图形编程（数值微分DDA）

#include <iostream>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
using namespace std;

int searchXY(int y,int x,int H,int W)
{
    return W*y+x;
}

int Min(int a,int b)
{
    return a < b? a :b;
}

int Max(int a,int b)
{
    return a> b? a:b;
}

void main()
{
    double x1=-0.75,y1=-0.5;

    double x2=0.6, y2=0.4;

    int H=312,W=248;
    double *pix=new double[H*W];

    double X1=x1*W/2;
    double Y1=y1*H/2;

    double X2=x2*W/2;
    double Y2=y2*H/2;

    double k=0;

    int xMin=Min(X1,X2);
    int xMax=Max(X1,X2);
    k=(Y2-Y1)/(X2-X1);
    for (int x=xMin;x<xMax;x++)
    {
        double b=Y1-k*X1;
        int y=k*x+b;    
        pix[searchXY(y+H/2,x+W/2,H,W)]=255;
    }
    
    int yMin=Min(Y1,Y2);
    int yMax=Max(Y1,Y2);
    k=(X2-X1)/(Y2-Y1);
    for (int y=yMin;y<yMax;y++)
    {
        double b=X1-k*Y1;
        int x=k*y+b;    
        pix[searchXY(y+H/2,x+W/2,H,W)]=255;
    }
    
    FILE *f=fopen("img.ppm","w");
    fprintf(f,"P3\n%d %d\n%d\n",W,H,255);

    for (int i=0;i<W*H;i++)
        fprintf(f,"%d %d %d\n",int(pix[i]),int(pix[i]),int(pix[i]));
    
    fclose(f);
    delete[] pix;
}