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jedi-academy/codemp/qcommon/cm_draw.cpp
James Monroe 684d1bcb3b Jedi Academy Release
2013-04-04 17:35:38 -05:00

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///////////////////////////////////////////////////////////////////////////////
// CDraw32 Class Implementation
//
// Basic drawing routines for 32-bit buffer
///////////////////////////////////////////////////////////////////////////////
//Anything above this #include will be ignored by the compiler
#include "../qcommon/exe_headers.h"
#include "cm_local.h"
#include "cm_draw.h"
///////////// statics for CDraw32 //////////////////////////////////
// Used by all drawing routines as the "current" drawing context
CPixel32* CDraw32::buffer = NULL; // pointer to 32-bit deep pixel buffer
long CDraw32::buf_width=0; // width of buffer in pixels
long CDraw32::buf_height=0; // height of buffer in pixels
long CDraw32::stride = 0; // stride in pixels
long CDraw32::clip_min_x=0; // clip bounds
long CDraw32::clip_min_y=0; // clip bounds
long CDraw32::clip_max_x=0; // clip bounds
long CDraw32::clip_max_y=0; // clip bounds
long* CDraw32::row_off = NULL; // Table for quick Y calculations
CDraw32::CDraw32()
//USE: constructor
{
}
CDraw32::~CDraw32()
//USE: Destructor
{
}
int imgKernel[5][5] =
{
{-1,-1,-1,-1, 0},
{-1,-1,-1, 0, 1},
{-1,-1, 0, 1, 1},
{-1, 0, 1, 1, 1},
{ 0, 1, 1, 1, 1}
};
const int KWIDTH = 2;
void CDraw32::Emboss(long dstX, long dstY, long width, long height,
CPixel32* clrImage, long clrX, long clrY, long clrStride)
{
CPixel32 *dst;
CPixel32 *clr;
int x,y,i,j;
int dstNextLine;
int clrNextLine;
assert(buffer != NULL);
BlitClip(dstX, dstY, width, height, clrX, clrY);
if (width < 1 || height < 1)
return;
dst = &buffer[PIXPOS(dstX,dstY,stride)];
clr = &clrImage[PIXPOS(clrX,clrY,clrStride)];
dstNextLine = (stride - width);
clrNextLine = (clrStride - width);
for (y = 0; y < height; y++)
{
for (x = 0; x < width; x++)
{
int accum = 0;
for (j = -KWIDTH; j<=KWIDTH; j++)
for (i = -KWIDTH; i<=KWIDTH; i++)
{
int xk = CLAMP(x + i, clrX, clrX+width-1);
int yk = CLAMP(y + j, clrY, clrY+height-1);
accum += clrImage[PIXPOS(xk,yk,clrStride)].a * imgKernel[j+KWIDTH][i+KWIDTH];
}
*dst = LIGHT_PIX(*clr, accum);
dst->a = 255;
++dst;
++clr;
}
dst += dstNextLine;
clr += clrNextLine;
}
}
bool CDraw32::SetBufferSize(long width,long height,long stride_len)
//USE: setup for a particular size drawing buffer
// (do not re-setup if buffer size has not changed)
//IN: width,height - size of buffer
// stride_len - distance to next line
//OUT: true if everything goes OK, otherwise false
{
long i;
assert(width!=0);
assert(height!=0);
assert(stride_len!=0);
if (buf_width != width || buf_height != height ||
stride_len != stride)
{ // need to re-create row_off table
buf_width = width;
buf_height = height;
stride = stride_len;
if (row_off)
delete [] row_off;
// row offsets used for quick pixel address calcs
row_off = new long[height];
assert(row_off != NULL);
if (row_off == NULL)
return false;
// table for quick pixel lookups
for (i=0; i<height; i++)
row_off[i] = i * stride;
}
// set default clip bounds
SetClip(0, 0, width-1, height-1);
return true;
}
void CDraw32::ClearLines(CPixel32 color,long start,long end)
//USE: clear screen buffer to color provided for lines
//IN: color - 32-bit color value
// start through end - line numbers
//OUT: none
{
CPixel32 *dest;
int line,i,next_line;
assert(buffer!=NULL);
assert(start>=0);
assert(end<buf_height);
dest = &buffer[row_off[start]];
next_line = stride - buf_width;
line = end - start + 1;
while (line-- != 0)
{ // very simple-minded fill loop
i = buf_width;
while (i--)
*dest++ = color;
dest += next_line;
}
}
void CDraw32::SetAlphaLines(byte alpha,long start,long end)
//USE: set the alpha value only
//IN: alpha - 8-bit alpha value
// start through end - line numbers
//OUT: none
{
CPixel32 *dest;
int line,i,next_line;
assert(buffer!=NULL);
assert(start>=0);
assert(end<buf_height);
dest = &buffer[row_off[start]];
next_line = stride - buf_width;
line = end - start + 1;
while (line-- != 0)
{ // very simple-minded fill loop
i = buf_width;
while (i--)
{
dest->a = alpha;
++dest;
}
dest += next_line;
}
}
#define LEFT 1 // code bits
#define RIGHT 2
#define TOP 4
#define BOTTOM 8
static long code(long x,long y)
//USE: determines where a point is in relation to a bounding box
//IN: x,y - coordinate pair
//OUT: clipping code compaired to global clip context
{
long c;
c = 0;
if (x < CDraw32::clip_min_x) c |= LEFT;
if (x > CDraw32::clip_max_x) c |= RIGHT;
if (y < CDraw32::clip_min_y) c |= BOTTOM;
if (y > CDraw32::clip_max_y) c |= TOP;
return c;
}
bool CDraw32::ClipLine(long& x1, long& y1, long& x2, long& y2)
//USE: clip a line from (x1,y1) to (x2,y2) to clip bounds
//IN: (x1,y1)-(x2,y2) line
//OUT: return true if something left to draw, otherwise false
{
long c1,c2,c,x,y,f;
x = x1;
y = y1;
c1 = code(x1,y1); // find where first pt. is
c2 = code(x2,y2); // find where second pt. is
if ((c1 & c2) == 0)
{ // the line may be visible
while (c1 | c2)
{ // where there is 2D clipping to be done
if (c1 & c2)
{
return false; // if both on same side, quit
}
c = c1;
if (c==0)
{
c = c2; // pick a point
}
if (c & TOP)
{
f = ((clip_max_y-y1) << 15)/(y2-y1);
x = x1 + (((x2-x1)*f + 16384) >> 15);
y = clip_max_y;
}
else if (c & BOTTOM)
{
f = ((clip_min_y-y1) << 15)/(y2-y1);
x = x1 + (((x2-x1)*f + 16384) >> 15);
y = clip_min_y;
}
else if (c & LEFT)
{
f = ((clip_min_x-x1) << 15)/(x2-x1);
y = y1 + (((y2-y1)*f + 16384) >> 15);
x = clip_min_x;
}
else if (c & RIGHT)
{
f = ((clip_max_x-x1) << 15)/(x2-x1);
y = y1 + (((y2-y1)*f + 16384) >> 15);
x = clip_max_x;
}
if (c==c1)
{
x1=x; y1=y; c1=code(x1,y1);
}
else
{
x2=x; y2=y; c2=code(x2,y2);
}
} // while still needs clipping
}
else
{ // line not visible
return false;
}
return true;
}
void CDraw32::DrawLineNC(long x1, long y1, long x2, long y2, CPixel32 color)
//USE: draw a line from (x1,y1) to (x2,y2) in color (no clip)
//IN: (x1,y1) - starting coordinate
// (x2,y2) - ending coordinate
// color - 32-bit color value
//OUT: none
{
long d, ax, ay, sx, sy, dx, dy;
CPixel32* dest;
assert(buffer != NULL);
dx = x2-x1;
ax = ABS(dx) << 1;
sx = SIGN(dx);
dy = y2-y1;
ay = ABS(dy) << 1;
sy = SIGN(dy);
if (255 == color.a)
{
if (dy == 0)
{ // horz line
if (dx >= 0)
{
dest = &buffer[row_off[y1] + x1];
int i = dx+1;
while (i--)
*dest++ = color;
}
else
{
dest = &buffer[row_off[y1] + x1 + dx];
int i = -dx+1;
while (i--)
*dest++ = color;
}
return;
}
if (dx == 0)
{ // vert line
if (dy >= 0)
{
dest = &buffer[row_off[y1] + x1];
dy++;
}
else
{
dest = &buffer[row_off[y2] + x1];
dy = -dy + 1;
}
while (dy-- != 0)
{
*dest = color;
dest += stride;
}
return;
}
}
// bressenham's algorithm
if (ax > ay)
{
d = ay - (ax >> 1);
while(x1 != x2)
{
PutPixAlphaNC(x1,y1,color);
if (d >= 0)
{
y1 += sy;
d -= ax;
}
x1 += sx;
d += ay;
}
}
else
{
d = ax - (ay >> 1);
while(y1 != y2)
{
PutPixAlphaNC(x1,y1,color);
if (d >= 0)
{
x1 += sx;
d -= ay;
}
y1 += sy;
d += ax;
}
}
PutPixAlphaNC(x1,y1,color);
}
void CDraw32::DrawLineAveNC(long x1, long y1, long x2, long y2, CPixel32 color)
//USE: draw a translucent line from (x1,y1) to (x2,y2) in color (no clip)
//IN: (x1,y1) - starting coordinate
// (x2,y2) - ending coordinate
// color - 32-bit color value
//OUT: none
{
long d, ax, ay, sx, sy, dx, dy;
CPixel32* dest;
assert(buffer != NULL);
dx = x2-x1;
ax = ABS(dx) << 1;
sx = SIGN(dx);
dy = y2-y1;
ay = ABS(dy) << 1;
sy = SIGN(dy);
if (dy == 0)
{ // horz line
if (dx >= 0)
{
dest = &buffer[row_off[y1] + x1];
int i = dx+1;
while (i--)
*dest++ = AVE_PIX(*dest, color);
}
else
{
dest = &buffer[row_off[y1] + x1 + dx];
int i = -dx+1;
while (i--)
*dest++ = AVE_PIX(*dest, color);
}
return;
}
if (dx == 0)
{ // vert line
if (dy >= 0)
{
dest = &buffer[row_off[y1] + x1];
dy++;
}
else
{
dest = &buffer[row_off[y2] + x1];
dy = -dy + 1;
}
while (dy-- != 0)
{
*dest = AVE_PIX(*dest, color);
dest += stride;
}
return;
}
// bressenham's algorithm
if (ax > ay)
{
d = ay - (ax >> 1);
while(x1 != x2)
{
PutPixAveNC(x1,y1,color);
if (d >= 0)
{
y1 += sy;
d -= ax;
}
x1 += sx;
d += ay;
}
}
else
{
d = ax - (ay >> 1);
while(y1 != y2)
{
PutPixAveNC(x1,y1,color);
if (d >= 0)
{
x1 += sx;
d -= ay;
}
y1 += sy;
d += ax;
}
}
PutPixAveNC(x1,y1,color);
}
void CDraw32::DrawLineAANC(long x0, long y0, long x1, long y1, CPixel32 color)
// Wu antialiased line drawer.
//USE: Function to draw an antialiased line from (x0,y0) to (x1,y1), using an
// antialiasing approach published by Xiaolin Wu in the July 1991 issue of
// Computer Graphics (SIGGRAPH proceedings).
//
//IN: (x0,y0),(x1,y1) = line to draw
// color = 32-bit color
//OUT: none
{
assert(buffer != NULL);
// Make sure the line runs top to bottom
if (y0 > y1)
{
SWAP(y0,y1);
SWAP(x0,x1);
}
long DeltaX = x1 - x0;
long DeltaY = y1 - y0;
long XDir;
// Draw the initial pixel, which is always exactly intersected by
// the line and so needs no Alpha
PutPixAlphaNC(x0, y0, color);
if (DeltaX >= 0)
{
XDir = 1;
}
else
{
XDir = -1;
DeltaX = -DeltaX; // make DeltaX positive
}
// Special-case horizontal, vertical, and diagonal lines, which
// require no Alpha because they go right through the center of
// every pixel
if (DeltaY == 0)
{ // Horizontal line
while (DeltaX-- != 0)
{
x0 += XDir;
PutPixAlphaNC(x0, y0, color);
}
return;
}
if (DeltaX == 0)
{ // Vertical line
do
{
y0++;
PutPixAlphaNC(x0, y0, color);
}
while (--DeltaY != 0);
return;
}
if (DeltaX == DeltaY)
{ // Diagonal line
do
{
x0 += XDir;
y0++;
PutPixAlphaNC(x0, y0, color);
}
while (--DeltaY != 0);
return;
}
// Line is not horizontal, diagonal, or vertical
unsigned short ErrorAcc = 0; // initialize the line error accumulator to 0
// # of bits by which to shift ErrorAcc to get intensity level
const unsigned long IntensityShift = 16 - 8;
// Is this an X-major or Y-major line?
if (DeltaY > DeltaX)
{
// Y-major line; calculate 16-bit fixed-point fractional part of a
// pixel that X advances each time Y advances 1 pixel, truncating the
// result so that we won't overrun the endpoint along the X axis
unsigned short ErrorAdj = unsigned short
(((unsigned long) DeltaX << 16) / (unsigned long) DeltaY);
// Draw all pixels other than the first and last
while (--DeltaY)
{
unsigned short ErrorAccTemp = ErrorAcc; // remember currrent accumulated error
ErrorAcc += ErrorAdj; // calculate error for next pixel
if (ErrorAcc <= ErrorAccTemp)
{ // The error accumulator turned over, so advance the X coord
x0 += XDir;
}
y0++; // Y-major, so always advance Y
// The IntensityBits most significant bits of ErrorAcc give us the
// intensity Alpha for this pixel, and the complement of the
// Alpha for the paired pixel
unsigned long Alpha = ErrorAcc >> IntensityShift;
unsigned long InvAlpha = 256-Alpha;
PutPixAlphaNC(x0, y0,
ALPHA_PIX(GetPix(x0, y0), color, Alpha, InvAlpha));
PutPixAlphaNC(x0+XDir, y0,
ALPHA_PIX(GetPix(x0+XDir, y0), color, InvAlpha, Alpha));
}
// Draw the final pixel, which is always exactly intersected by the line
// and so needs no Alpha
PutPixAlphaNC(x1, y1, color);
return;
}
// It's an X-major line; calculate 16-bit fixed-point fractional part of a
// pixel that Y advances each time X advances 1 pixel, truncating the
// result to avoid overrunning the endpoint along the X axis
unsigned short ErrorAdj = unsigned short
(((unsigned long) DeltaY << 16) / (unsigned long) DeltaX);
// Draw all pixels other than the first and last
while (--DeltaX)
{
unsigned short ErrorAccTemp = ErrorAcc; // remember currrent accumulated error
ErrorAcc += ErrorAdj; // calculate error for next pixel
if (ErrorAcc <= ErrorAccTemp)
{ // The error accumulator turned over, so advance the Y coord
y0++;
}
x0 += XDir; // X-major, so always advance X
// The IntensityBits most significant bits of ErrorAcc give us the
// intensity Alpha for this pixel, and the complement of the
// Alpha for the paired pixel
unsigned long Alpha = ErrorAcc >> IntensityShift;
unsigned long InvAlpha = 256-Alpha;
PutPixAlphaNC(x0, y0,
ALPHA_PIX(GetPix(x0, y0), color, Alpha, InvAlpha));
PutPixAlphaNC(x0, y0+1,
ALPHA_PIX(GetPix(x0, y0+1), color, InvAlpha, Alpha));
}
// Draw the final pixel, which is always exactly intersected by the line
// and so needs no Alpha
PutPixAlphaNC(x1, y1, color);
}
void CDraw32::DrawRectNC(long ulx, long uly, long width, long height, CPixel32 color)
//USE: draw rectangle in solid color, no clipping
//IN: (ulx,uly) - coordinates of upper-left corner of rect
// width, height - dimensions of rectangle
// color - color value
//OUT: none
{
assert(buffer != NULL);
assert(ulx>=0);
assert(uly>=0);
assert(ulx+width<buf_width);
assert(uly+height<buf_height);
if (height < 1 || width < 1)
return;
while (height-- != 0)
{
DrawLineNC(ulx, uly, ulx+width-1, uly, color);
uly++;
}
}
void CDraw32::DrawRect(long ulx, long uly, long width, long height, CPixel32 color)
//USE: draw rectangle in solid color
//IN: (ulx,uly) - coordinates of upper-left corner of rect
// width, height - dimensions of rectangle
// color - color value
//OUT: none
{
assert(buffer != NULL);
if (height < 1 || width < 1)
return;
while (height-- != 0)
{
DrawLine(ulx, uly, ulx+width-1, uly, color);
uly++;
}
}
void CDraw32::DrawRectAve(long ulx, long uly, long width, long height, CPixel32 color)
//USE: draw rectangle in solid color, translucent
//IN: (ulx,uly) - coordinates of upper-left corner of rect
// width, height - dimensions of rectangle
// color - color value
//OUT: none
{
assert(buffer != NULL);
if (height < 1 || width < 1)
return;
while (height-- != 0)
{
DrawLineAve(ulx, uly, ulx+width-1, uly, color);
uly++;
}
}
void CDraw32::DrawBoxNC(long ulx, long uly, long width, long height, CPixel32 color)
//USE: Draw an empty box, no clipping
//IN: (ulx,uly) - coordinates of upper-left corner of box
// width, height - dimensions of box
// color - color value
//OUT: none
{
assert(buffer != NULL);
if (height < 1 || width < 1)
return;
DrawLineNC(ulx, uly, ulx+width-1, uly, color);
DrawLineNC(ulx, uly+height-1, ulx+width-1, uly+height-1, color);
DrawLineNC(ulx, uly, ulx, uly+height-1, color);
DrawLineNC(ulx+width-1, uly, ulx+width-1, uly+height-1, color);
}
void CDraw32::DrawBox(long ulx, long uly, long width, long height, CPixel32 color)
//USE: Draw an empty box
//IN: (ulx,uly) - coordinates of upper-left corner of rect
// width, height - dimensions of rectangle
// color - color value
//OUT: none
{
assert(buffer != NULL);
if (height < 1 || width < 1)
return;
DrawLine(ulx, uly, ulx+width-1, uly, color);
DrawLine(ulx, uly+height-1, ulx+width-1, uly+height-1, color);
DrawLine(ulx, uly, ulx, uly+height-1, color);
DrawLine(ulx+width-1, uly, ulx+width-1, uly+height-1, color);
}
void CDraw32::DrawBoxAve(long ulx, long uly, long width, long height, CPixel32 color)
//USE: Draw an empty box, translucent
//IN: (ulx,uly) - coordinates of upper-left corner of rect
// width, height - dimensions of rectangle
// color - color value
//OUT: none
{
assert(buffer!=NULL);
if (height < 1 || width < 1)
return;
DrawLineAve(ulx, uly, ulx+width-1, uly, color);
DrawLineAve(ulx, uly+height-1, ulx+width-1, uly+height-1, color);
DrawLineAve(ulx, uly, ulx, uly+height-1, color);
DrawLineAve(ulx+width-1, uly, ulx+width-1, uly+height-1, color);
}
void CDraw32::DrawCircle(long xc, long yc, long r, CPixel32 edge, CPixel32 fill)
//USE: Draw a simple circle in current color with Bresenham's
// circle algorithm.
// See PROCEDURAL ELEMENTS FOR COMPUTER GRAPHICS
// David F. Rogers Pg. 48.
//
//IN: xc,yc - center
// r - radius
// edge - edge color
// fill - fill color
//
//OUT: NONE (a circle drawn in the off-screen buffer)
{
long x,y;
long limit,di,delta;
long last_x,last_y;
assert(buffer != NULL);
if (r < 1)
return;
// draw fill
if (fill.a != 0)
{
x = 0; last_x = x;
y = r; last_y = y;
di = 2*(1-r);
limit = 0;
do
{
if (y >= limit)
{
if (di < 0)
{
delta = 2*di + 2*y - 1;
if (delta <= 0)
{ // move horizontal
last_x = x;
x++;
di += (2*x + 1);
}
else
{ // move diagonal
last_x = x;
x++;
y--;
di += (2*x - 2*y + 2);
}
}
else
{
if (di > 0)
{
delta = 2*di - 2*x -1;
if (delta <= 0)
{ // move diagonal
last_x = x;
x++;
y--;
di += (2*x - 2*y + 2);
}
else
{ // move vertical
y--;
di += (1 - 2*y);
}
}
else /* di = 0 */
{ // move diagonal
last_x = x;
x++;
y--;
di += (2*x - 2*y + 2);
}
}
}
if (y != last_y)
{ // circle fill
DrawLine(xc-last_x,yc+last_y,xc+last_x,yc+last_y,fill);
if (last_y > limit)
{
DrawLine(xc-last_x,yc-last_y,xc+last_x,yc-last_y,fill);
}
last_y = y;
}
} while (y >= limit);
}
// draw edge
if (edge.a != 0)
{
x = 0;
y = r;
limit = 0;
di = 2*(1-r);
do
{
// circle edge
PutPix(xc+x, yc+y, edge);
PutPix(xc-x, yc+y, edge);
if (y > limit)
{
PutPix(xc+x, yc-y, edge);
PutPix(xc-x, yc-y, edge);
}
if (y >= limit)
{
if (di < 0)
{
delta = 2*di + 2*y - 1;
if (delta <= 0)
{ // move horizontal
x++;
di += (2*x + 1);
}
else
{ // move diagonal
x++;
y--;
di += (2*x - 2*y + 2);
}
}
else
{
if (di > 0)
{
delta = 2*di - 2*x -1;
if (delta <= 0)
{ // move diagonal
x++;
y--;
di += (2*x - 2*y + 2);
}
else
{ // move vertical
y--;
di += (1 - 2*y);
}
}
else /* di = 0 */
{ // move diagonal
x++;
y--;
di += (2*x - 2*y + 2);
}
}
}
} while (y >= limit);
}
} // DrawCircle
void CDraw32::DrawCircleAve(long xc, long yc, long r, CPixel32 edge, CPixel32 fill)
//USE: Draw a simple circle in current color with Bresenham's
// circle algorithm.
// a circle with fill and edge colors averaged with dest (-1 = no color)
// See PROCEDURAL ELEMENTS FOR COMPUTER GRAPHICS
// David F. Rogers Pg. 48.
//
//IN: xc,yc - center
// r - radius
// edge - edge color
// fill - fill color
//
//OUT: none (a circle on in the off-screen buffer)
{
long x,y;
long limit,di,delta;
long last_x,last_y;
long f;
assert(buffer != NULL);
if (r < 1)
return;
// draw fill
if (fill.a != 0)
{
x = 0; last_x = x;
y = r; last_y = y;
di = 2*(1-r);
limit = 0;
do
{
if (y >= limit)
{
if (di < 0)
{
delta = 2*di + 2*y - 1;
if (delta <= 0)
{ // move horizontal
last_x = x;
x++;
di += (2*x + 1);
}
else
{ // move diagonal
last_x = x;
x++;
y--;
di += (2*x - 2*y + 2);
}
}
else
{
if (di > 0)
{
delta = 2*di - 2*x -1;
if (delta <= 0)
{ // move diagonal
last_x = x;
x++;
y--;
di += (2*x - 2*y + 2);
}
else
{ // move vertical
y--;
di += (1 - 2*y);
}
}
else /* di = 0 */
{ // move diagonal
last_x = x;
x++;
y--;
di += (2*x - 2*y + 2);
}
}
}
if (y != last_y)
{ // circle fill
for (f=xc-last_x; f<=xc+last_x; f++)
PutPixAve(f, yc+last_y, fill);
if (last_y > limit)
{
for (f=xc-last_x; f<=xc+last_x; f++)
PutPixAve(f, yc-last_y, fill);
}
last_y = y;
}
} while (y >= limit);
}
// draw edge
if (edge.a != 0)
{
x = 0;
y = r;
limit = 0;
di = 2*(1-r);
do
{
// circle edge
PutPixAve(xc+x, yc+y, edge);
PutPixAve(xc-x, yc+y, edge);
if (y > limit)
{
PutPixAve(xc+x, yc-y, edge);
PutPixAve(xc-x, yc-y, edge);
}
if (y >= limit)
{
if (di < 0)
{
delta = 2*di + 2*y - 1;
if (delta <= 0)
{ // move horizontal
x++;
di += (2*x + 1);
}
else
{ // move diagonal
x++;
y--;
di += (2*x - 2*y + 2);
}
}
else
{
if (di > 0)
{
delta = 2*di - 2*x -1;
if (delta <= 0)
{ // move diagonal
x++;
y--;
di += (2*x - 2*y + 2);
}
else
{ // move vertical
y--;
di += (1 - 2*y);
}
}
else /* di = 0 */
{ // move diagonal
x++;
y--;
di += (2*x - 2*y + 2);
}
}
}
} while (y >= limit);
}
} // DrawCircleAve
////////////////////////////////////////////////////////////////////////////
//Concave Polygon Scan Conversion
////////////////////////////////////////////////////////////////////////////
// concave: scan convert nvert-sided concave non-simple polygon
// with vertices at (point[i].x, point[i].y) for i in
// [0..nvert-1] within the window win by
// calling spanproc for each visible span of pixels.
//
// Polygon can be clockwise or counterclockwise.
//
// Algorithm does uniform point sampling at pixel centers.
// Inside-outside test done by even-odd rule: a point is
// considered inside if an emanating ray intersects the polygon
// an odd number of times.
//
// spanproc should fill in pixels from xl to xr inclusive on scanline y,
//
// e.g:
// spanproc(short y, short xl, short xr)
// {
// short x;
// for (x=xl; x<=xr; x++)
// pixel_write(x, y, pixelvalue);
// }
typedef struct
{ // a polygon edge
// these are fixed point long ints for some accuracy & speed
long x; // x coordinate of edge's intersection with current scanline
long dx; // change in x with respect to y
long i; // edge number: edge i goes from pt[i] to
// pt[i+1]
} POLYEDGE;
#define INT_SHIFT 13
// global for speed
static long n; // number of vertices
static POINT *pt; // vertices
static long nact; // number of active edges
static POLYEDGE active[256]; // active edge list:edges crossing scanline y
static long ind[256]; // list of vertex indices, sorted by
// pt[ind[j]].y
static void del_edge(long i)
// remove edge i from active list
{
int j;
for (j = 0; j < nact && active[j].i != i; j++)
;
// edge not in active list; happens at cliprect->top
if (j >= nact)
{
return;
}
nact--;
memcpy(&active[j], &active[j + 1], (nact - j) * sizeof(active[0]));
}
static void ins_edge(long i, long y)
// append edge i to end of active list
{
int j;
long dx;
POINT *p;
POINT *q;
j = i < n - 1 ? i + 1 : 0;
if (pt[i].y < pt[j].y)
{
p = &pt[i];
q = &pt[j];
}
else
{
p = &pt[j];
q = &pt[i];
}
// initialize x position at intersection of edge with scanline y
if ((q->y - p->y) != 0)
{
dx = (((long)q->x - (long)p->x) * (long)(1<<INT_SHIFT));
dx /= (((long)q->y - (long)p->y));
}
else
{
// horizontal line
dx = 0;
}
active[nact].dx = dx;
active[nact].x = (dx * (long)(y - p->y)) + ((long)p->x << INT_SHIFT);
active[nact].i = i;
nact++;
}
// comparison routines for shellsort
int compare_ind(long *u, long *v)
{
return (pt[*u].y <= pt[*v].y ? -1 : 1);
}
int compare_active(POLYEDGE *u, POLYEDGE *v)
{
return (u->x <= v->x ? -1 : 1);
}
void shell_sort(void *vec, long n, long siz,
int (*compare)(void*,void*))
// USE: shell sort aka heap sort. Best sort algorithm for almost sorted list.
{
byte *a;
byte v[128]; // temp object
long i,j,h;
a = (byte *)vec;
// choose size of "heap"
for (h = 1; h <= n/9; h = 3*h+1)
;
// divide and conq.
for ( ; h > 0; h /= 3)
{
for (i = h; i < n; i++)
{
// v = a[i];
memcpy(v,(a+i*siz),siz);
j = i;
// j >= h && a[j-h] > v
while ((j >= h) && compare((void*)(a+(j-h)*siz),(void*)v) > 0)
{
// a[j] = a[j-h]
memcpy((a+j*siz),(a+(j-h)*siz),siz);
j -= h;
}
// a[j] = v;
memcpy((a+j*siz),v,siz);
}
}
}
void CDraw32::DrawPolygon(long nvert, POINT *point, CPixel32 edge, CPixel32 fill)
//USE: Scan convert a polygon
//IN: nvert: Number of vertices
// point: Vertices of polygon
// edge: edge color
// fill: fill color
//OUT: none
{
long k,
y0,
y1,
y,
i,
j,
xl,
xr;
assert(buffer != NULL);
n = nvert;
if (n <= 0)
{ // nothing to do
return;
}
pt = point;
if (fill.a != 0)
{ // draw fill
// create y-sorted array of indices ind[k] into vertex list
for (k = 0; k < n; k++)
{
ind[k] = k;
}
// sort ind by pt[ind[k]].y
shell_sort(ind, n, sizeof(long), (int (*)(void*,void*)) compare_ind);
nact = 0; // start with empty active list
k = 0; // ind[k] is next vertex to process
// ymin of polygon
y0 = MAX(clip_min_y-1, pt[ind[0]].y);
// ymax of polygon
y1 = MIN(clip_max_y+1, pt[ind[n-1]].y);
// step through scanlines
for (y = y0; y < y1; y++)
{
// Check vertices between previous scanline
// and current one, if any
for (; (k < n) && (pt[ind[k]].y <= y); k++)
{
i = ind[k];
// insert or delete edges before and after vertex i
// (i-1 to i, and i to i+1)
// from active list if they cross scanline y
j = i > 0 ? i - 1 : n - 1; // vertex previous to i
if (pt[j].y < y)
{
// old edge, remove from active list
del_edge(j);
}
else
{
if (pt[j].y > y)
{
// new edge, add to active list
ins_edge(j, y);
}
}
j = i < n - 1 ? i + 1 : 0; // vertex next after i
if (pt[j].y < y)
{
// old edge, remove from active list
del_edge(i);
}
else
{
if (pt[j].y > y)
{
// new edge, add to active list
ins_edge(i, y);
}
}
}
// sort active edge list by active[j].x
shell_sort(active, nact, sizeof(POLYEDGE), (int (*)(void*,void*))compare_active);
// draw horizontal segments for scanline y
for (j = 0; j < nact; j += 2)
{ // draw horizontal segments
// span 'tween j & j+1 is inside, span tween
// j+1 & j+2 is outside
// left end of span
// convert back from fixed point - round down
xl = (long) (active[j].x >> INT_SHIFT);
if (xl < clip_min_x-1)
{
xl = clip_min_x-1;
}
// right end of span
// convert back from fixed point - round down
xr = (long) (active[j + 1].x >> INT_SHIFT);
if (xr > clip_max_x)
{
xr = clip_max_x;
}
if (xl < xr)
{
// draw pixels in span
DrawLine(xl+1,y,xr,y,fill);
}
// increment edge coords
active[j].x += active[j].dx;
active[j + 1].x += active[j + 1].dx;
}
}
// sort active edge list by active[j].x
shell_sort(active, nact, sizeof(POLYEDGE), (int (*)(void*,void*))compare_active);
// draw horizontal segments for scanline y
for (j = 0; j < nact; j += 2)
{ // draw horizontal segments
// span 'tween j & j+1 is inside, span tween
// j+1 & j+2 is outside
// left end of span
// convert back from fixed point - round down
xl = (long) (active[j].x >> INT_SHIFT);
if (xl < clip_min_x-1)
{
xl = clip_min_x-1;
}
// right end of span
// convert back from fixed point - round up
xr = (long) (active[j + 1].x >> INT_SHIFT);
if (xr > clip_max_x)
{
xr = clip_max_x;
}
if (xl < xr)
{
// draw pixels in span
DrawLine(xl+1,y,xr,y,fill);
}
// increment edge coords
active[j].x += active[j].dx;
active[j + 1].x += active[j + 1].dx;
}
}
if (edge.a != 0)
{ // draw edges
for (k = 0; k < n-1; k++)
{
DrawLineAA(pt[k].x,pt[k].y,pt[k+1].x,pt[k+1].y,edge);
}
DrawLineAA(pt[n-1].x,pt[n-1].y,pt[0].x,pt[0].y,edge);
}
return;
}
void CDraw32::Blit(long dstX, long dstY, long width, long height,
CPixel32* srcImage, long srcX, long srcY, long srcStride)
//USE: simple blit
//IN: dstX, dstY - upper left corner of where image will land in buffer
// width, height - width and height of image
// srcImage - src image buffer
// srcX, srcY - upper left corner in src image
// srcStride - number of pixels per line in src image
//OUT: none
{
CPixel32 *dst;
CPixel32 *src;
int x,y;
assert(buffer != NULL);
BlitClip(dstX, dstY, width, height, srcX, srcY);
if (width < 1 || height < 1)
return;
dst = &buffer[PIXPOS(dstX,dstY,stride)];
src = &srcImage[PIXPOS(srcX,srcY,srcStride)];
for (y = 0; y < height; y++)
{
for (x = 0; x < width; x++)
{
// *dst++ = *src++;
byte alpha = src->a;
byte dst_alpha = dst->a;
*dst = ALPHA_PIX(*src, *dst, alpha, 256-alpha);
dst->a = dst_alpha;
++dst;
++src;
}
dst += (stride - width);
src += (srcStride - width);
}
}
void CDraw32::BlitClip(long& dstX, long& dstY,
long& width, long& height,
long& srcX, long& srcY)
//USE: simple blit clip
//IN: dstX, dstY - upper left corner of where image will land in buffer
// width, height - width and height of image
// srcX, srcY - upper left corner in src image
//OUT: none
{
// clip to our buffer size
if (dstX < clip_min_x)
{
int dif = (clip_min_x - dstX);
dstX += dif;
srcX += dif;
width -= dif;
}
if (dstY < clip_min_y)
{
int dif = (clip_min_y - dstY);
dstY += dif;
srcY += dif;
height -= dif;
}
if (dstX+width-1 > clip_max_x)
{
width -= (dstX+width-1 - clip_max_x);
}
if (dstY+height-1 > clip_max_y)
{
height -= (dstY+height-1 - clip_max_y);
}
}
void CDraw32::BlitColor(long dstX, long dstY, long width, long height,
CPixel32* srcImage, long srcX, long srcY, long srcStride, CPixel32 color)
//USE: blit using image alpha as mask
//IN: dstX, dstY - upper left corner of where image will land in buffer
// width, height - width and height of image
// srcImage - src image buffer
// srcX, srcY - upper left corner in src image
// srcStride - number of pixels per line in src image
// color - color to apply to srcImage
//OUT: none
{
CPixel32 *dst;
CPixel32 *src;
int x,y;
int dstNextLine;
int srcNextLine;
assert(buffer != NULL);
BlitClip(dstX, dstY, width, height, srcX, srcY);
if (width < 1 || height < 1)
return;
dst = &buffer[PIXPOS(dstX,dstY,stride)];
src = &srcImage[PIXPOS(srcX,srcY,srcStride)];
dstNextLine = (stride - width);
srcNextLine = (srcStride - width);
for (y = 0; y < height; y++)
{
for (x = 0; x < width; x++)
{
byte alpha = src->a;
*dst = ALPHA_PIX(color, *dst, alpha, 256-alpha);
++dst;
++src;
}
dst += dstNextLine;
src += srcNextLine;
}
}
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