Control Types and Constants🔗

All non-iconic data is represented by so called control data (numbers, strings or handles) in HDevelopEVO. The name is derived from their respective functions within HALCON operators where they control the behavior of image processing, for example, thresholds for a segmentation operator. Control parameters in HDevelopEVO may contain arithmetic or logical operations. A control data item can be of one of the following data types: integer, real, string, boolean, and handle.

Control Data Types🔗

`integer`🔗

The data type integer is used under the same syntactical rules as in C. Integer numbers can be input in the standard decimal notation, in hexadecimal by prefixing the number with 0x, and in octal by prefixing the number with 0 (zero).

For example:

4711
-123
0xbeef # (1)!
073421 # (2)!

48879 in decimal notation
30481 in decimal notation

Data items of type integer are converted to their machine-internal representations, that is the C type long (4 or 8 bytes).

The minimum and maximum possible values of an integer depend on whether the 64- or 32-bit version of is used. You can use the operator tuple_number to verify that a value fits into the range of the integer data type. For a reference, see Table 1.

Table 1: Minimum and maximum values of integer
	64-bit	32-bit
Minimum value	−9223372036854775808	−2147483648
Maximum value	9223372036854775807	2147483647

`real`🔗

The data type real is used under the same syntactical rules as in C.

For example:

73.815
0.32214
.56
-17.32e-122
32E19

Data items of type real are converted to their machine-internal representations, that is the C type double (8 bytes).

`string`🔗

A string is a sequence of characters that is enclosed in single quotes ('). Special characters, like the line feed, are represented in the C-like notation, as you can see in Table 2, see the reference of the C language for comparison. You can enter arbitrary characters using the format xnn where nn is a two-digit hexadecimal number, or using the format 0nnn where nnn is a three-digit octal number. Less digits may be used if the string is unambiguous. For example, a line feed may be specified as xa unless the string continues with another hexadecimal digit (0-F).

Table 2: Substitutes for special characters
Meaning	Abbreviation	Notation
line feed	`NL (LF)`	`n`
horizontal tabulator	`HT`	`t`
vertical tabulator	`VT`	`v`
backspace	`BS`	`b`
carriage return	`CR`	`r`
form feed	`FF`	`f`
bell	`BEL`	`a`
backslash	`\`	`\\`
single quote	`'`	`\'`
arbitrary character (hexadecimal)		`\xnn`
arbitrary character (octal)		`\0nnn`

For example: The string Sobel's edge-filter has to be specified as 'Sobel\'s edge-filter'. A Windows directory path can be entered as 'C:\\Programs\\MVTec\\Halcon\\images'

`boolean`🔗

The constants true and false belong to the data type boolean. The value true is internally represented by the number 1 and the value false by 0. This means, that in the expression Val := true the effective value of Val is set to 1. In general, every integer value other than 0 means true. Note that some HALCON operators take logical values for input, for example, set_system. In this case, the HALCON operators expect string constants like 'true' or 'false' rather than the boolean values true or false.

`handle`🔗

Handles are references to complex data structures, for example, a connection to an image acquisition device or a model for shape-based matching.

Special Types🔗

In addition to these general types, there are special constants and the type tuple, which are specific to HALCON or HDevelopEVO, respectively.

constants🔗

For the return value (result state) of an operator, constants exist. The constants can be used together with the operators dev_error_var and dev_set_check. These constants represent the normal return value of an operator, so-called messages. For errors, no constants are available but there are plenty of error numbers internally. For more information, see the Extension Package Programmer’s Manual .

In Table 3, all return messages can be found.

Table 3: Return values for operators
Constant	Meaning	Value
`H_MSG_TRUE`	No error; for tests: `true`	2
`H_MSG_FALSE`	For tests: `false`	3
`H_MSG_VOID`	No result could be computed	4
`H_MSG_FAIL`	Operator did not succeed	5

Additionally, there are constants for the types of control data, see Table 4. These can be compared to the result of a type operation to react to different types of control data, see Type Operations.

Table 4: Type values for control data
Constant	Meaning	Value
`H_TYPE_INT`	integer value	1
`H_TYPE_REAL`	real value	2
`H_TYPE_STRING`	string value	4
`H_TYPE_MIXED`	mixed value	8
`H_TYPE_HANDLE`	handle value	16
`H_TYPE_ANY`	empty tuple	31

tuple🔗

The control types are only used within the generic HDevelopEVO type tuple. A tuple of length 1 is interpreted as an atomic value. A tuple may consist of several data items with different types. The standard representation of a tuple is a listing of its elements surrounded by brackets. This is illustrated in the flowchart in Figure 1.

%%{ init: { 'flowchart': { 'curve': 'stepBefore' } } }%%
graph LR
    A@{ shape: sm-circ } --> OpenBracket
    OpenBracket(["["]) --> Value1["Value"]
    Value1 --> CloseBracket(["]"])
    Value1 --> Comma([","])
    Comma --> Value2["Value"]
    Value2 --> CloseBracket
    Value2 --> Comma
    OpenBracket --> CloseBracket
    CloseBracket --> Z@{shape: sm-circ}

Figure 1. Syntax of tuple constants
“Value” can each have one of the types string, integer, real, boolean, or handle.

[] specifies the empty tuple. A tuple with just one element is to be considered as a special case, because it can either be specified in the tuple notation or as an atomic value: [55] defines the same constant as 55. Examples for tuples are:

4711
0.815
'Text'
[16]
[100.0,100.0,200.0,200.0]
['FileName','Extension']
[4711,0.815,'Hugo']

Control Types and Constants🔗

Control Data Types🔗

integer🔗

real🔗

string🔗

boolean🔗

handle🔗