Help With Rectangle/Ellipse Image Drawing

[louiesluck]

Hello,

I currently need to write a program for my class that continuously requires me to give the user 3 choices of either drawing a rectangle, an ellipse, or to save the previous images and exit the loop and program.

if rectangle or ellipse is selected, the user is then prompted to input 4 dimensions that aid in drawing the selected image in a maximum box of 256, i suppose pixels?.

I am having trouble writing the four loops for my function calls regarding either shape.

  #include <iostream>
//contains constant SIZE and other necessary functions
//SIZE is in a "bmplib.h", a file the professor provides to us to call
#include "bmplib.h"
using namespace std;

// global variable. bad style but ok for this lab
unsigned char image[SIZE][SIZE];

//forward calling of function
void draw_rectangle(int, int, int, int);
void draw_ellipse(int, int, int, int);


int main()
{
	
	//populates 2D array
   for (int i=0; i < SIZE; i++)
   	{
      for (int j=0; j < SIZE; j++)
	   	{
         image[i][j] = 255;
         
    	}
 	}
    
    //Variable Decalartions
	int a, top, left, height, width, cy, cx;
	
	cout << "To draw a rectangle, enter: 0 top left height width" << endl;
	cout << "To draw an ellipse, enter: 1 cy cx height width" << endl;
	cout << "To save your drawing as 'output.bmp' and quit enter: 2 " << endl;
	cin >> a;
	

		//Does loop continuously until exit condition is inputted
		while(a!=2)
		{
			//enters rectangle 
			if(a == 0)
			{
				cin >> top >> left >> height >> width;
				draw_rectangle(top,left,height,width);
			}
			else
			//enters ellipse
			if( a == 1)
			{
				cin >> cy >> cx >> height >> width;
				draw_ellipse(int cy, int cx, int height, int width);
			}
			//asks user for new selection
			cout << "To draw a rectangle, enter: 0 top left height width" << endl;
			cout << "To draw an ellipse, enter: 1 cy cx height width" << endl;
			cout << "To save your drawing as 'output.bmp' and quit enter: 2 " << endl;
			cin >> a;
		
		}
			//after exit condition is entered, saves image and prints 
			writeGSBMP("cross.bmp", image);


	
//end program
return 0;
}


// Fill in this function:
void draw_rectangle(int top, int left, int height, int width)
{
	
}

// Fill in this function:
void draw_ellipse(int cy, int cx, int height, int width) {

}

Apparently the program is to also print what it can in the allocated draw space even if someone enters a dimension outside of it and it does not wrap around..whatever that means :(

Any help or suggestions would be greatly appreciated!

Louie

[H00G0]

Assuming your 2D array image is what you're supposed to draw, it should be passed as an argument to your functions draw_rectangle and draw_ellipse.

Why are you initialising all of your array's values to 255, they are chars, why not set them to whitespaces ' '?

What is it that you're having trouble with, is it the logic behind drawing to your 2D array?

[lastchance]

#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;

const bool FILL   = true ;    // fill figures or not?
const int  SIZE   = 60   ;    // change to 256 when you want
const char MARKER = '*'  ;

unsigned char image[SIZE][SIZE];

// Forward declarations
int iround( double x );
void column( int j, int i1, int i2, bool solid );
void drawEllipse( int cy, int cx, int height, int width );
void drawRectangle( int top, int left, int height, int width );
void plot();
void clear();


int main()
{
   int answer, top, left, height, width, cy, cx;
        
   while( true )
   {
      clear();

      cout << "To draw a rectangle, enter: 1 top left height width\n";
      cout << "To draw an ellipse, enter: 2 cy cx height width\n";
      cout << "Anything else will quit.\n";
      cin >> answer;
           
      switch( answer )
      {
         case 1:
         {
            cin >> top >> left >> height >> width;
            drawRectangle( top, left, height, width );
            plot();
            break;
         }
         case 2:
         {
            cin >> cy >> cx >> height >> width;
            drawEllipse( cy, cx, height, width );
            plot();
            break;
         }                  
         default:
         {
            return 0;
         }
      }                                                                                                                                 
   }                                                                                                                                 
}

//==================

int iround( double x )
{
   int i = ( x >= 0 ? x + 0.5 : x - 0.5 );
   return i;
}

//==================

void column( int j, int i1, int i2, bool solid )
{
   if ( j < 0 || j >= SIZE ) return;                       // clip left and right
   if ( i1 >= 0 && i1 < SIZE ) image[i1][j] = MARKER;      // clip top
   if ( i2 >= 0 && i2 < SIZE ) image[i2][j] = MARKER;      // clip bottom
   if ( solid )
   {
      for ( int i = max( i1 + 1, 0 ); i <= min( i2 - 1, SIZE - 1 ); i++ ) image[i][j] = MARKER;
   }
}

//==================

void drawEllipse( int cy, int cx, int height, int width )
{
   double a = width / 2.0, b = height / 2.0;    // ellipse semi-axes
   for ( int x = iround( cx - a ); x <= iround( cx + a ); x++ )
   {
      double xrel = ( x - cx ) / a;
      double yrel = sqrt( 1.0 - xrel * xrel );
      int y1 = iround( cy - b * yrel );
      int y2 = iround( cy + b * yrel );
      column( x, y1, y2, FILL );
    }
}

//==================

void drawRectangle( int top, int left, int height, int width )
{
   int y1 = top, y2 = top + height;
   column( left        , y1, y2, true );
   column( left + width, y1, y2, true );
   for ( int x = left + 1; x <= left + width - 1; x++ ) column( x, y1, y2, FILL );
}

//==================

void plot()
{
   for ( int i = 0; i < SIZE; i++ )
   {
      for (int j = 0; j < SIZE; j++ ) cout << image[i][j];
      cout << '\n';
   }
}

//==================

void clear()
{
   for ( int i = 0; i < SIZE; i++ )
   {
      for (int j = 0; j < SIZE; j++ ) image[i][j] = ' ';
   }
}

//================== 

To draw a rectangle, enter: 1 top left height width
To draw an ellipse, enter: 2 cy cx height width
Anything else will quit.
1 5 5 10 30
                                                            
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
     *******************************                        
                                                            
                                                            


                                                            
To draw a rectangle, enter: 1 top left height width
To draw an ellipse, enter: 2 cy cx height width
Anything else will quit.
2 30 30 10 40



                      *****************                     
                *****************************               
             ***********************************            
           ***************************************          
           ***************************************          
          *****************************************         
           ***************************************          
           ***************************************          
             ***********************************            
                *****************************               
                      *****************                     



To draw a rectangle, enter: 1 top left height width
To draw an ellipse, enter: 2 cy cx height width
Anything else will quit.
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