dither.c

Intro/: Directory containing introductory examples. HelloWorld.c A simple program that draws a bo

#include <phigs.h>			/* get HP-PHIGS definitions for C */
#include <stdio.h>			/* get standard I/O definitions */

main()					/* file "Dither.c" */
{
    Pint	WorkstnID = 1;		/* workstation identifier */
    Pint	ConnID;			/* connection identifier */
    Pint	WorkstnType = POIDDX;	/* out/in, direct, dbl bfr, Xwindow */
    Pint	Structure = 1;		/* structure ID (chosen by user) */
    Pcolr_rep	Black, White;		/* reduce colourmap to monochrome */
    static Ptext_align TextAlignment = {PHOR_CTR, PVERT_TOP};
    Ppoint	TextLoc;		/* where is the text located? */
    Pgcolr	Colour;			/* colour of a particular tile */
    int		I, Row, Tile;		/* loop control variables */
    float	X, dX, Y;		/* for positioning tiles */
    int		Tiles, Level;		/* temporary variables */
    char	String[10];		/* for textual labels */

    popen_phigs((char *) stderr, 0);	/* errors go to "stderr" */
    pescape_u4("/dev/screen/phigs_window", &ConnID);
    popen_ws(WorkstnID, (void *) ConnID, WorkstnType);
    Black.rgb.red = Black.rgb.green = Black.rgb.blue = 0.0;   /* RGB: black */
    White.rgb.red = White.rgb.green = White.rgb.blue = 1.0;   /* RGB: white */
    pset_colr_rep(WorkstnID, 0, &Black);	/* colormap entry 0: black */
    for (I = 1; I <= 255; I++) {
	pset_colr_rep(WorkstnID, I, &White);	/* colormap entry I: white */
    }
    pescape_u250(WorkstnID, 0);		/* set colour environment */
    pescape_u240(WorkstnID, 16);	/* set dither cell size */
    /*---- define the structure ---------------------------------------------*/
    popen_struct(Structure);	
    pset_int_style(PSTYLE_SOLID);
    pset_char_ht(0.03);
    pset_text_align(&TextAlignment);
    Level = 0;				/* start with 0% gray (black) */
    for (Row = 1; Row <= 3; Row++) {
	Tiles = 6;			/* usually six tiles per row */
	dX = 0.0;			/* usually not shifted right */
	if (Row == 2) {			/* however, in row two... */
	    Tiles = 5;			/* ...there are only 5 tiles, */
	    dX = 0.085;			/* ...shifted right a tad. */
	}
	for (Tile = 1; Tile <= Tiles; Tile++) {
	    X = 0.17 * (Tile - 1) + dX;	/* define left edge */
	    Y = 1.2 - Row * 0.3;	/* define top edge */
	    Colour.colr_type = PCOLR_RGB;
	    Colour.colr_value.colr_rep.rgb.red   = Level/16.0;
	    Colour.colr_value.colr_rep.rgb.green = Level/16.0;
	    Colour.colr_value.colr_rep.rgb.blue  = Level/16.0;
	    pset_int_colr(&Colour);
	    DoRectangle(X, Y, X + 0.15, Y - 0.15);	/* define the tile */
	    sprintf(String, "%d/16", Level);
	    TextLoc.x = X + 0.075;
	    TextLoc.y = Y - 0.16;
	    ptext(&TextLoc, String);	/* print the label */
	    Level = Level + 1;		/* a little lighter next time */
	}
    }
    pclose_struct();
    ppost_struct(WorkstnID, Structure, 1.0);
    pupd_ws(WorkstnID, PFLAG_PERFORM);	/* (regeneration flag) */
    pclose_ws(WorkstnID);
    pclose_phigs();
}
/****************************************************************************/
DoRectangle(X1, Y1, X2, Y2)	/* define rectangle */
float	X1, Y1;			/* first corner of rectangle */
float	X2, Y2;			/* last corner of rectangle */
{    
    Ppoint	TilePts[5];		/* holding the geometry of the tile */
    Ppoint_list	Tile;			/* includes number of points */
    
    TilePts[0].x = X1, TilePts[0].y = Y1;	/* lower left corner */
    TilePts[1].x = X2, TilePts[1].y = Y1;	/* lower right corner */
    TilePts[2].x = X2, TilePts[2].y = Y2;	/* upper right corner */
    TilePts[3].x = X1, TilePts[3].y = Y2;	/* upper left corner */
    TilePts[4].x = X1, TilePts[4].y = Y1;	/* for polyline's sake */
    Tile.num_points = 4;
    Tile.points = TilePts;
    pfill_area(&Tile);			/* fill area */
    Tile.num_points = 5;		/* \ polyline is needed because */
    ppolyline(&Tile);			/* / pfill_area doesn't do edges */
}