- 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.
- 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.
They operate on square images only whose sides are a power of two.
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.
- 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
- A small series of faintly photoshop-style filters.