函数名: p_w_picpathsize
功能: 返回保存位图像所需的字节数
用法: unsigned far p_w_picpathsize(int left, int top, int right, int bottom);
程序例:
#include
#include
#include
#include
#define ARROW_SIZE 10
void draw_arrow(int x, int y);
int main(void)
{
/* request autodetection */
int gdriver = DETECT, gmode, errorcode;
void *arrow;
int x, y, maxx;
unsigned int size;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
{
printf("Graphics error: %s\n", grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
exit(1); /* terminate with an error code */
}
maxx = getmaxx();
x = 0;
y = getmaxy() / 2;
/* draw the p_w_picpath to be grabbed */
draw_arrow(x, y);
/* calculate the size of the p_w_picpath */
size = p_w_picpathsize(x, y-ARROW_SIZE, x+(4*ARROW_SIZE), y+ARROW_SIZE);
/* allocate memory to hold the p_w_picpath */
arrow = malloc(size);
/* grab the p_w_picpath */
getp_w_picpath(x, y-ARROW_SIZE, x+(4*ARROW_SIZE), y+ARROW_SIZE, arrow);
/* repeat until a key is pressed */
while (!kbhit())
{
/* erase old p_w_picpath */
putp_w_picpath(x, y-ARROW_SIZE, arrow, XOR_PUT);
x += ARROW_SIZE;
if (x >= maxx)
x = 0;
/* plot new p_w_picpath */
putp_w_picpath(x, y-ARROW_SIZE, arrow, XOR_PUT);
}
/* clean up */
free(arrow);
closegraph();
return 0;
}
void draw_arrow(int x, int y)
{
/* draw an arrow on the screen */
moveto(x, y);
linerel(4*ARROW_SIZE, 0);
linerel(-2*ARROW_SIZE, -1*ARROW_SIZE);
linerel(0, 2*ARROW_SIZE);
linerel(2*ARROW_SIZE, -1*ARROW_SIZE);
}
