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<META name=vsisbn content="1576101746">
<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
<META name=vsauthor content="Michael Abrash">
<META name=vspublisher content="The Coriolis Group">
<META name=vspubdate content="07/01/97">
<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: Who Was that Masked Image?</TITLE>
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<P><B>LISTING 46.1 L46-1.C</B></P>
<!-- CODE //-->
<PRE>
/* Sample simple dirty-rectangle animation program, partially optimized and
featuring internal animation, masked images (sprites), and nonoverlapping dirty
rectangle copying. Tested with Borland C&#43;&#43; in the small model. */
#include &ltstdlib.h&gt
#include &ltconio.h&gt
#include &ltalloc.h&gt
#include &ltmemory.h&gt
#include &ltdos.h&gt
/* Comment out to disable overlap elimination in the dirty rectangle list. */
#define CHECK-OVERLAP 1
#define SCREEN-WIDTH 320
#define SCREEN-HEIGHT 200
#define SCREEN-SEGMENT 0xA000
/* Describes a dirty rectangle */
typedef struct {
void *Next; /* pointer to next node in linked dirty rect list */
int Top;
int Left;
int Right;
int Bottom;
} DirtyRectangle;
/* Describes an animated object */
typedef struct {
int X; /* upper left corner in virtual bitmap */
int Y;
int XDirection; /* direction and distance of movement */
int YDirection;
int InternalAnimateCount; /* tracking internal animation state */
int InternalAnimateMax; /* maximum internal animation state */
} Entity;
/* storage used for dirty rectangles */
#define MAX-DIRTY-RECTANGLES 100
int NumDirtyRectangles;
DirtyRectangle DirtyRectangles[MAX-DIRTY-RECTANGLES];
/* head/tail of dirty rectangle list */
DirtyRectangle DirtyHead;
/* If set to 1, ignore dirty rectangle list and copy the whole screen. */
int DrawWholeScreen = 0;
/* pixels and masks for the two internally animated versions of the image
we&#146;ll animate */
#define IMAGE-WIDTH 13
#define IMAGE-HEIGHT 11
char ImagePixels0[] = {
0, 0, 0, 9, 9, 9, 9, 9, 0, 0, 0, 0, 0,
0, 0, 9, 9, 9, 9, 9, 9, 9, 0, 0, 0, 0,
0, 9, 9, 0, 0,14,14,14, 9, 9, 0, 0, 0,
9, 9, 0, 0, 0, 0,14,14,14, 9, 9, 0, 0,
9, 9, 0, 0, 0, 0,14,14,14, 9, 9, 0, 0,
9, 9,14, 0, 0,14,14,14,14, 9, 9, 0, 0,
9, 9,14,14,14,14,14,14,14, 9, 9, 0, 0,
9, 9,14,14,14,14,14,14,14, 9, 9, 0, 0,
0, 9, 9,14,14,14,14,14, 9, 9, 0, 0, 0,
0, 0, 9, 9, 9, 9, 9, 9, 9, 0, 0, 0, 0,
0, 0, 0, 9, 9, 9, 9, 9, 0, 0, 0, 0, 0,
};
char ImageMask0[] = {
0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0,
1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0,
1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0,
1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0,
0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
};
char ImagePixels1[] = {
0, 0, 0, 9, 9, 9, 9, 9, 0, 0, 0, 0, 9,
0, 0, 9, 9, 9, 9, 9, 9, 9, 0, 9, 9, 9,
0, 9, 9, 0, 0,14,14,14, 9, 9, 9, 9, 0,
9, 9, 0, 0, 0, 0,14,14,14, 0, 0, 0, 0,
9, 9, 0, 0, 0, 0,14,14, 0, 0, 0, 0, 0,
9, 9,14, 0, 0,14,14,14, 0, 0, 0, 0, 0,
9, 9,14,14,14,14,14,14, 0, 0, 0, 0, 0,
9, 9,14,14,14,14,14,14,14, 0, 0, 0, 0,
0, 9, 9,14,14,14,14,14, 9, 9, 9, 9, 0,
0, 0, 9, 9, 9, 9, 9, 9, 9, 0, 9, 9, 9,
0, 0, 0, 9, 9, 9, 9, 9, 0, 0, 0, 9, 9,
};
char ImageMask1[] = {
0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,
0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1,
0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0,
1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0,
1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0,
1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0,
0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1,
0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1,
};
/* Pointers to pixel and mask data for various internally animated
versions of our animated image. */
char * ImagePixelArray[] = {ImagePixels0, ImagePixels1};
char * ImageMaskArray[] = {ImageMask0, ImageMask1};
/* Animated entities */
#define NUM-ENTITIES 15
Entity Entities[NUM-ENTITIES];
/* pointer to system buffer into which we&#146;ll draw */
char far *SystemBufferPtr;
/* pointer to screen */
char far *ScreenPtr;
void EraseEntities(void);
void CopyDirtyRectanglesToScreen(void);
void DrawEntities(void);
void AddDirtyRect(Entity *, int, int);
void DrawMasked(char far *, char *, char *, int, int, int);
void FillRect(char far *, int, int, int, int);
void CopyRect(char far *, char far *, int, int, int, int);
void main()
{
int i, XTemp, YTemp;
unsigned int TempCount;
char far *TempPtr;
union REGS regs;
/* Allocate memory for the system buffer into which we&#146;ll draw */
if (!(SystemBufferPtr = farmalloc((unsigned int)SCREEN-WIDTH*
SCREEN-HEIGHT))) {
printf(&#148;Couldn&#146;t get memory\n&#148;);
exit(1);
}
/* Clear the system buffer */
TempPtr = SystemBufferPtr;
for (TempCount = ((unsigned)SCREEN-WIDTH*SCREEN-HEIGHT); TempCount--; ) {
*TempPtr&#43;&#43; = 0;
}
/* Point to the screen */
ScreenPtr = MK-FP(SCREEN-SEGMENT, 0);
/* Set up the entities we&#146;ll animate, at random locations */
randomize();
for (= 0; &lt NUM-ENTITIES; i&#43;&#43;) {
Entities[i].X = random(SCREEN-WIDTH - IMAGE-WIDTH);
Entities[i].Y = random(SCREEN-HEIGHT - IMAGE-HEIGHT);
Entities[i].XDirection = 1;
Entities[i].YDirection = -1;
Entities[i].InternalAnimateCount = &amp 1;
Entities[i].InternalAnimateMax = 2;
}
/* Set the dirty rectangle list to empty, and set up the head/tail node
as a sentinel */
NumDirtyRectangles = 0;
DirtyHead.Next = &ampDirtyHead;
DirtyHead.Top = 0x7FFF;
DirtyHead.Left= 0x7FFF;
DirtyHead.Bottom = 0x7FFF;
DirtyHead.Right = 0x7FFF;
/* Set 320x200 256-color graphics mode */
regs.x.ax = 0x0013;
int86(0x10, &ampregs, &ampregs);
/* Loop and draw until a key is pressed */
do {
/* Draw the entities to the system buffer at their current locations,
updating the dirty rectangle list */
DrawEntities();
/* Draw the dirty rectangles, or the whole system buffer if
appropriate */
CopyDirtyRectanglesToScreen();
/* Reset the dirty rectangle list to empty */
NumDirtyRectangles = 0;
DirtyHead.Next = &ampDirtyHead;
/* Erase the entities in the system buffer at their old locations,
updating the dirty rectangle list */
EraseEntities();
/* Move the entities, bouncing off the edges of the screen */
for (= 0; &lt NUM-ENTITIES; i&#43;&#43;) {
XTemp = Entities[i].X + Entities[i].XDirection;
YTemp = Entities[i].Y + Entities[i].YDirection;
if ((XTemp &lt 0) || ((XTemp + IMAGE-WIDTH) &gt SCREEN-WIDTH)) {
Entities[i].XDirection = -Entities[i].XDirection;
XTemp = Entities[i].X + Entities[i].XDirection;
}
if ((YTemp &lt 0) || ((YTemp + IMAGE-HEIGHT) &gt SCREEN-HEIGHT)) {
Entities[i].YDirection = -Entities[i].YDirection;
YTemp = Entities[i].Y + Entities[i].YDirection;
}
Entities[i].X = XTemp;
Entities[i].Y = YTemp;
}
} while (!kbhit());
getch(); /* clear the keypress */
/* Return back to text mode */
regs.x.ax = 0x0003;
int86(0x10, &ampregs, &ampregs);
}
/* Draw entities at their current locations, updating dirty rectangle list. */
void DrawEntities()
{
int i;
char far *RowPtrBuffer;
char *TempPtrImage;
char *TempPtrMask;
Entity *EntityPtr;
for (= 0, EntityPtr = Entities; &lt NUM-ENTITIES; i&#43;&#43;, EntityPtr&#43;&#43;) {
/* Remember the dirty rectangle info for this entity */
AddDirtyRect(EntityPtr, IMAGE-HEIGHT, IMAGE-WIDTH);
/* Point to the destination in the system buffer */
RowPtrBuffer = SystemBufferPtr + (EntityPtr-&gtY * SCREEN-WIDTH) +
EntityPtr-&gtX;
/* Advance the image animation pointer */
if (&#43;&#43;EntityPtr-&gtInternalAnimateCount &gt=
EntityPtr-&gtInternalAnimateMax) {
EntityPtr-&gtInternalAnimateCount = 0;
}
/* Point to the image and mask to draw */
TempPtrImage = ImagePixelArray[EntityPtr-&gtInternalAnimateCount];
TempPtrMask = ImageMaskArray[EntityPtr-&gtInternalAnimateCount];
DrawMasked(RowPtrBuffer, TempPtrImage, TempPtrMask, IMAGE-HEIGHT,
IMAGE-WIDTH, SCREEN-WIDTH);
}
}
/* Copy the dirty rectangles, or the whole system buffer if appropriate,
to the screen. */
void CopyDirtyRectanglesToScreen()
{
int i, RectWidth, RectHeight;
unsigned int Offset;
DirtyRectangle * DirtyPtr;
if (DrawWholeScreen) {
/* Just copy the whole buffer to the screen */
DrawWholeScreen = 0;
CopyRect(ScreenPtr, SystemBufferPtr, SCREEN-HEIGHT, SCREEN-WIDTH,
SCREEN-WIDTH, SCREEN-WIDTH);
} else {
/* Copy only the dirty rectangles, in the YX-sorted order in which
they&#146;re linked */
DirtyPtr = DirtyHead.Next;
for (= 0; &lt NumDirtyRectangles; i&#43;&#43;) {
/* Offset in both system buffer and screen of image */
Offset = (unsigned int) (DirtyPtr-&gtTop * SCREEN-WIDTH) +
DirtyPtr-&gtLeft;
/* Dimensions of dirty rectangle */
RectWidth = DirtyPtr-&gtRight - DirtyPtr-&gtLeft;
RectHeight = DirtyPtr-&gtBottom - DirtyPtr-&gtTop;
/* Copy a dirty rectangle */
CopyRect(ScreenPtr + Offset, SystemBufferPtr + Offset,
RectHeight, RectWidth, SCREEN-WIDTH, SCREEN-WIDTH);
/* Point to the next dirty rectangle */
DirtyPtr = DirtyPtr-&gtNext;
}
}
}
/* Erase the entities in the system buffer at their current locations,
updating the dirty rectangle list. */
void EraseEntities()
{
int i;
char far *RowPtr;
for (= 0; &lt NUM-ENTITIES; i&#43;&#43;) {
/* Remember the dirty rectangle info for this entity */
AddDirtyRect(&ampEntities[i], IMAGE-HEIGHT, IMAGE-WIDTH);
/* Point to the destination in the system buffer */
RowPtr = SystemBufferPtr + (Entities[i].Y * SCREEN-WIDTH) +
Entities[i].X;
/* Clear the rectangle */
FillRect(RowPtr, IMAGE-HEIGHT, IMAGE-WIDTH, SCREEN-WIDTH, 0);
}
}
/* Add a dirty rectangle to the list. The list is maintained in top-to-bottom,
left-to-right (YX sorted) order, with no pixel ever included twice, to minimize
the number of display memory accesses and to avoid screen artifacts resulting
from a large time interval between erasure and redraw for a given object or for
adjacent objects. The technique used is to check for overlap between the
rectangle and all rectangles already in the list. If no overlap is found, the
rectangle is added to the list. If overlap is found, the rectangle is broken
into nonoverlapping pieces, and the pieces are added to the list by recursive
calls to this function. */
void AddDirtyRect(Entity * pEntity, int ImageHeight, int ImageWidth)
{
DirtyRectangle * DirtyPtr;
DirtyRectangle * TempPtr;
Entity TempEntity;
int i;
if (NumDirtyRectangles &gt= MAX-DIRTY-RECTANGLES) {
/* Too many dirty rectangles; just redraw the whole screen */
DrawWholeScreen = 1;
return;
}
/* Remember this dirty rectangle. Break up if necessary to avoid
overlap with rectangles already in the list, then add whatever
rectangles are left, in YX sorted order */
#ifdef CHECK-OVERLAP
/* Check for overlap with existing rectangles */
TempPtr = DirtyHead.Next;
for (= 0; &lt NumDirtyRectangles; i&#43;&#43;, TempPtr = TempPtr-&gtNext) {
if ((TempPtr-&gtLeft &lt (pEntity-&gtX + ImageWidth)) &amp&amp
(TempPtr-&gtRight &gt pEntity-&gtX) &amp&amp
(TempPtr-&gtTop &lt (pEntity-&gtY + ImageHeight)) &amp&amp
(TempPtr-&gtBottom &gt pEntity-&gtY)) {
/* We&#146;ve found an overlapping rectangle. Calculate the
rectangles, if any, remaining after subtracting out the
overlapped areas, and add them to the dirty list */
/* Check for a nonoverlapped left portion */
if (TempPtr-&gtLeft &gt pEntity-&gtX) {
/* There&#146;s definitely a nonoverlapped portion at the left; add
it, but only to at most the top and bottom of the overlapping
rect; top and bottom strips are taken care of below */
TempEntity.X = pEntity-&gtX;
TempEntity.Y = max(pEntity-&gtY, TempPtr-&gtTop);
AddDirtyRect(&ampTempEntity,
min(pEntity-&gtY + ImageHeight, TempPtr-&gtBottom) -
TempEntity.Y,
TempPtr-&gtLeft - pEntity-&gtX);
}
/* Check for a nonoverlapped right portion */
if (TempPtr-&gtRight &lt (pEntity-&gtX + ImageWidth)) {
/* There&#146;s definitely a nonoverlapped portion at the right; add
it, but only to at most the top and bottom of the overlapping
rect; top and bottom strips are taken care of below */
TempEntity.X = TempPtr-&gtRight;
TempEntity.Y = max(pEntity-&gtY, TempPtr-&gtTop);
AddDirtyRect(&ampTempEntity,
min(pEntity-&gtY + ImageHeight, TempPtr-&gtBottom) -
TempEntity.Y,
(pEntity-&gtX + ImageWidth) - TempPtr-&gtRight);
}
/* Check for a nonoverlapped top portion */
if (TempPtr-&gtTop &gt pEntity-&gtY) {
/* There&#146;s a top portion that&#146;s not overlapped */
TempEntity.X = pEntity-&gtX;
TempEntity.Y = pEntity-&gtY;
AddDirtyRect(&ampTempEntity, TempPtr-&gtTop - pEntity-&gtY, ImageWidth);
}
/* Check for a nonoverlapped bottom portion */
if (TempPtr-&gtBottom &lt (pEntity-&gtY + ImageHeight)) {
/* There&#146;s a bottom portion that&#146;s not overlapped */
TempEntity.X = pEntity-&gtX;
TempEntity.Y = TempPtr-&gtBottom;
AddDirtyRect(&ampTempEntity,
(pEntity-&gtY + ImageHeight) - TempPtr-&gtBottom, ImageWidth);
}
/* We&#146;ve added all non-overlapped portions to the dirty list */
return;
}
}
#endif /* CHECK-OVERLAP */
/* There&#146;s no overlap with any existing rectangle, so we can just
add this rectangle as-is */
/* Find the YX-sorted insertion point. Searches will always terminate,
because the head/tail rectangle is set to the maximum values */
TempPtr = &ampDirtyHead;
while (((DirtyRectangle *)TempPtr-&gtNext)-&gtTop &lt pEntity-&gtY) {
TempPtr = TempPtr-&gtNext;
}
while ((((DirtyRectangle *)TempPtr-&gtNext)-&gtTop == pEntity-&gtY) &amp&amp
(((DirtyRectangle *)TempPtr-&gtNext)-&gtLeft &lt pEntity-&gtX)) {
TempPtr = TempPtr-&gtNext;
}
/* Set the rectangle and actually add it to the dirty list */
DirtyPtr = &ampDirtyRectangles[NumDirtyRectangles&#43;&#43;];
DirtyPtr-&gtLeft = pEntity-&gtX;
DirtyPtr-&gtTop = pEntity-&gtY;
DirtyPtr-&gtRight = pEntity-&gtX + ImageWidth;
DirtyPtr-&gtBottom = pEntity-&gtY + ImageHeight;
DirtyPtr-&gtNext = TempPtr-&gtNext;
TempPtr-&gtNext = DirtyPtr;
}
</PRE>
<!-- END CODE //-->
<P><B>LISTING 46.2 L46-2.ASM</B></P>
<!-- CODE //-->
<PRE>
; Assembly language helper routines for dirty rectangle animation. Tested with
; TASM.
; Fills a rectangle in the specified buffer.
; C-callable as:
; void FillRect(char far * BufferPtr, int RectHeight, int RectWidth,
; int BufferWidth, int Color);
;
.model small
.code
parms struc
dw ? ;pushed BP
dw ? ;pushed return address
BufferPtr dd ? ;far pointer to buffer in which to fill
RectHeight dw ? ;height of rectangle to fill
RectWidth dw ? ;width of rectangle to fill
BufferWidth dw ? ;width of buffer in which to fill
Color dw ? ;color with which to fill
parms ends
public -FillRect
-FillRectproc near
cld
push bp
mov bp,sp
push di
les di,[bp+BufferPtr]
mov dx,[bp+RectHeight]
mov bx,[bp+BufferWidth]
su bx,[bp+RectWidth] ;distance from end of one dest scan
; to start of next
mov al,byte ptr [bp+Color]
mov ah,al ;double the color for REP STOSW
RowLoop:
mov cx,[bp+RectWidth]
shr cx,1
rep stosw
adc cx,cx
rep stosb
add di,bx ;point to next scan to fill
dec dx ;count down rows to fill
jnz RowLoop
pop di
pop bp
ret
-FillRect endp
; Draws a masked image (a sprite) to the specified buffer. C-callable as:
; void DrawMasked(char far * BufferPtr, char * Pixels, char * Mask,
; int ImageHeight, int ImageWidth, int BufferWidth);
parms2 struc
dw ? ;pushed BP
dw ? ;pushed return address
BufferPtr2 dd ? ;far pointer to buffer in which to draw
Pixels dw ? ;pointer to image pixels
Mask dw ? ;pointer to image mask
ImageHeight dw ? ;height of image to draw
ImageWidth dw ? ;width of image to draw
BufferWidth2 dw ? ;width of buffer in which to draw
parms2 ends
public -DrawMasked
-DrawMasked proc near
cld
push bp
mov bp,sp
push si
push di
les di,[bp+BufferPtr2]
mov si,[bp+Mask]
mov bx,[bp+Pixels]
mov dx,[bp+ImageHeight]
mov ax,[bp+BufferWidth2]
su ax,[bp+ImageWidth] ;distance from end of one dest scan
mov [bp+BufferWidth2],ax ; to start of next
RowLoop2:
mov cx,[bp+ImageWidth]
ColumnLoop:
lods ;get the next mask byte
and al,al ;draw this pixel?
jz SkipPixel ;no
mov al,[bx] ;yes, draw the pixel
mov es:[di],al
SkipPixel:
inc bx ;point to next source pixel
inc d ;point to next dest pixel
dec cx
jnz ColumnLoop
add di,[bp+BufferWidth2] ;point to next scan to fill
dec dx ;count down rows to fill
jnz RowLoop2
pop di
pop si
pop bp
ret
-DrawMasked endp
; Copies a rectangle from one buffer to another. C-callable as:
; void CopyRect(DestBufferPtr, SrcBufferPtr, CopyHeight, CopyWidth,
; DestBufferWidth, SrcBufferWidth);
parms3 struc
dw ? ;pushed BP
dw ? ;pushed return address
DestBufferPtr dd ? ;far pointer to buffer to which to copy
SrcBufferPtr dd ? ;far pointer to buffer from which to copy
CopyHeight dw ? ;height of rect to copy
CopyWidth dw ? ;width of rect to copy
DestBufferWidth dw ? ;width of buffer to which to copy
SrcBufferWidth dw ? ;width of buffer from which to copy
parms3 ends
public -CopyRect
-CopyRect proc near
cld
push bp
mov bp,sp
push si
push di
push ds
les di,[bp+DestBufferPtr]
lds si,[bp+SrcBufferPtr]
mov dx,[bp+CopyHeight]
mov bx,[bp+DestBufferWidth] ;distance from end of one dest scan
su bx,[bp+CopyWidth] ; of copy to the next
mov ax,[bp+SrcBufferWidth] ;distance from end of one source scan
su ax,[bp+CopyWidth] ; of copy to the next
RowLoop3:
mov cx,[bp+CopyWidth] ;# of bytes to copy
shr cx,1
rep movsw ;copy as many words as possible
adc cx,cx
rep movs ;copy odd byte, if any
add si,ax ;point to next source scan line
add di,bx ;point to next dest scan line
dec dx ;count down rows to fill
jnz RowLoop3
pop ds
pop di
pop si
pop bp
ret
-CopyRect endp
end
</PRE>
<!-- END CODE //-->
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<font face="Verdana,sans-serif" size="1">Graphics Programming Black Book &copy; 2001 Michael Abrash</font>
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