staramp: A C repository from bashrc2

staramp detects stars within a night photo and then amplifies only the star pixels by some defined percentage, without altering the background.

Installation

On a Debian based distro:

sudo apt install build-essential

Then build and install:

git clone https://gitlab.com/bashrc2/staramp
cd staramp
make
sudo make install

Usage

An example of use can be seen within the test.sh script.

staramp --dog 8 --dogthresh 145 --dogamp 80 --miny 0 --maxy 2100 -f images/stars1.png

It produces a file called result.png

--dog specifies the radius for the difference of gaussians filter. It should be approximately the same as the width of the stars in pixels within your image.

--dogthresh applies a threshold to the difference of gaussians filter, so that faint pixels which might just be noise can be excluded.

--dogamp the amplification percentage.

--miny sets the minimum Y axis coordinate to begin processing at. This is typically 0 (the top of the photo).

--maxy sets the maximum Y axis coordinate to end processing at. This can be 0 which means process the whole image, or it can be some other value to exclude any scenery at the bottom of the photo.

-f defines the night image to be processed. This must be in PNG format.

You can also exclude areas of the image within specified bounding boxes, by using the --exclude option:

staramp --dog 12 --dogthresh 140 --dogamp 70 --miny 0 --maxy 0 --exclude "0,1590,1287,2013" -f images/stars2.png

Here the bounding box to be excluded has top left coordinate 0,1590 and bottom right coordinate 1287,2013. If you specify additional numbers then you can have multiple exclusion areas. An example might be:

--exclude "(0,1590,1287,2013),(50,100,300,500)"

If excluding bounding boxes is insufficient, because the shape of the scenery is not very linear then you can define a polygon inside which the stars should be amplified. The polygon can have up to 127 vertices and is a series of x,y coordinates. For example:

staramp --dog 12 --dogthresh 140 --dogamp 70 --miny 0 --maxy 0 --inside "(0,0),(3045,0),(3045,2019),(1278,2019),(936,1587),(0,1572)" -f images/stars2.png