Source: contour_demo.f90
Comprehensive contour plotting examples: line contours, filled contours, custom levels, colormaps.
contour_demo.f90 - Source codeoutput/example/fortran/contour_demo/make example ARGS="contour_demo"

ASCII output:
Filled Contour Demo (plasma)
+--------------------------------------------------------------------------------+
| 2.4 |
| | |
| 1.6 |
| | |
| | |
| | |
| | |
| |.........-----====++++++++++***+++++++++++++***++++++++++====-----..........- |
| |.......------====+++++++++========-------========+++++++++====------......... |
| |...----====+++++++====--...........................--====+++++++====----..... |
| 0.8--===++++++===--.......................................--===++++++===----.. |
| |===+++++++===-...............................................-===+++++++===-- |
| |==+++++++==-...............--==++++*****++++==--...............-==+++++++==== |
| |.0++++++==--............-=++*@@@@@**+++**@@@@@*++=-............--==++++++++== |
| |++++++++==--............-=++*@@@@@**+++**@@@@@*++=-............--==++++++++== |
| |==+++++++==-...............--==++++*****++++==--...............-==+++++++==== |
| |===+++++++===-...............................................-===+++++++===-- |
| |----===++++++===--.......................................--===++++++===----.. |
| -0.8----====+++++++====--...........................--====+++++++====----..... |
| |.....----===++++++++++++++========-------========++++++++++++++===----....... |
| | |
| |1.6 |
| | |
| | |
| | |
| | - - - - - - - - - - - - - - - - - - - - - - - - - |
| -2.4 -2.4 -1.6 -0.8 0.0 0.8 1.6 2.4 |
+--------------------------------------------------------------------------------+
x
y

ASCII output:
2D Gaussian Function
+--------------------------------------------------------------------------------+
| |
| | |
| 2.4 |
| | |
| | |
| | |
| |.6 |
| | |
| | |
| | |
| |.8 |
| | |
| | --------------------- |
| | ------------------------------- |
| | -- ----------------------------- -- |
| 0.0 -- - - - -- -- -- -- - - - -- |
| | -- ----------------------------- -- |
| | ------------------------------- |
| |0.8 --------------------- |
| | |
| | |
| | |
| |1.6 |
| | |
| | |
| | |
| | |
| | |
| | - - - - - - - - - - - - - - - - - - - - - - - - - |
| -2.4 -2.4 -1.6 -0.8 0.0 0.8 1.6 2.4 |
+--------------------------------------------------------------------------------+
x
y

ASCII output:
Mixed Plot: Contour + Line
+--------------------------------------------------------------------------------+
| |
| | |
| 2.4 |
| | |
| | |
| | |
| |.6 |
| | |
| |- -- --- --- -- -- |
| |------------------- --------------------- |
| |.8----------------------------------- --------------------------------------- |
| | ---- ----- ------ ----------- --- ----------- ------ ----- ---- |
| | --- ----- ------- ----------------- ------- ----- --- |
| | --- ---- ------## ## # # ## ##------ ---- --- |
| | -- --- # ### #------ -----# ### # --- -- |
| 0.0 # # # -# # # -# ------- #- # # #- # # # # # |
| | -- --- ----- ----- --- -- |
| | --- ---- ------ ------ ---- --- |
| |0.8 --- ----- ------- ----------------- ------- ----- --- |
| | ---- ----- ------ ----------- --- ----------- ------ ----- ---- |
| |------------------------------------- --------------------------------------- |
| |------------------- --------------------- |
| |1.6-- --- --- -- -- |
| | |
| | |
| | |
| | |
| | |
| | - - - - - - - - - - - - - - - - - - - - - - - - - |
| -2.4 -2.4 -1.6 -0.8 0.0 0.8 1.6 2.4 |
+--------------------------------------------------------------------------------+
x
y

ASCII output:
Ripple Function - Coolwarm Colormap
+--------------------------------------------------------------------------------+
| 2.0 |
| | |
| 1.5 |
| | |
| | |
| | |
| | |
| 1.0++######%%%%#####++++++=========================++++++#####%%%%######++++++ |
| |.5#%%%###++++======---------===================---------======++++###%%%##### |
| |%###+++=====---------------=====================---------------=====+++###%%% |
| |#++=====---------=====++++###%%%%%%%###%%%%%%%###++++=====---------=====++### |
| |++====------====+++##%%##+++-------+++++-------+++##%%##+++====------====+++# |
| 0.0====----====++##%%##++---::::---+++++++---::::---++##%%##++====----====+++# |
| |++====------====+++##%%##+++-------+++++-------+++##%%##+++====------====+++# |
| |#++=====---------=====++++###%%%%%%%###%%%%%%%###++++=====---------=====++### |
| |%###+++=====---------------=====================---------------=====+++###%%% |
| |###%%%###++++======---------===================---------======++++###%%%##### |
| -0.5+######%%%%#####++++++=========================++++++#####%%%%######++++++ |
| | |
| | |
| |1.5 |
| | |
| | - - - - - - - - - - - - - - - - - |
| -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 |
+--------------------------------------------------------------------------------+
x
y

ASCII output:
Ripple Function - Inferno Colormap
+--------------------------------------------------------------------------------+
| 2.0 |
| | |
| 1.5 |
| | |
| | |
| | |
| | |
| 1.0**======----:::::....... .......:::::----======****** |
| |.5=---:::.....::::....... .......::::.....:::---===== |
| |-:::......... .....:::-------=-------:::..... .........:::--- |
| |:....... ...::.....:::-------===-------:::.....::... .......::: |
| |.... ......::--==***@@@@@@@*****@@@@@@@***==--::...... .....: |
| 0.0. ...::--==**@@@@@@@@@@*******@@@@@@@@@@**==--::... ....: |
| |.... ......::--==***@@@@@@@*****@@@@@@@***==--::...... .....: |
| |:....... ...::.....:::-------===-------:::.....::... .......::: |
| |-:::......... .....:::-------=-------:::..... .........:::--- |
| |===---:::.....::::....... .......::::.....:::---===== |
| -0.5*======----:::::....... .......:::::----======****** |
| | |
| | |
| |1.5 |
| | |
| | - - - - - - - - - - - - - - - - - |
| -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 |
+--------------------------------------------------------------------------------+
x
y

ASCII output:
Ripple Function - Jet Colormap
+--------------------------------------------------------------------------------+
| 2.0 |
| | |
| 1.5 |
| | |
| | |
| | |
| | |
| 1.0::++++++%%%%#####******-------------------------******#####%%%%++++++:::::: |
| |.5+%%%###****-------****---------------------------****-------****###%%%+++++ |
| |%###***----------------***-----------------------***----------------***###%%% |
| |#**-------------------****###%%%%%%%+++%%%%%%%###****-------------------**### |
| |**------ ------***##%%++:::::::::::::::::::::::::++%%##***------ ------***# |
| 0.0----- -----**##%%++:::::....:::::::::::::....:::::++%%##**----- -----***# |
| |**------ ------***##%%++:::::::::::::::::::::::::++%%##***------ ------***# |
| |#**-------------------****###%%%%%%%+++%%%%%%%###****-------------------**### |
| |%###***----------------***-----------------------***----------------***###%%% |
| |+++%%%###****-------****---------------------------****-------****###%%%+++++ |
| -0.5:++++++%%%%#####******-------------------------******#####%%%%++++++:::::: |
| | |
| | |
| |1.5 |
| | |
| | - - - - - - - - - - - - - - - - - |
| -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 |
+--------------------------------------------------------------------------------+
x
y