minutes, others less interessed in computer science need more time. However, I think everyone which uses an astronomy program doesn't want to deal with computering stuffs. I think it's even contradictory to Celestia interface : handy and simplifed. User doesn't need to know programmation or commonly interface rules. He wants only universe !
It's sure that GIMP (or others) is quite an heavy program. And problably specialists would prefer this. But starting publishing with Celestia offers possibilities to make pre-processing functions and post-processing operations (like basic image manipulations).

My one cent. Both reasons stands in both sides. Fridger for the code, Imy for the history. Does it would result an hard code which would heavy the program, it should better accomplish the change within the Lua routines, if possible. The white background, though, is that of the books of astronomy, past and present.

My TWO cents...

Why on Earth does this functionality even need to be discussed
here? Not only are there many high-quality image processing
programs available to do this stuff, but there are also many, MANY
free (and very easy to use) programs which also offer the ability to
manipulate backgrounds, replace colors, and basically set up your
images for use on a white piece of paper.

I really do NOT understand this thread. Can someone elucidate for
the Brain-Dead? Why is this such a big deal?

Thanks, Bob

I really do NOT understand this thread. Can someone elucidate for
the Brain-Dead? Why is this such a big deal?

Having Celestia inverting the background for print (or other media) is pointless, as several has pointed out; if you want to use a screenshot in any medium, you have to go through an image editor to prepare the image anyway, and setting the bgcolor to white in the process is a trivial operation.

Now, if Celestia could output vectorized images, that *would* be a big deal... But that??s not going to happen... But wow, how cool that would have been...

- rthorvald

you could make the inverse color with an nvidia tool thet comes with the display driver
look for it in display settings

mjoubert wrote:Imy,

I don't know how difficult is it to add this function to Celestia, but if you don't have too much schemes to produce, maybe you can just post invert your Celestia pictures with Paint or something equal.

Here's an example.

Mathieu

That's cool! It's like the counter clock universe.

Now, if Celestia could output vectorized images, that *would* be a big deal... But that??s not going to happen... But wow, how cool that would have been...

That's one reason for what i've called pre-processing functions that any others outter program can make...

You can invert image with whatever you want, but it's sure that if it is in Celestia it could be better, one program, on click, one solution. it's the easiest. Only inverting Celestia windows would not be so heavy : for windows version, it's only one line for one API and I suspect that for OpenGL code library is so quick. Finally, basic inverting function would probably need only few lines, i think.

Imy wrote:

Now, if Celestia could output vectorized images, that *would* be a big deal... But that??s not going to happen... But wow, how cool that would have been...

That's one reason for what i've called pre-processing functions that any others outter program can make...

You can invert image with whatever you want, but it's sure that if it is in Celestia it could be better, one program, on click, one solution. it's the easiest. Only inverting Celestia windows would not be so heavy : for windows version, it's only one line for one API and I suspect that for OpenGL code library is so quick. Finally, basic inverting function would probably need only few lines, i think.

Yes and after taking just a little breath above, you went on requesting to only invert the background sky while leaving the planets in full color!!

THAT is an entirely different level of image manipulation. For this one needs fancy selection algorithms, one has to struggle with aspects of anti-aliasing and many other things.

Usually such ventures are said to only require a few lines of code, and --faster than the initial code is implemented-- new requests for more fancyness are formulated by the same users

Bye Fridger

rthorvald wrote:

I really do NOT understand this thread. Can someone elucidate for
the Brain-Dead? Why is this such a big deal?

Having Celestia inverting the background for print (or other media) is pointless, as several has pointed out; if you want to use a screenshot in any medium, you have to go through an image editor to prepare the image anyway, and setting the bgcolor to white in the process is a trivial operation.

Now, if Celestia could output vectorized images, that *would* be a big deal... But that??s not going to happen... But wow, how cool that would have been...

- rthorvald

It's pointless if we need that Celestia does show VT's, star colors or super details, that is all that would transform Celestia in what primarily it isn't: a render engine like Maxwell Render, Virtual Light, etc; as well as they primarily aren't space simulator. It's not pointless, however, with a "print" function that could tell of not printing the background, so the white were that of paper and for the rest make all black (I don't know how complex might be, of course); that is, just geometry and labels, for a quick (and then massive for the laser printers) output of the signs and of planetary positions, on drop a pen for reminds, thoughts and educational purposes in the classrooms.

THAT is an entirely different level of image manipulation. For this one needs fancy selection algorithms, one has to struggle with aspects of anti-aliasing and many other things.
Usually such ventures are said to only require a few lines of code, and --faster than the initial code is implemented-- new requests for more fancyness are formulated by the same users

Basic inverting of all window without another restrain is a first step. But surely considering more options would be easier if we consider the image before it is made instead of after it has been processed by Celestia and in this last case, complicated image manipulations have to be used to get a worse final quality image.

It's pointless if we need that Celestia does show VT's, star colors or super details, that is all that would transform Celestia in what primarily it isn't: a render engine like Maxwell Render, Virtual Light, etc; as well as they primarily aren't space simulator. It's not pointless, however, with a "print" function that could tell of not printing the background, so the white were that of paper and for the rest make all black (I don't know how complex might be, of course); that is, just geometry and labels, for a quick (and then massive for the laser printers) output of the signs and of planetary positions, on drop a pen for reminds, thoughts and educational purposes in the classrooms.

I like this. An easy way to satisfy all possibilities for printing solution from Celestia is only considering edges, geometric edges that we may be fulled with a particular color later. Vectorized images would be then obvious.
Even Edges could be only a circle for a planet (and then can't we full it with a texture even so?)
More than a print function what about a print view?[/quote]