Use backtick code blocks for syntax highlighting
This commit is contained in:
James Gregory
parent
8ed9dea394
commit
f658bfbb40
203 changed files with 26546 additions and 25801 deletions
200
42-04.md
200
42-04.md
|
|
@ -12,72 +12,74 @@ pages: 784-787
|
|||
|
||||
**LISTING 42.4 L42-4.C**
|
||||
|
||||
/* Function to draw a non-antialiased line from (X0,Y0) to (X1,Y1), using a
|
||||
* simple fixed-point error accumulation approach.
|
||||
* Tested with Borland C++ in C compilation mode and the small model.
|
||||
*/
|
||||
extern void DrawPixel(int, int, int);
|
||||
```c
|
||||
/* Function to draw a non-antialiased line from (X0,Y0) to (X1,Y1), using a
|
||||
* simple fixed-point error accumulation approach.
|
||||
* Tested with Borland C++ in C compilation mode and the small model.
|
||||
*/
|
||||
extern void DrawPixel(int, int, int);
|
||||
|
||||
/* Non-antialiased line drawer.
|
||||
* (X0,Y0),(X1,Y1) = line to draw, Color = color in which to draw
|
||||
*/
|
||||
void DrawLine(int X0, int Y0, int X1, int Y1, int Color)
|
||||
{
|
||||
unsigned long ErrorAcc, ErrorAdj;
|
||||
int DeltaX, DeltaY, XDir, Temp;
|
||||
/* Non-antialiased line drawer.
|
||||
* (X0,Y0),(X1,Y1) = line to draw, Color = color in which to draw
|
||||
*/
|
||||
void DrawLine(int X0, int Y0, int X1, int Y1, int Color)
|
||||
{
|
||||
unsigned long ErrorAcc, ErrorAdj;
|
||||
int DeltaX, DeltaY, XDir, Temp;
|
||||
|
||||
/* Make sure the line runs top to bottom */
|
||||
if (Y0 > Y1) {
|
||||
Temp = Y0; Y0 = Y1; Y1 = Temp;
|
||||
Temp = X0; X0 = X1; X1 = Temp;
|
||||
}
|
||||
DrawPixel(X0, Y0, Color); /* draw the initial pixel */
|
||||
if ((DeltaX = X1 - X0) >= 0) {
|
||||
XDir = 1;
|
||||
} else {
|
||||
XDir = -1;
|
||||
DeltaX = -DeltaX; /* make DeltaX positive */
|
||||
}
|
||||
if ((DeltaY = Y1 - Y0) == 0) /* done if only one point in the line */
|
||||
if (DeltaX == 0) return;
|
||||
/* Make sure the line runs top to bottom */
|
||||
if (Y0 > Y1) {
|
||||
Temp = Y0; Y0 = Y1; Y1 = Temp;
|
||||
Temp = X0; X0 = X1; X1 = Temp;
|
||||
}
|
||||
DrawPixel(X0, Y0, Color); /* draw the initial pixel */
|
||||
if ((DeltaX = X1 - X0) >= 0) {
|
||||
XDir = 1;
|
||||
} else {
|
||||
XDir = -1;
|
||||
DeltaX = -DeltaX; /* make DeltaX positive */
|
||||
}
|
||||
if ((DeltaY = Y1 - Y0) == 0) /* done if only one point in the line */
|
||||
if (DeltaX == 0) return;
|
||||
|
||||
ErrorAcc = 0x8000; /* initialize line error accumulator to .5, so we can
|
||||
advance when we get halfway to the next pixel */
|
||||
/* 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 */
|
||||
ErrorAdj = ((((unsigned long)DeltaX << 17) / (unsigned long)DeltaY) +
|
||||
1) >> 1;
|
||||
/* Draw all pixels between the first and last */
|
||||
do {
|
||||
ErrorAcc += ErrorAdj; /* calculate error for this pixel */
|
||||
if (ErrorAcc & ~0xFFFFL) {
|
||||
/* The error accumulator turned over, so advance the X coord */
|
||||
X0 += XDir;
|
||||
ErrorAcc &= 0xFFFFL; /* clear integer part of result */
|
||||
}
|
||||
Y0++; /* Y-major, so always advance Y */
|
||||
DrawPixel(X0, Y0, Color);
|
||||
} while (--DeltaY);
|
||||
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 */
|
||||
ErrorAdj = ((((unsigned long)DeltaY << 17) / (unsigned long)DeltaX) +
|
||||
1) >> 1;
|
||||
/* Draw all remaining pixels */
|
||||
do {
|
||||
ErrorAcc += ErrorAdj; /* calculate error for this pixel */
|
||||
if (ErrorAcc & ~0xFFFFL) {
|
||||
/* The error accumulator turned over, so advance the Y coord */
|
||||
Y0++;
|
||||
ErrorAcc &= 0xFFFFL; /* clear integer part of result */
|
||||
}
|
||||
X0 += XDir; /* X-major, so always advance X */
|
||||
DrawPixel(X0, Y0, Color);
|
||||
} while (--DeltaX);
|
||||
}
|
||||
ErrorAcc = 0x8000; /* initialize line error accumulator to .5, so we can
|
||||
advance when we get halfway to the next pixel */
|
||||
/* 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 */
|
||||
ErrorAdj = ((((unsigned long)DeltaX << 17) / (unsigned long)DeltaY) +
|
||||
1) >> 1;
|
||||
/* Draw all pixels between the first and last */
|
||||
do {
|
||||
ErrorAcc += ErrorAdj; /* calculate error for this pixel */
|
||||
if (ErrorAcc & ~0xFFFFL) {
|
||||
/* The error accumulator turned over, so advance the X coord */
|
||||
X0 += XDir;
|
||||
ErrorAcc &= 0xFFFFL; /* clear integer part of result */
|
||||
}
|
||||
Y0++; /* Y-major, so always advance Y */
|
||||
DrawPixel(X0, Y0, Color);
|
||||
} while (--DeltaY);
|
||||
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 */
|
||||
ErrorAdj = ((((unsigned long)DeltaY << 17) / (unsigned long)DeltaX) +
|
||||
1) >> 1;
|
||||
/* Draw all remaining pixels */
|
||||
do {
|
||||
ErrorAcc += ErrorAdj; /* calculate error for this pixel */
|
||||
if (ErrorAcc & ~0xFFFFL) {
|
||||
/* The error accumulator turned over, so advance the Y coord */
|
||||
Y0++;
|
||||
ErrorAcc &= 0xFFFFL; /* clear integer part of result */
|
||||
}
|
||||
X0 += XDir; /* X-major, so always advance X */
|
||||
DrawPixel(X0, Y0, Color);
|
||||
} while (--DeltaX);
|
||||
}
|
||||
```
|
||||
|
||||
Listing 42.1 isn't particularly fast, because it calls **DrawPixel()**
|
||||
for each pixel. On the other hand, **DrawPixel()** makes it easy to try
|
||||
|
|
@ -95,46 +97,48 @@ drawn with a ruler.
|
|||
|
||||
**LISTING 42.5 L42-5.C**
|
||||
|
||||
/* Mode set and pixel-drawing functions for the 640x480 256-color mode of
|
||||
* Tseng Labs ET4000-based SuperVGAs.
|
||||
* Tested with Borland C++ in C compilation mode and the small model.
|
||||
*/
|
||||
#include <dos.h>
|
||||
```c
|
||||
/* Mode set and pixel-drawing functions for the 640x480 256-color mode of
|
||||
* Tseng Labs ET4000-based SuperVGAs.
|
||||
* Tested with Borland C++ in C compilation mode and the small model.
|
||||
*/
|
||||
#include <dos.h>
|
||||
|
||||
/* Screen dimension globals, used in main program to scale */
|
||||
int ScreenWidthInPixels = 640;
|
||||
int ScreenHeightInPixels = 480;
|
||||
/* Screen dimension globals, used in main program to scale */
|
||||
int ScreenWidthInPixels = 640;
|
||||
int ScreenHeightInPixels = 480;
|
||||
|
||||
/* ET4000 640x480 256-color draw pixel function. */
|
||||
void DrawPixel(int X, int Y, int Color)
|
||||
{
|
||||
#define SCREEN_SEGMENT 0xA000
|
||||
#define GC_SEGMENT_SELECT 0x3CD /* ET4000 segment (bank) select reg */
|
||||
unsigned char far *ScreenPtr;
|
||||
unsigned int Bank;
|
||||
unsigned long BitmapAddress;
|
||||
/* ET4000 640x480 256-color draw pixel function. */
|
||||
void DrawPixel(int X, int Y, int Color)
|
||||
{
|
||||
#define SCREEN_SEGMENT 0xA000
|
||||
#define GC_SEGMENT_SELECT 0x3CD /* ET4000 segment (bank) select reg */
|
||||
unsigned char far *ScreenPtr;
|
||||
unsigned int Bank;
|
||||
unsigned long BitmapAddress;
|
||||
|
||||
/* full bitmap address of pixel, as measured from address 0 to 0xFFFFF */
|
||||
BitmapAddress = (unsigned long) Y * ScreenWidthInPixels + X;
|
||||
/* Bank # is upper word of bitmap addr */
|
||||
Bank = BitmapAddress >> 16;
|
||||
/* Upper nibble is read bank #, lower nibble is write bank # */
|
||||
outp(GC_SEGMENT_SELECT, (Bank << 4) | Bank);
|
||||
/* Draw into the bank */
|
||||
FP_SEG(ScreenPtr) = SCREEN_SEGMENT;
|
||||
FP_OFF(ScreenPtr) = (unsigned int) BitmapAddress;
|
||||
*ScreenPtr = Color;
|
||||
}
|
||||
/* full bitmap address of pixel, as measured from address 0 to 0xFFFFF */
|
||||
BitmapAddress = (unsigned long) Y * ScreenWidthInPixels + X;
|
||||
/* Bank # is upper word of bitmap addr */
|
||||
Bank = BitmapAddress >> 16;
|
||||
/* Upper nibble is read bank #, lower nibble is write bank # */
|
||||
outp(GC_SEGMENT_SELECT, (Bank << 4) | Bank);
|
||||
/* Draw into the bank */
|
||||
FP_SEG(ScreenPtr) = SCREEN_SEGMENT;
|
||||
FP_OFF(ScreenPtr) = (unsigned int) BitmapAddress;
|
||||
*ScreenPtr = Color;
|
||||
}
|
||||
|
||||
/* ET4000 640x480 256-color mode-set function. */
|
||||
void SetMode()
|
||||
{
|
||||
union REGS regset;
|
||||
/* ET4000 640x480 256-color mode-set function. */
|
||||
void SetMode()
|
||||
{
|
||||
union REGS regset;
|
||||
|
||||
/* Set to 640x480 256-color graphics mode */
|
||||
regset.x.ax = 0x002E;
|
||||
int86(0x10, ®set, ®set);
|
||||
}
|
||||
/* Set to 640x480 256-color graphics mode */
|
||||
regset.x.ax = 0x002E;
|
||||
int86(0x10, ®set, ®set);
|
||||
}
|
||||
```
|
||||
|
||||
Listing 42.1 requires that the DAC palette be set up so that a
|
||||
**NumLevel**-long block of palette entries contains linearly decreasing
|
||||
|
|
|
|||
Loading…
Reference in a new issue