rpi4-osdev/part12-wgt/wgt/wwarp.c

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#include "../include/wgt.h"
void wsline (short x, short y, short x2, short y2, short *y_array)
{
short t, distance;
short wx, wy, dx, dy, bdx, bdy, incx, incy;
dx = x2 - x;
dy = y2 - y;
t = 0; wx = 0; wy = 0;
if (dy < 0) incy = - 1;
else incy = 1;
if (dx < 0) incx = - 1;
else incx = 1;
bdx = abs (dx);
bdy = abs (dy);
if (bdx > bdy) distance = bdx;
else distance = bdy;
y_array += x;
if (distance == bdx)
{
while (t <= distance)
{
if ((x >= tx) && (y >= ty) && (y <= by) && (x <= bx))
*y_array = y;
/* instead of plotting pixels, just store the y value in an array */
wy += bdy;
x += incx;
y_array++;
t ++;
if (wy >= distance)
{
wy -= distance;
y += incy;
}
}
}
else
{
while (t <= distance)
{
if ((x >= tx) && (y >= ty) && (y <= by) && (x <= bx))
*y_array = y;
wx += bdx;
if (wx >= distance)
{
wx -= distance;
x += incx;
y_array++;
}
y += incy;
t ++;
}
}
}
void wwarp (short sx, short ex, short *tpy, short *bty, block ptr, short mode)
{
long column;
int wid;
short finalwidth;
short origwidth;
long xstepper;
origwidth = wgetblockwidth (ptr);
/* Get the original width of the block */
finalwidth = abs (ex - sx) + 1;
/* Find the new width */
xstepper = ((long)(origwidth) << 16) / ((long)(finalwidth));
/* Calculate the amount to add to the source bitmap for every pixel across.
This is done using a fixed point number by multiplying it by 65536 (<<16)
and using 0-65535 as a fractional amount. */
column = 0;
for (wid = sx; wid <= ex; wid++)
{
wresize_column (wid, tpy[wid], bty[wid], ptr, column >> 16, mode);
column += xstepper;
}
}