This menu groups operations which filter images, or
which are filters in the photoshop sense.
    
- 
Convolution 
- This
    menu has several standard convolution operations
    (blur, sharpen, edge detect, etc.), plus the option to
    convolve with a custom kernel.
    Two  menu  items  are  slightly  more  complicated.
    Unsharp Mask transforms to CIE LAB colour space,
    then sharpens just the L band with a cored unsharp
    filter. The Tasks  / Print  menu has a version of this
    filter tuned for typical inkjet printers.
     Custom Blur builds and applies a square or gaussian
    convolution  kernel  for  you  based  on  a  radius
    setting.
     
- 
Rank 
- A  preset  median  filter,  and  a  custom  rank  filter
    that lets you specify window size and rank.
    The Image Rank item does pixel-wise ranking of a
    set of images.
     
- 
Morphology 
- 
    These menu items implement basic morphological
    operations.  Images  are  zero  for  background  and
    non-zero  (usually  255)  for  object.  Matricies  are
    shown  as  0,  1  and  *  for  background,  object  and
    don’t-care.
    The Threshold  item does a simple level threshold.
    Use  the  Math  /  Relational  menu  to  construct  more
    complex image binarisations. Use Math / Boolean to
    combine morphologies.
     The  first  half  of  the  menu  lists  simple  erode
    and  dilate  operations,  4-  and  8-way  connected.
    The second half contains several useful compound
    filters.                                              See  also  Histogram   /  Find  Profile   for  something
          that  can  search  an  image  for  object  edges.  And
          MathStatistics / Edges can count the number of edges
          across and down an image.
           
- 
  Fourier  
- A selection of ideal, Gaussian and Butterworth
          Fourier space filters.
          You can make other mask shapes yourself using the
          Image / Make Patterns menus, then apply them using
          Math / Fourier. You can also use the image paintbox
          to directly paint out peaks in a fourier-space image
          before transforming back to real space.
           
- 
  Enhance  
- A  selection  of  simple  image  enhancement
          filters. Statistical Difference passes a window over an
          image  and  tries  to  match  the  region  statistics  at
          each point to a target mean and deviation.
          
- 
  Spatial Correlation  
- Place a small image at every possible
          position   in   a   big   image   and   calculate   the
          correlation at each position. Simple Difference is the
          much faster unnormalised version.
          
- 
  GREYCstoration  
- VIPS                                        includes
          a copy of the CImg library and you can use two
          useful CImg operations from this menu: denoising
          and enlarging.
          
- 
  Tilt Brightness  
- A  selection  of  tools  for  adjusting  the
          brightness of an image across it’s surface. Useful
          for correcting lighting problems.
          
- 
  Blend  
- Blend  two  objects  together  using  either  a  third
          object to control the blend at each point, or a slider
          to  set  all  points  together.  You  can  blend  almost
          anything with anything.
          One useful version is to use a text image (see Image
           / Make Patterns / Text) to blend between two colours
          (see Colour / New).
           Along  Line   does  a  left/right  or  top/bottom  fade
          between two images.
           
- 
  Overlay  
- Make  a  colour  overlay  of  two  monochrome
          images. Useful with Image / Transform /  for testing
          image superposition.
                                                                                       
                                                                                       
    
- 
Colourize 
- Use  a  colour  image  to  tint  a  monochrome
    image. Useful in conjunction with Image / Transform
    / .
    
- 
Browse 
- Look at either the bits or the bands of an image.
    
- 
Photographic Negative and friends 
- A small selection of
    simple, faintly photoshop-style filters.