It's Full of Stars -- Discussion about Star Generation

[anthony]

This is a continuation of a off-subject thread from viewtopic.php?f=5&t=8668

this includes disscussion about real photos of stars

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wget http://www.cit.gu.edu.au/~anthony/saves/southern_stars.jpg

As it is the 8 second exposure (from the EXIF header) gives the stars a 2 to 3 pixel streak, caused by earths rotation. That however is the longest exposure posible on my camera (shame star streaks make good photos Laughing ).

Using a IM example developed 'star generator' for image highlights

http://www.imagemagick.org/Usage/advanced/#stars
That geneator can create not only 6 ray, but 4, or 8 ray stars, and with a little tweek could make the alturnate rays in an 8 ray star dimmer, or a slight color shift doe a even better effect.
That is I have a shape, or image that has a highlight in it. I want to reduce that image to all black except for the center of that bright highlight. That image can then be 'starred' and overlayed back onto the original image. Instant star spot at the right location.
If the image is part of a animated sequence involving a moving light source, then the 'star' position will move from image to image, add a little rotation each time. You animation will then have a star 'rolling' along with the highlight in the image
The problem is I have not figured out a good automatic way to find the highlight points.

Using Dingbat Stars

I also worked with a umm. I guess it's call a math algorithm? It does the random changing of the stars layout with each refresh. Uses dingbats for the star shapes. Looks like a swf when a friend showed it to me. It's IE browser view-able only tho. Can't see a thing with firefox. Had to open it with IE in order to see it.

I wouldn't like to rely on a font for stars. as it would be difficult to exactly position the image.
However the Dingbats stars are rather nice. Maybe a 'create a random star animation' script using dingbat fonts would be a interesting excerise (random star selection, rotation, with some limited point size changes).

And firefly or (moving and looping stars)

http://scri8e.com/stars/ani/3_fireflies/
I think the fireflies will need a bit of programming to geneate closed mathematical loops of different sizes, shapes and styles. The 'flys' could then return to the start point smoothly so as to repeat without a sudden 'jump' in position as the animation loops.

And so on.. All welcome.

[scri8e]

prehaps we could go to a new forum subject?

"It's full of stars!" -- 2001 A Space Odyssey ?

I'm all for it! Let's get star struck, starry eyed, comet tailed!


I recently picked up a cannon PowerShot A540 digital camera. Nothing high tech. I love the darn thing tho. Talk about settings!
There are 3 manuals that came with it. About all I have done is point and click, upload pics and delete to free memory. Had it about a month. It will take movies also.

Then there is the other toy. A flat bed scanner. .. LOL@me ....
Yap Yap Yap ...

....................

This should be fun!

[anthony]

Anthony commented...

just a quick word... -reverse is now availabel on the latest (dated 20 March or later).
See IM examples Aniamtion Handling
http://www.imagemagick.org/Usage/animations/#reverse

Great news on the reverse!

Yes this should make it a lot easier to do some flares.
though it wouldn't help with flares that als rotate with asymetries.


Once I finish with 'Optimizetransparency' I will be doing Layer Composition operators, which should make overlaying animations a lot easier.

I recently picked up a cannon PowerShot A540 digital camera.

Tried photographing real stars yet?

[scri8e]

Excellent! Quite a dazzling 3-some you have created.

[anthony]

I didn't create, but throught I'll throw them into the discussion. I figured you'd like.

[anthony]

Hmmm just a question for scribe. Can you tell me (or better still publish on your stars web site main page (on that page or a link from that page)....
(yes I know or can guess what they mean, but want to know for reference in generating Examples for generating these things (both me and others)

For GIF animations... What is your definition of...

• stars
• star clusters
• glitter
• sparkles
• flares
• fireflies
• flashites
• blinkies

and anything else. (You seem to like the '...ies' phrase )

I have also done some updates to the 'stars' canvas creator, and am considering a dual-random-canvas approach for better control and color definitions.

[anthony]

Interesting way of getting a 1% random field of dots in a shape defined by a mask.
Dots are however impulse values (just on/off)

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   convert  mask_image.png   +noise Multiplicative \
               -solarize 50% -colorspace gray -normalize \
               random_dots_in_shaped_area.png

[anthony]

You can also reduce the amount of glitter by a 1/3 if you extract one
color channel as a glitter mask.

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   convert  mask_image.png   +noise Multiplicative \
               -solarize 50%  -channel G -normalize -separate +channel \
               random_dots_in_shaped_area.png

I still think a better result (with a more varible intensity in the glitter dots) can be achieved using two pure random images. I'll have to look at at least expanding +noise to return a pure random image (as a FAST "-fx 'random()' " ).

Then you can use thresholds and composition to set exactly what percentage of 'glitter' you want, and even multiply it with a mask to 'shape', or even 'fade' the glitter around the edges.

After that some very light -blur, -normalize and -sigmoidal-contrast can be used to enlarge 'dots', (depending on intensity) and make a 'nicer' looking glitter.

[anthony]

Some news... With the impending release of IM v6.3.5 a +noise Random has been added. This makes creating random stars a lot faster than the -fx method.

[anthony]

More news. I finally added the initial glitter examples for command line use
http://imagemagick.org/Usage/anim_mods/#glitter
More examples, or contributed examples (can you help) to come.