Correction of multiplicative shading, due for instance to uneven
No other image (background, illumination, etc) is required, as for
other ImageJ plugins.
April 2003: Development of the plug-in by Maxime Pinchon.
August 2004: Version 1 available on the Web
September 2004: Improvement of the output image (larger dynamics).
Thanks to Joel Sheffield.
June 2005: Extensions by Laetitia Pasquet (v3= version 3), after
suggestions by Gabriel Landini:
The plug-in is extended to work with 16 or 32 bit-images and RGB color
automatic version is proposed, without guarantee (because the selected
markers are not constrained to be in the background). The polynomial is
no more constrained to be of order 2. The polynomial degrees along X
and Y are chosen by the
user, up to 5.
The user has to choose the automatic version (click in the
appropiate position (see below) and choose the positions of the
reference points) or the semi-automatic version. If nothing is clicked,
the user is assumed to choose the semi-automatic version.
The markers are regularly spread over the image (without any
guarantee that they belong to the background). So, this method is to be
used with care.
The user has to click on several (at least 6, better
someting like 10 or 12) positions assumed to belong to the
"background". The positions and gray levels at these points will serve
to model the background, and thus
For this purpose, a new toolbar is created at the beginning of the
Items of the toolbar (1 to 5 from left to right):
1: start clicking
2: move point
3: delete last clicked point
4: coordinates of clicked points
5: starts computation
In both modes:
The program computes a background model according to the degrees of the
polynome chosen by the user.
For instance, a second order polynomial along X and Y is modelled
as: B(x,y)=a0 + a1.x + a2.y + a3.x^2 + a4.y^2 + a5.x.y
The raw image is divided by the estimated background.
When the graphic mouse leaves the image window, this window may move
behind others and become hidden by these ones. It is thus recommended
to maintain the mouse within the image window or to reduce the size of
Illustration (semi-automatic mode):