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### 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.

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