5.8 Tasks
This menu repeats many items from other menus, but
tries to group them by tasks they are useful for, rather than
by function.
5.8.1 Capture
This menu groups operations which are useful in
capturing images, or for the initial processing you might
want to do to an image captured from another program.
-
Capture Video Frame
- This menu item
will currently only work on Linux machines with
a compatible video4linux capture card. See §3.1.1
for notes on how it works.
-
Smooth
- Use this to remove texture from images. It’s
handy in conjunction with Flatfield.
-
Flatfield
- Use this to correct homogeneity. Select
an image of a piece of white (or mid-grey)
card, then select the image to correct, then click
Flatfield. Use Smooth to renmove texture
from the white card if necessary.
You can select a single white and a group of images
to correct a large set in one step
-
White Balance
- Use this to move the white point to
make an area of the image you know to be white,
white. Mark a region on an image, enclosing a
patch you know to be white. Select the region and
the image and click on White Balance.
-
Find Colour Calibration
- Use this to colour calibrate an image. Drag a region enclosing an
image of a Macbeth Color Checker Chart and click
Find Colour Calibration.
-
Apply Colour Calibration
- Use this to apply
the transform calculated by the previous item to
another image. Select the calibration object, select
the RGB image you want calibrated, and click
Apply Colour Calibration.
5.8.2 Mosaic
The items in this menu are discussed in appalling detail in
Chapter 3.
-
One Point
- Join two images left-right or top-bottom
with a simple translation. Mark a point on each
image to be joined (open image view window,
Ctrl-left-click, drag to position), then click on the
mosaic button. The operation performs elaborate
tie-point adjustment, so your selection of a
common feature does not have to be exact.
The Manual versions do not perform automatic
tie-point correction and are useful when joing very
difficult images.
-
Two Point
- Do a join, but allow the right-hand (or
bottom) image to rotate and scale if it will improve
the match. You need to pick two points on each
image.
-
Balance
- Break a mosaic apart, examine average pixel
value in the overlap regions, adjust brightness to
match, and reassemble. This only works for images
which have been produced just by mosaic joins!
If you’ve done anything else to the image since
loading it, the balance will fail with a mysterious
message.
-
Manual Balance
- Adjust the brightness in a set
of masked areas to match. Useful for removing
shadows.
-
Rebuild
- Use this to mosaic up one set of files based
on joins you made in another. Breaks a mosaic part
to component files, performs a string substitution
on the file names, and reassembles.
-
Clone Area
- Select over- or under-exposed pixels
in one image and replace them with the
corresponding pixels from another image. Useful
for removing lead numbers used to identify X-ray
plates.
The function operates on two 8-bit mono images.
Move and resize the region on the first image to
define the area around the white number. Move
the region on the second to overlapping area. A
section of the area on the second image is cloned
and blended into the first image. The amount of
the defined area to be cloned in defined by a slider
within the output image.
5.8.3 Picture Frame
Items useful for mocking up painting frames.
5.8.4 Print
Items useful while preparing an image for printing.
-
Sharpen
- Sharpen an image for printing. This is a
version of Filter / Convolution / Unsharp
Mask tuned for typical inkjet printers.
-
Adjust Tone Curve
- Adjust the reproduction tone
curve in LAB. Most useful for offset work,
especially from transparencies.