There are some differences in the “libraries” that are used for image processing.  It is important to determine which is best for your application.  Below is a quick visual summary of 5 and 10 px gaussian blurs from a dozen or so programs.  Inkscape is missing, as I could not find the specific term “gaussian” for any blur filters.  Most of these programs are similar but some are expensive to purchase, or have a monthly contract for, others are free software.  While i really do like photoshop (two versions here) and corelDRAW and corelPhotopaint (two versions here), ImageJ is easy to use and provides pretty comparable results albeit on a very much smaller selection of effects and filters to the former programs.  The bar marker example here was a vector box (no outline) layered onto an image,  exported as a tif and processed in these programs as such.