Inverted Display --> AVI or GIF

[BPVietje]

I'm using AIJ to visualize and create a light curve for the near-Earth asteroid  2010 WC9.  I like to appearance if the inverted display (black stars/white background), but when I save stack as an AVI file, it always seems to revert to white stars, and ignore the brightness & contrast settings, so it looks terribly dark.

I'm hoping there is an easy solution.

Clear skies,

Brad Vietje
Newbury, VT
www.nkaf.org

[karenacollins]

Hi Brad,

I think you are meaning that when you save the AVI file and play it using another application it does not retain the display scaling (and inversion to black stars/white background) that you set and see in AIJ. If that is the issue, then this is what would be expected unless you modify the actual images that you use to produce the AVI. The image display scaling that you see in AIJ is simply modifying how the image displays on the screen in AIJ and doesn't modify the underlying pixel data. When you save the AVI, the movie is produced using the underlying pixel data, so other applications are not aware of the display settings you had in AIJ.

To accomplish what you are looking for, you will need to modify the underlying image data within your stack using the AIJ_Toolbar->Process->Math->Macro to modify the underlying pixel values to fit within a display range of 0-255.

A general method would be to set the AIJ display range to show the images the way you want it to appear. To do that set Image_Menus->Scale to "Fixed brightness and contrast" and then set the histogram sliders below the image until the image displays as desired. Then copy down the "Black" and "White" values from histogram display.

Next copy the string of text below and paste it into the panel at AIJ_Toolbar->Process->Math->Macro.

Black=500;White=1500;if(v<=Black) v=Black;if(v>White)v=White;v=v-Black;v=v*255/(White-Black);v=255-v;

Before pressing okay, replace 500 with the black value you wrote down and replace 1500 with the white value you wrote down. Now press okay. It will take a little time for the macro to modify your image stack values.

When AIJ has finished, move the histogram sliders all the way to the left and right of the histogram (i.e. to show the full range of pixel data). This display is how your AVI file will look.

If inversion to white background and black stars is not desired, use this equation instead:
Black=500;White=1500;if(v<=Black) v=Black;if(v>White)v=White;v=v-Black;v=v*255/(White-Black);

Karen