HDevelop User's Manual

2.6. VARIABLE WINDOW 55
aspect ratio is always correct. This can lead to black bars at the borders. The color used
to draw the region is always white without further modifications (except zooming).
¯ XLD data is displayed using the coordinate system of the largest image used so far. The
color used for XLD objects is white on black background.
Due to the different ways of displaying objects you have to be aware that the coordinates cannot
be compared. The variable name is positioned below each icon. They are displayed in the
variable window in the order of creation from left to right. If there is not enough space, a
horizontal scrollbar is created, which you can use to scroll the icons.
Clicking on an icon with the mouse will select this icon. This is indicated by the black background
for the icon name. For an activated icon all operators that use the corresponding variable
are marked in the program area with a black rectangle on the left.
Double-clicking with the left mouse button on an icon displays the data in the active graphics
window. If you use images of different sizes in a program, the system uses the following output
strategy for an automatic adaption of the zooming: Every window keeps track of the size of
the most recently displayed image. If you display an image with a different size, the system
modifies the graphics window coordinate system in a way that the image is visible completely
in the graphics window. If a partial zooming has been activated before (see chapter 2.7), it is
going to be suppressed.
Normally, regions, images, and XLDs are represented in variable icons. Besides this there are
three exceptions which are shown by special icons:
¯ Empty variables are displayed as a question mark () icon. You may to write but not read
them, because they do not have any values.
¯ Brackets (℄) are used if a variable is instantiated but does not contain an iconic object
(empty tuple). This may be the case using operators like ×ÐØ ×Ô with “wrong”
specified thresholds or using operator ÑÔØÝ Ó. Such a value might be reasonable if
you want to collect iconic objects in a variable gradually in a loop (ÓÒØ Ó). Here,
an empty tuple is used as starting value for the loop.
¯ A last exception is an empty region. Thisisone region that does not contain any pixels
(points), i.e., the area (number of points) is 0. You must not confuse this case with the
empty tuple, because there the area is not defined. The empty region is symbolized by an
empty set icon ().
2.6.2 Area for Control Data
To the right of the variable name you find their values in the default representation 6 . If you
specify more than one value for one variable (tuple), they are separated by commas and enclosed
by brackets. If the number of values exceeds an upper limit, the output is clipped. This is
indicated by three dots at the end of the tuple. For empty variables, their name and a are
shown in the variable field. An empty tuple is represented by ℄. Both exceptions use the same
symbols as the corresponding cases for the iconic variables.
6 You have to keep in mind that a floating point number without significant fractional part is represented as an
integer (e.g., 1.0 is represented as ½).
HALCON 6.0