// FILE: canvas.h
// written for the course 2172, 1999
//
#if !defined(_CANVAS_H_)
#define _CANVAS_H_

#include "color.h"
#include "pixel.h"
// for the definition of ostream&
#include <iostream.h>

/* canvas class
 *
 * logically an x by y matrix of pixels
 * 
 * internally it has a replica matrix to backup
 * the previous depth
 *
 */
class canvas {
  protected:
    pixel** _bottom; // used for saving the 
                     // image of a lower depth       
    pixel** _top;    // image of current depth
    int x,y;         // resolution

    // The following two constructors are protected
    // so a canvas cannot be assigned to another
    // and it cannot be passed and returned by value
    // (it would be grossly inefficient)
    canvas(const canvas&) {}
    canvas& operator=(const canvas&) { return *this; }

  public:

    // canvas(x,y)
    // constructor, creates an x by y top and bottom grids
    canvas(int,int);

    // C.draw_point(x,y,c,id)
    // assigns the color c to the grid position _top[y][x] or
    // if c == (-1,-1,-1) then _top[y][x] = _bottom[y][x]
    // id designates the identity of figure the pixel belongs to
    void draw_point(int,int,const color&,long);

    // C.fill_area(x,y,id,c2)
    // fills a bounded area
    // the boundary is a pixel with identity id
    void fill_area(int,int,long,const color&);

    // properties
    int width() const;  // returns the width, ie x
    int height() const; // returns the height, ie y

    // C.save_canvas()
    // copies all entries of _top to _bottom
    // (used when jumping depths)
    void save_canvas();

    // properly deallocates the two grids
    virtual ~canvas(); 
   
    // writes an ASCII PPM file to the output stream 
    ostream& dump_text_PPM(ostream&) const;

    // writes a binary PPM file to the output stream
    ostream& dump_binary_PPM(ostream&) const;

    // C.get_color(i,j)
    // returns a copy of the color at _top[i][j]
    color get_color(int,int) const;

    // C.draw_line(x_1,y_1,x_2,y_2,c,id) draws a line
    // from (x_1,y_1) to (x_2,y_2) and performs
    // proper "clipping" and "cropping", in other words
    // it works even if the coordinates are outside the
    // range. color c, id id 
    void draw_line(int,int,int,int,const color&,long);
};

#endif