Creating the reference file.

A dust bunny reference file (.dbr) is a text file containing the x/y
coordinates and sizes of the dust bunnies on a .jpg or .png image.
Therefore, the first thing you need is an image where each dust bunny
is plainly visible.

An easy way to create such an image is to take a picture of a white sheet
of paper. Set the camera to manual focus mode, and set focus to infinity.
Use aperture priority and set the aperture to a small opening such as f22.
Take the picture so that the sheet of paper takes up the entire frame. It
doesn't matter that the paper sheet is out of focus or blurred due to camera
movement. All you care about is seeing the bunnies on the sensor.

Another easy and commonly used method is just to take a picture of a clear
blue sky.

Once you have the image it may help to adjust the brightness and/or
contrast in an image editor in order to see the bunnies better.

Now start dbblast. Go to the "File" menu and "Create Reference File",
and open the image you just created. Mark each dust bunny by right clicking
in the bunny, then select "Mark" from the popup menu.

You can use the mouse to move the marker circle and the mousewheel to
resize it. Or you can use the arrow keys and plus or minus keys on the
keyboard. I think the keyboard gives a little finer control.

You can also go back to any previously created markers, and by right
clicking you can move, resize, or delete the marker by selecting the
appropriate item from the popup menu.

Note: It's important to position each marker circle as accurately as possible.
The size should be larger than the bunny, i.e., you should be able to see the
background of the image all the way around the bunny between it and the marker
circle itself. But don't make the circle larger than that. You may need to
experiment to see which size works best.

When all the bunnies are marked, go to the "File" menu, and
"Save Reference File", and save the file. The suggested file name is
default.dbr. but you can name it anything as long as it has the .dbr extension.
(The reason default.dbr is suggested is to make it simpler to use the command
line utilty, which looks for the file "default.dbr".)