Enhanced Graphics Adapter toolbox in TURBO pascal:

Authors: Frank Guenther (compuserve 76545,666)
Steve Olson

date : Dec 2 1985

Contact at "The Programmer's Toolbox"
(301) 540-7230 (data)

************************************
These functions and procedures are
in the public domain.
************************************

This file: egatool.arc, should yield three files;

ega.doc : This file
egatools.pas: Turbo pascal toolbox for the EGA;
setpal.pas : Program that will change the EGA palette from command
line arguments.

The following procedures and functions are included in the toolbox.

procedure writestr(string,col,row,color);
Writes a string at the specified column and row coordinates in color

procedure egaset(mode);
Sets the ega card to the specified mode (16=hi res);

procedure setmode(mode);
Sets the ega card to the specified read/write mode.

procedure setpalette(palette,color);
Sets the palette to the specified color value (0-63);

procedure egainfo;
Returns information abount the ega card in th following variables:
ega_mode : The current mode of the ega card;
ega_mem : The amount of memory available to the ega card.
ega_feature : The current setting of the feature bits.
ega_switch : The current switch setting of the ega.

procedure hrpixel(x,y,color);
Sets the pixel at the x and y coordinate to color;

function getpixval(x,y):integer;
Returns the color of pixel x:y.

function readpix(x,y,color):integer;
Returns the bitmask in the high order byte and the pixel flags in the
low order byte. Used by the testpix and findpix procedures.

function testpix(x,y,color):boolean;
Returns true if the x:y pixel is the specified color. It returns false
if its another color.

function findpix(x,y,color):integer;
Returns zero if the x:y pixel is the specified color, returns the
x offset if there is a pixel of the specified color in the same
byte as the x:y pixel. Example: pixel 100:100 is blue, if you
query pixel 96:100 for blue the returned value will be 4. Thus
you can calculate the nearest pixel by adding the return value
to x. It returns -99 if no pixel is found matching the color.

procedure hrclear(color);
Clears the screen to the specified color palette.

procedure hrline(x,y,x2,y2,color);
draws a line from x:y to x2:y2 inthe specified color.

procedure drawbox(x,y,x2,y2,color);
The coordinates x:y and x2:y2 define opposite corners of the box.

procedure fillbox(x,y,x2,y2,color);
Fills the defined box with the specified color.

procedure xorbox(x,y,x2,y2,xorvalue);
Inverts the color within the defined box. Succesive xor's will return
the original screen. The variable xorvalue should be $F or $7 to get
the best results. Used in conjuction with setpalette, you can change
the color to anything you want.

procedure xorstring(col,row,length);
Inverts the text at the defined row and column. Length is the length
of the text to invert.

procedure drawcircle(x,y,radius,color,flags);
Draws a circle at x:y of the specified color and radius. The flags
variable specifies the amount of the circle to be drawn.
$FF= full cicle
$0F= half circle (top);
$F0= half circle (bottom);
$3C= half circle (left);
$C3= half circle (right);
$03= quarter circle (top,left);
$08= eighth of a circle.

procedure palette;
Displays the default palette of the screen in 16 squares.

procedure interact;
Accepts the left and right arrow keys to choose a palette.
Accepts the up and down arrow keys to alter the palette.
Use ESC to exit the procedure.

The file egatools will compile into a demostration program that displays
the current palette and allows input of the arrow keys to choose and
alter a palette. The palette values will then be displayed.

The file setpal will compile into a program which will alter a number of
palettes to user specified values. The format of the command line arguments
are:

setpal NN:MM .... where nn=palette number and mm=value.
setpal 0:3 7:1 sets background to cyan and forground to blue.

Further information on the ega can be found in BYTE 10(11) 1985 page 209
or IBM Personal Computer Seminar Proceedings volume 2, number 11-1 (1985)

enjoy....