CROPPING AND MEASURING WITH A SINGLE LENS

RECADRAGE ET MESURE AVEC UN SEUL OBJECTIF

Description

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Cropping and Measuring with a Single Lens
Background
The "Applications of Multiple Lenses in Detail-In-Context Data Presentations"
documents the ideas of cropping and measuring with multiple lenses. In this
previous
application, the lenses are defined first, then the crop or measure tool is
selected and crop
is performed through the lens. Or, the lens simply acts as a carrier for the
tool. That is,
the center of the lens follows the tool around. Since the Line that defines
the crop is in the
focus of the lens where a better resolution of the image can be seen, the
cropping
operation is far more accurate.
This documents defines the same process as the previous document, however in
this case,
only one lens used. The lens may be a carrier for the tool, or the lens may
actually be the
tool itself.
Description of cropping with single lens
One of the most common, yet troublesome, tasks is to precisely crop areas of
interest.
Generally the user needs to pinpoint at least two points to define a rectangle
(top left and
bottom right), or more points to define an arbitrary polygonal shape. Zooming
into the
image prevents other important points from being visible. However, by using a
lens, this
task becomes trivial. This section describes the process of cropping with a
lens.
Details
Figure 1 illustrates the process of cropping a rectangle with a single lens.
The user first
selects the cropping tool (which is associated with a lens) and clicks on a
starting point.

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Figure 1. Selecting a point at pixel level and starting to crop a rectangle
with a lens.
Then the user drags the lens the next location to complete the rectangle. The
lens follows
as shown in Figure 2. The dotted lines are drawn as the lens move diagonally
across the
page. The rectangle defines the area to be cropped.
Figure 2. Cropping an area with a lens.
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Variations
1. The lens simply follows the crop tool and act as a carrier for the tool.
2. The tool may defined to be associated with a lens, making the lens appear
to be
the tool
3. The user may also use the lens to crop an arbitrary shape. This idea can be
extrapolated from Figure 3. The lines that represent distance may be lines
that
define where the image may be cropped.
4. 'The cropping tool may or may not be visible in the lens. In Figure 1 and
2, the
tool is not visible. In Figure 3, the tool is visible.
Description of measuring with single lens
Measuring distances between points may be achieved with better accuracy
through a lens.
Figure 3 show an example of making measurements with a single lens.
a) The starting point: the measure tool is attached to the center of the lens.
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b) The first distance segment has been created. The line, in this example has
been is
XORed with the background image.
c) Two line segments can be seen. The lens continues to follow the tool.
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Figure 3 Using a lens to take measurements
Figure 3 may used to show how a lens may used to crop an image. That is the
lines
created as the lens moves from point to point may be the lines that define
where the
image is to be cropped.
Variations
1. The lens may be attached to the center of the tool
2. The measure tool may be defined with lens