set_lut — Set “look-up-table” (lut).
set_lut( : : WindowHandle, LookUpTable : )
set_lut sets look-up-table of the device (monitor) displaying
the output window. A look-up-table defines the transformation of a
“gray value” within an image into a gray value or color on the screen.
It describes the screen gray value/color as a combination of red, green and
blue for any image gray value (0..255) (so it is a 'table' to 'look up' the
screen gray value/color for each image gray value: look-up-table).
Transformation into screen-colors is performed in real-time at every
time the screen is displayed new (typically this happens about 60 - 70 times
per second). So it is possible to change the look-up-table to get a new look
of images or regions. Please remind that not all machines support changing
the look-up-table (e.g., monochrome resp. real color).
Look-up-tables within HALCON (and on a machine that supports 256 colors) are divided into three areas:
system area resp. user area,
graphic colors,
image data.
Colors in S descend from applications that were active before starting
HALCON and should not get lost. Graphic colors in G are used for
operators such as disp_region, disp_circle etc.
and are set unique within all look-up-tables. An output in a graphic color
has always got the same (color-)look, even if different look-up-tables are
used. set_color and set_rgb set graphic colors.
Gray values resp. colors in B are used by disp_image to
display an image. They can change according to the current look-up-table.
There exist two exceptions to this concept:
set_gray allows setting of colors of the area B
for operators such as disp_region,
For common monitors only one look-up-table can be loaded per screen.
Whereas set_lut can be activated separately for each window.
There is the following solution for this problem:
It will always be
activated the look-up-table that is assigned to the
“active window” (a window is set into the state “active” by the
window manager).
look-up-table can also be used with true-color displays. In this case the look-up-table will be simulated in software. This means, that the look-up-table will be used each time an image is displayed.
query_lut lists the names of all look-up-tables. They differ
from each other in the area used for gray values. Within this area the
following behavior is defined:
| Value | Description |
|---|---|
| 'default' | Only the two basic colors (generally black and white) are used. |
| Value | Description |
|---|---|
| 'default' | Table proposed by the hardware. |
| Value | Description |
|---|---|
| 'default' | As 'linear'. |
| 'linear' | Linear increasing of gray values from 0 (black) to 255 (white). |
| 'inverse' | Inverse function of 'linear'. |
| 'sqr' | Gray values increase according to square function. |
| 'inv_sqr' | Inverse function of 'sqr'. |
| 'cube' | Gray values increase according to cubic function. |
| 'inv_cube' | Inverse function of 'cube'. |
| 'sqrt' | Gray values increase according to square-root function. |
| 'inv_sqrt' | Inverse Function of 'sqrt'. |
| 'cubic_root' | Gray values increase according to cubic-root function. |
| 'inv_cubic_root' | Inverse Function of 'cubic_root'. |
| Value | Description |
|---|---|
| 'color1' | Linear transition from red via green to blue. |
| 'color2' | Smooth transition from yellow via red, blue to green. |
| 'color3' | Smooth transition from yellow via red, blue, green, red to blue. |
| 'color4' | Smooth transition from yellow via red to blue. |
| 'three' | Displaying the three colors red, green and blue. |
| 'six' | Displaying the six basic colors yellow, red, magenta, blue, cyan and green. |
| 'twelve' | Displaying 12 colors. |
| 'twenty_four' | Displaying 24 colors. |
| 'rainbow' | Displaying the spectral colors from red via green to blue. |
| 'temperature' | Temperature table from black via red, yellow to white. |
| 'change1' | Color changes after every pixel within the table alternating the six basic colors. |
| 'change2' | Fivefold color changes from green via red to blue. |
| 'change3' | Threefold color changes from green via red to blue. |
| 'jet' | Smooth transition from blue via green, yellow to red. |
| 'inverse_jet' | Smooth transition from red via yellow, green to blue. |
The look-up-table LookUpTable to be used in WindowHandle
can be set in the following ways:
Select the look-up-table by setting its name (see query_lut).
Read a look-up-table from a file. Every line of such a file must
contain three numbers in the range of 0 to 255, with the first number
describing the amount of red, the second the amount of green and the third
the amount of blue of the represented display color. The number of lines
can vary. The first line contains information for the first gray value and
the last line for the last value. If there are less lines than gray values,
the available information values are distributed over the whole interval.
If there are more lines than gray values, a number of
(uniformly distributed) lines is ignored.
The file-name must conform to ”LookUpTable.lut”.
Within the parameter the name is specified without file extension.
HALCON will search for the file in the current directory and after that in
a specified directory (see 'lut_dir' in set_system).
Set RGB values directly as a tuple. The number of parameter values must conform to the number of pixels currently used within the look-up-table.
Set a custom value range to be mapped by the look-up-table.
By default, HALCON uses the minimum and maximum gray values
and of an image
(except byte images) and maps these values to 0 and 255 when
applying the look-up-table.
It is possible to override this behavior by passing a tuple to
set_lut in the form [LUT, g_min, g_max] (where
'LUT' is any of the options above).
This feature can be particularly useful when dealing with outliers in a
real image.
The default behavior is reset by using one of the options above without minimum and maximum gray values.
set_lut can only be used with monitors supporting
256 gray levels/colors.
WindowHandle (input_control) window → (handle)
Window handle.
LookUpTable (input_control) filename.read(-array) → (string / integer / real)
Name of look-up-table, values of look-up-table (RGB) or file name.
Default: 'default'
Suggested values: 'default', 'linear', 'inverse', 'sqr', 'inv_sqr', 'cube', 'inv_cube', 'sqrt', 'inv_sqrt', 'cubic_root', 'inv_cubic_root', 'color1', 'color2', 'color3', 'color4', 'three', 'six', 'twelve', 'twenty_four', 'rainbow', 'temperature', 'cyclic_gray', 'cyclic_temperature', 'hsi', 'change1', 'change2', 'change3', 'jet', 'jet_inverse'
File extension:
.lut
read_image(Image,'monkey') query_lut(WindowHandle,LUTs) for i := 0 to |LUTs|-1 by 1 set_lut(WindowHandle,LUTs[i]) fwrite_string(FileHandle, ['current table ',LUTs[i]]) fnew_line(FileHandle) get_mbutton(WindowHandle,_,_,_) endfor
set_lut returns 2 (
H_MSG_TRUE)
if the hardware supports a look-up-table
and the parameter is correct. Otherwise an exception is raised.
get_lut,
query_lut,
set_color,
set_rgb,
set_hsi,
write_lut
Foundation