This chapter contains operators regarding the handling of images.
In order to understand the different types of images you can process in HALCON, the three components of an image (pixels, channels and domain) are explained in the following paragraphs.
In HALCON pixels can be used in order to represent information of various
kinds. Therefore different pixel types are distinguished.
The following table lists the different pixel types and the corresponding
standard image types for images. Note that this list is not exclusive (e.g.,
a gray value image can be of multiple other image types as well).
You can convert the image type using
.
convert_image_type
Pixel Type | Standard Image Type |
---|---|
Gray Values | byte, uint2 |
Difference | int1, int2 |
2D Histogram | int4
|
Edge Directions | direction |
Derivatives | real |
Fourier Transform | complex |
Hue Values | cyclic |
Vector Field | vector_field
|
Note that the image type vector_field
can be specified further
by using vector_field_absolute
or vector_field_relative
.
There is also the image type int8
(64 bits with sign), which is
only available on 64 bit systems.
Further information on the different pixel types is given below.
Gray images are of type byte
(8 bits without sign) or
uint2
(16 bits without sign) and consist of pixels usually
representing local intensities of light on a sensor.
In order to show the differences between two images e.g., the image
types int1
(8 bits with sign) or int2
(16 bits with
sign) are well suited.
(1) | (2) | (3) |
To examine image features based on the occurrence of gray values in
two images you can use a 2D histogram, which is of type int4
(32 bits with sign). Thereby, the axes of the 2D histogram each
represent the gray values of an input image. The gray values of
corresponding pixels in the input images are registered in the 2D
histogram accordingly. The higher the frequency of a specific
combination of gray values, the higher the gray value in the output
image (see also
).
histo_2dim
(1) | (2) | (3) |
To represent the orientation of the edge gradient, the image type
direction
(8 bits without sign) is available.
(1) | (2) |
For images of type direction
an edge direction of x degrees
in mathematically positive sense and with respect to the horizontal
axis is stored as x / 2 in the edge direction image (resulting in
gray values from 0 to 179).
Points with edge amplitude 0 are assigned the edge direction 255
(undefined direction).