1. int rows, cols;
   int[][] data; // this is the 2D-array, where the data shall be stored
   
   void setup() {
     String[] lines = loadStrings("data.csv"); // lets assume, you have comma-seperated values
     rows = lines.length; 
     cols = split(lines[0], ',').length;
   
     // initialize you data-array
     data = new int[cols][rows]; 
   
     // parse you data-file
     for (int row =0; row<lines.length; row++) {
       // split current line by ','
       String[] values = split(lines[row], ',');
       // loop through the values of that line
       for (int col =0; col<values.length; col++) {
         // store value in your array
         data[col][row] = int(values[col]);
       }
     }
   }

The code to draw this to an image would be the same.

1. // Draw points
   for (int i = 0; i < cols; i++) {
     for (int j = 0; j < rows; j++) {
       stroke(data[i][j]);
       point(i, j);
     }
   }