?? demo8_2.cpp
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// DEMO8_2.CPP 8-bit line clipping demo
// INCLUDES ///////////////////////////////////////////////
#define WIN32_LEAN_AND_MEAN // just say no to MFC
#define INITGUID
#include <windows.h> // include important windows stuff
#include <windowsx.h>
#include <mmsystem.h>
#include <iostream.h> // include important C/C++ stuff
#include <conio.h>
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include <math.h>
#include <io.h>
#include <fcntl.h>
#include <ddraw.h> // include directdraw
// DEFINES ////////////////////////////////////////////////
// defines for windows
#define WINDOW_CLASS_NAME "WINCLASS1"
// default screen size
#define SCREEN_WIDTH 640 // size of screen
#define SCREEN_HEIGHT 480
#define SCREEN_BPP 8 // bits per pixel
#define BITMAP_ID 0x4D42 // universal id for a bitmap
#define MAX_COLORS_PALETTE 256
// TYPES //////////////////////////////////////////////////////
// basic unsigned types
typedef unsigned short USHORT;
typedef unsigned short WORD;
typedef unsigned char UCHAR;
typedef unsigned char BYTE;
// PROTOTYPES //////////////////////////////////////////////
int DDraw_Fill_Surface(LPDIRECTDRAWSURFACE7 lpdds,int color);
int Draw_Line(int x0, int y0, int x1, int y1, UCHAR color, UCHAR *vb_start, int lpitch);
int Draw_Clip_Line(int x0,int y0, int x1, int y1,UCHAR color,
UCHAR *dest_buffer, int lpitch);
int Clip_Line(int &x1,int &y1,int &x2, int &y2);
// MACROS /////////////////////////////////////////////////
// tests if a key is up or down
#define KEYDOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)
#define KEYUP(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)
// initializes a direct draw struct
#define DDRAW_INIT_STRUCT(ddstruct) { memset(&ddstruct,0,sizeof(ddstruct)); ddstruct.dwSize=sizeof(ddstruct); }
// GLOBALS ////////////////////////////////////////////////
HWND main_window_handle = NULL; // globally track main window
int window_closed = 0; // tracks if window is closed
HINSTANCE hinstance_app = NULL; // globally track hinstance
// directdraw stuff
LPDIRECTDRAW7 lpdd = NULL; // dd object
LPDIRECTDRAWSURFACE7 lpddsprimary = NULL; // dd primary surface
LPDIRECTDRAWSURFACE7 lpddsback = NULL; // dd back surface
LPDIRECTDRAWPALETTE lpddpal = NULL; // a pointer to the created dd palette
LPDIRECTDRAWCLIPPER lpddclipper = NULL; // dd clipper
PALETTEENTRY palette[256]; // color palette
PALETTEENTRY save_palette[256]; // used to save palettes
DDSURFACEDESC2 ddsd; // a direct draw surface description struct
DDBLTFX ddbltfx; // used to fill
DDSCAPS2 ddscaps; // a direct draw surface capabilities struct
HRESULT ddrval; // result back from dd calls
DWORD start_clock_count = 0; // used for timing
// global clipping region
int min_clip_x = ((SCREEN_WIDTH/2) - 100), // clipping rectangle
max_clip_x = ((SCREEN_WIDTH/2) + 100),
min_clip_y = ((SCREEN_HEIGHT/2) - 100),
max_clip_y = ((SCREEN_HEIGHT/2) + 100);
char buffer[80]; // general printing buffer
// FUNCTIONS ////////////////////////////////////////////////
inline int Draw_Pixel(int x, int y,int color,
UCHAR *video_buffer, int lpitch)
{
// this function plots a single pixel at x,y with color
video_buffer[x + y*lpitch] = color;
// return success
return(1);
} // end Draw_Pixel
/////////////////////////////////////////////////////////////
int DDraw_Fill_Surface(LPDIRECTDRAWSURFACE7 lpdds,int color)
{
DDBLTFX ddbltfx; // this contains the DDBLTFX structure
// clear out the structure and set the size field
DDRAW_INIT_STRUCT(ddbltfx);
// set the dwfillcolor field to the desired color
ddbltfx.dwFillColor = color;
// ready to blt to surface
lpdds->Blt(NULL, // ptr to dest rectangle
NULL, // ptr to source surface, NA
NULL, // ptr to source rectangle, NA
DDBLT_COLORFILL | DDBLT_WAIT, // fill and wait
&ddbltfx); // ptr to DDBLTFX structure
// return success
return(1);
} // end DDraw_Fill_Surface
///////////////////////////////////////////////////////////////
int Draw_Clip_Line(int x0,int y0, int x1, int y1,UCHAR color,
UCHAR *dest_buffer, int lpitch)
{
// this helper function draws a clipped line
int cxs, cys,
cxe, cye;
// clip and draw each line
cxs = x0;
cys = y0;
cxe = x1;
cye = y1;
// clip the line
if (Clip_Line(cxs,cys,cxe,cye))
Draw_Line(cxs, cys, cxe,cye,color,dest_buffer,lpitch);
// return success
return(1);
} // end Draw_Clip_Line
///////////////////////////////////////////////////////////
int Clip_Line(int &x1,int &y1,int &x2, int &y2)
{
// this function clips the sent line using the globally defined clipping
// region
// internal clipping codes
#define CLIP_CODE_C 0x0000
#define CLIP_CODE_N 0x0008
#define CLIP_CODE_S 0x0004
#define CLIP_CODE_E 0x0002
#define CLIP_CODE_W 0x0001
#define CLIP_CODE_NE 0x000a
#define CLIP_CODE_SE 0x0006
#define CLIP_CODE_NW 0x0009
#define CLIP_CODE_SW 0x0005
int xc1=x1,
yc1=y1,
xc2=x2,
yc2=y2;
int p1_code=0,
p2_code=0;
// determine codes for p1 and p2
if (y1 < min_clip_y)
p1_code|=CLIP_CODE_N;
else
if (y1 > max_clip_y)
p1_code|=CLIP_CODE_S;
if (x1 < min_clip_x)
p1_code|=CLIP_CODE_W;
else
if (x1 > max_clip_x)
p1_code|=CLIP_CODE_E;
if (y2 < min_clip_y)
p2_code|=CLIP_CODE_N;
else
if (y2 > max_clip_y)
p2_code|=CLIP_CODE_S;
if (x2 < min_clip_x)
p2_code|=CLIP_CODE_W;
else
if (x2 > max_clip_x)
p2_code|=CLIP_CODE_E;
// try and trivially reject
if ((p1_code & p2_code))
return(0);
// test for totally visible, if so leave points untouched
if (p1_code==0 && p2_code==0)
return(1);
// determine end clip point for p1
switch(p1_code)
{
case CLIP_CODE_C: break;
case CLIP_CODE_N:
{
yc1 = min_clip_y;
xc1 = x1 + 0.5+(min_clip_y-y1)*(x2-x1)/(y2-y1);
} break;
case CLIP_CODE_S:
{
yc1 = max_clip_y;
xc1 = x1 + 0.5+(max_clip_y-y1)*(x2-x1)/(y2-y1);
} break;
case CLIP_CODE_W:
{
xc1 = min_clip_x;
yc1 = y1 + 0.5+(min_clip_x-x1)*(y2-y1)/(x2-x1);
} break;
case CLIP_CODE_E:
{
xc1 = max_clip_x;
yc1 = y1 + 0.5+(max_clip_x-x1)*(y2-y1)/(x2-x1);
} break;
// these cases are more complex, must compute 2 intersections
case CLIP_CODE_NE:
{
// north hline intersection
yc1 = min_clip_y;
xc1 = x1 + 0.5+(min_clip_y-y1)*(x2-x1)/(y2-y1);
// test if intersection is valid, of so then done, else compute next
if (xc1 < min_clip_x || xc1 > max_clip_x)
{
// east vline intersection
xc1 = max_clip_x;
yc1 = y1 + 0.5+(max_clip_x-x1)*(y2-y1)/(x2-x1);
} // end if
} break;
case CLIP_CODE_SE:
{
// south hline intersection
yc1 = max_clip_y;
xc1 = x1 + 0.5+(max_clip_y-y1)*(x2-x1)/(y2-y1);
// test if intersection is valid, of so then done, else compute next
if (xc1 < min_clip_x || xc1 > max_clip_x)
{
// east vline intersection
xc1 = max_clip_x;
yc1 = y1 + 0.5+(max_clip_x-x1)*(y2-y1)/(x2-x1);
} // end if
} break;
case CLIP_CODE_NW:
{
// north hline intersection
yc1 = min_clip_y;
xc1 = x1 + 0.5+(min_clip_y-y1)*(x2-x1)/(y2-y1);
// test if intersection is valid, of so then done, else compute next
if (xc1 < min_clip_x || xc1 > max_clip_x)
{
xc1 = min_clip_x;
yc1 = y1 + 0.5+(min_clip_x-x1)*(y2-y1)/(x2-x1);
} // end if
} break;
case CLIP_CODE_SW:
{
// south hline intersection
yc1 = max_clip_y;
xc1 = x1 + 0.5+(max_clip_y-y1)*(x2-x1)/(y2-y1);
// test if intersection is valid, of so then done, else compute next
if (xc1 < min_clip_x || xc1 > max_clip_x)
{
xc1 = min_clip_x;
yc1 = y1 + 0.5+(min_clip_x-x1)*(y2-y1)/(x2-x1);
} // end if
} break;
default:break;
} // end switch
// determine clip point for p2
switch(p2_code)
{
case CLIP_CODE_C: break;
case CLIP_CODE_N:
{
yc2 = min_clip_y;
xc2 = x2 + (min_clip_y-y2)*(x1-x2)/(y1-y2);
} break;
case CLIP_CODE_S:
{
yc2 = max_clip_y;
xc2 = x2 + (max_clip_y-y2)*(x1-x2)/(y1-y2);
} break;
case CLIP_CODE_W:
{
xc2 = min_clip_x;
yc2 = y2 + (min_clip_x-x2)*(y1-y2)/(x1-x2);
} break;
case CLIP_CODE_E:
{
xc2 = max_clip_x;
yc2 = y2 + (max_clip_x-x2)*(y1-y2)/(x1-x2);
} break;
// these cases are more complex, must compute 2 intersections
case CLIP_CODE_NE:
{
// north hline intersection
yc2 = min_clip_y;
xc2 = x2 + 0.5+(min_clip_y-y2)*(x1-x2)/(y1-y2);
// test if intersection is valid, of so then done, else compute next
if (xc2 < min_clip_x || xc2 > max_clip_x)
{
// east vline intersection
xc2 = max_clip_x;
yc2 = y2 + 0.5+(max_clip_x-x2)*(y1-y2)/(x1-x2);
} // end if
} break;
case CLIP_CODE_SE:
{
// south hline intersection
yc2 = max_clip_y;
xc2 = x2 + 0.5+(max_clip_y-y2)*(x1-x2)/(y1-y2);
// test if intersection is valid, of so then done, else compute next
if (xc2 < min_clip_x || xc2 > max_clip_x)
{
// east vline intersection
xc2 = max_clip_x;
yc2 = y2 + 0.5+(max_clip_x-x2)*(y1-y2)/(x1-x2);
} // end if
} break;
case CLIP_CODE_NW:
{
// north hline intersection
yc2 = min_clip_y;
xc2 = x2 + 0.5+(min_clip_y-y2)*(x1-x2)/(y1-y2);
// test if intersection is valid, of so then done, else compute next
if (xc2 < min_clip_x || xc2 > max_clip_x)
{
xc2 = min_clip_x;
yc2 = y2 + 0.5+(min_clip_x-x2)*(y1-y2)/(x1-x2);
} // end if
} break;
case CLIP_CODE_SW:
{
// south hline intersection
yc2 = max_clip_y;
xc2 = x2 + 0.5+(max_clip_y-y2)*(x1-x2)/(y1-y2);
// test if intersection is valid, of so then done, else compute next
if (xc2 < min_clip_x || xc2 > max_clip_x)
{
xc2 = min_clip_x;
yc2 = y2 + 0.5+(min_clip_x-x2)*(y1-y2)/(x1-x2);
} // end if
} break;
default:break;
} // end switch
// do bounds check
if ((xc1 < min_clip_x) || (xc1 > max_clip_x) ||
(yc1 < min_clip_y) || (yc1 > max_clip_y) ||
(xc2 < min_clip_x) || (xc2 > max_clip_x) ||
(yc2 < min_clip_y) || (yc2 > max_clip_y) )
{
return(0);
} // end if
// store vars back
x1 = xc1;
y1 = yc1;
x2 = xc2;
y2 = yc2;
return(1);
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