set_lut — Set “look-up-table” (lut).
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 diposed into three areas:
system area resp. user area,
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_fix that allows modification of graphic colors.
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 truecolor 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.
WindowsNT specific: if the graphiccard is used in mode different from truecolor, you must display the image after setting the look-up-taple.
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 behaviour is defined:
gray value tables (1-7 image levels)
Only the two basic colors (generally black and white) are used.
color tables (Real color, static gray value steps)
Table proposed by the hardware.
gray value tables (256 colors)
Linear increasing of gray values from 0 (black) to 255 (white).
Inverse function of 'linear'.
Gray values increase according to square function.
Inverse function of 'sqr'.
Gray values increase according to cubic function.
Inverse function of 'cube'.
Gray values increase according to square-root function.
Inverse Function of 'sqrt'.
Gray values increase according to cubic-root function.
Inverse Function of 'cubic_root'.
color tables (256 colors)
Linear transition from red via green to blue.
Smooth transition from yellow via red, blue to green.
Smooth transition from yellow via red, blue, green, red to blue.
Smooth transition from yellow via red to blue.
Displaying the three colors red, green and blue.
Displaying the six basic colors yellow, red, magenta, blue, cyan and green.
Displaying 12 colors.
Displaying 24 colors.
Displaying the spectral colors from red via green to blue.
Temperature table from black via red, yellow to white.
Color changement after every pixel within the table alternating the six basic colors.
Fivefold color changement from green via red to blue.
Threefold color changement from green via red to blue.
A look-up-table can be read 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 set_system(::'lut_dir',<Pfad>:) ). It is also possible to call set_lut with a tuple of RGB-Values. These will be set directly. The number of parameter values must conform to the number of pixels currently used within the look-up-table.
set_lut can only be used with monitors supporting 256 gray levels/colors.
Name of look-up-table, values of look-up-table (RGB) or file name.
Default value: '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'
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_fix, set_color, set_rgb, set_hsi, write_lut