PredatorPrey_step12 - gama-platform/gama GitHub Wiki
This 12th step illustrates how to load an image file and to use it to initialize a grid.
- Building of the initial environment (
food
andfood_prod
of the cells) from an image file.
We add a new global variable to store the image data:
file map_init <- image_file("../includes/data/raster_map.png");
You have to copy it in your project folder: includes/data/
.
In order to have a more complex environment, we want to use this image as the initialization of the environment. The food level available in a vegetation_cell
will be based on the green level of the corresponding pixel in the image. You will be able to use such a process to represent an existing real environment in your model.
We modify the global init
of the model in order to cast the image file in a matrix.
First of all, when the variable map_init
is defined from an image file (or a csv file), it can be manipulated directly as a matrix, with the dimensions of the image (here it is a 50x50 image, which matches with the grid size). In the case we need to resize the image, we can use the file as_matrix {nb_cols, nb_lines}
operator that allows converting a file (image, csv) to a matrix composed of nb_cols
columns and nb_lines
lines.
Concerning the manipulation of a matrix, it is possible to obtain the element [i,j] of a matrix by using my_matrix [i,j]
.
A grid can be view as a spatial matrix: each cell of a grid has two built-in variables grid_x
and grid_y
that represent the column and line indexes of the cell.
init {
create prey number: nb_preys_init ;
create predator number: nb_predators_init ;
ask vegetation_cell {
color <- rgb (map_init at {grid_x,grid_y}) ;
food <- 1 - (((color as list) at 0) / 255) ;
food_prod <- food / 100 ;
}
}
https://github.com/gama-platform/gama.old/blob/GAMA_1.9.2/msi.gama.models/models/Tutorials/Predator%20Prey/models/Model%2012.gaml