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<title>draw(3) - Plan 9 from User Space</title>
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<tr><td width=20><td><b>DRAW(3)</b><td align=right><b>DRAW(3)</b>
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<p><font size=+1><b>NAME </b></font><br>
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Image, draw, drawop, gendraw, gendrawop, drawreplxy, drawrepl,
replclipr, line, lineop, poly, polyop, fillpoly, fillpolyop, bezier,
bezierop, bezspline, bezsplineop, bezsplinepts, fillbezier, fillbezierop,
fillbezspline, fillbezsplineop, ellipse, ellipseop, fillellipse,
fillellipseop, arc, arcop, fillarc, fillarcop, icossin, icossin2,
border, string, stringop, stringn, stringnop, runestring, runestringop,
runestringn, runestringnop, stringbg, stringbgop, stringnbg, stringnbgop,
runestringbg, runestringbgop, runestringnbg, runestringnbgop,
_string, ARROW, drawsetdebug &ndash; graphics functions<br>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>#include &lt;u.h&gt;<br>
#include &lt;libc.h&gt;<br>
#include &lt;draw.h&gt;<br>
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typedef<br>
struct Image<br>
{<br>
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Display &nbsp;&nbsp;&nbsp;&nbsp;*display; /* display holding data */<br>
int &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;id; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* id of system&#8722;held Image */<br>
Rectangle r; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* rectangle in data area, local coords */<br>
Rectangle clipr; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* clipping region */<br>
ulong &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;chan; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* pixel channel format descriptor */<br>
int &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;depth; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* number of bits per pixel */<br>
int &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;repl; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* flag: data replicates to tile clipr */<br>
Screen &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*screen; &nbsp;&nbsp;&nbsp;/* 0 if not a window */<br>
Image &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*next; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* next in list of windows */<br>
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} Image;<br>
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typedef enum<br>
{<br>
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/* Porter&#8722;Duff compositing operators */<br>
Clear &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= 0,<br>
SinD = 8,<br>
DinS = 4,<br>
SoutD &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= 2,<br>
DoutS &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= 1,<br>
S &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= SinD|SoutD,<br>
SoverD &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= SinD|SoutD|DoutS,<br>
SatopD &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= SinD|DoutS,<br>
SxorD &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= SoutD|DoutS,<br>
D &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= DinS|DoutS,<br>
DoverS &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= DinS|DoutS|SoutD,<br>
DatopS &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= DinS|SoutD,<br>
DxorS &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= DoutS|SoutD, /* == SxorD */<br>
Ncomp = 12,<br>
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} Drawop;<br>
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void &nbsp;&nbsp;&nbsp;draw(Image *dst, Rectangle r, Image *src,<br>
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Image *mask, Point p)<br>
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void &nbsp;&nbsp;&nbsp;drawop(Image *dst, Rectangle r, Image *src,<br>
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Image *mask, Point p, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;gendraw(Image *dst, Rectangle r, Image *src, Point sp,<br>
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Image *mask, Point mp)<br>
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void &nbsp;&nbsp;&nbsp;gendrawop(Image *dst, Rectangle r, Image *src, Point sp,<br>
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Image *mask, Point mp, Drawop op)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;drawreplxy(int min, int max, int x)<br>
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Point drawrepl(Rectangle r, Point p)<br>
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void &nbsp;&nbsp;&nbsp;replclipr(Image *i, int repl, Rectangle clipr)<br>
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void &nbsp;&nbsp;&nbsp;line(Image *dst, Point p0, Point p1, int end0, int end1,<br>
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int radius, Image *src, Point sp)<br>
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void &nbsp;&nbsp;&nbsp;lineop(Image *dst, Point p0, Point p1, int end0, int end1,<br>
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int radius, Image *src, Point sp, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;poly(Image *dst, Point *p, int np, int end0, int end1,<br>
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int radius, Image *src, Point sp)<br>
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void &nbsp;&nbsp;&nbsp;polyop(Image *dst, Point *p, int np, int end0, int end1,<br>
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int radius, Image *src, Point sp, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;fillpoly(Image *dst, Point *p, int np, int wind,<br>
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Image *src, Point sp)<br>
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void &nbsp;&nbsp;&nbsp;fillpolyop(Image *dst, Point *p, int np, int wind,<br>
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Image *src, Point sp, Drawop op)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;bezier(Image *dst, Point p0, Point p1, Point p2, Point p3,<br>
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int end0, int end1, int radius, Image *src, Point sp)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;bezierop(Image *dst, Point p0, Point p1, Point p2, Point p3,<br>
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int end0, int end1, int radius, Image *src, Point sp,<br>
Drawop op)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;bezspline(Image *dst, Point *pt, int npt, int end0, int end1,<br>
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int radius, Image *src, Point sp)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;bezsplineop(Image *dst, Point *pt, int npt, int end0, int
end1,<br>
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int radius, Image *src, Point sp, Drawop op)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;bezsplinepts(Point *pt, int npt, Point **pp)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;fillbezier(Image *dst, Point p0, Point p1, Point p2, Point
p3,<br>
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int w, Image *src, Point sp)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;fillbezierop(Image *dst, Point p0, Point p1, Point p2, Point
p3,<br>
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int w, Image *src, Point sp, Drawop op)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;fillbezspline(Image *dst, Point *pt, int npt, int w,<br>
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Image *src, Point sp)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;fillbezsplineop(Image *dst, Point *pt, int npt, int w,<br>
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Image *src, Point sp, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;ellipse(Image *dst, Point c, int a, int b, int thick,<br>
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Image *src, Point sp)<br>
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void &nbsp;&nbsp;&nbsp;ellipseop(Image *dst, Point c, int a, int b, int thick,<br>
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Image *src, Point sp, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;fillellipse(Image *dst, Point c, int a, int b,<br>
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Image *src, Point sp)<br>
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void &nbsp;&nbsp;&nbsp;fillellipseop(Image *dst, Point c, int a, int b,<br>
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Image *src, Point sp, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;arc(Image *dst, Point c, int a, int b, int thick,<br>
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Image *src, Point sp, int alpha, int phi)<br>
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void &nbsp;&nbsp;&nbsp;arcop(Image *dst, Point c, int a, int b, int thick,<br>
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Image *src, Point sp, int alpha, int phi, Drawop op)<br>
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void &nbsp;&nbsp;&nbsp;fillarc(Image *dst, Point c, int a, int b, Image *src,<br>
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Point sp, int alpha, int phi)<br>
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void &nbsp;&nbsp;&nbsp;fillarcop(Image *dst, Point c, int a, int b, Image *src,<br>
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Point sp, int alpha, int phi, Drawop op)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;icossin(int deg, int *cosp, int *sinp)<br>
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int &nbsp;&nbsp;&nbsp;&nbsp;icossin2(int x, int y, int *cosp, int *sinp)<br>
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void &nbsp;&nbsp;&nbsp;border(Image *dst, Rectangle r, int i, Image *color, Point
sp)<br>
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Point string(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, char *s)<br>
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Point stringop(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, char *s, Drawop op)<br>
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Point stringn(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, char *s, int len)<br>
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Point stringnop(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, char *s, int len, Drawop op)<br>
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Point runestring(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, Rune *r)<br>
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Point runestringop(Image *dst, Point p, Image *src, Point sp,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Font *f, Rune *r, Drawop op)<br>
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Point runestringn(Image *dst, Point p, Image *src, Point sp,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Font *f, Rune *r, int len)<br>
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Point runestringnop(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, Rune *r, int len, Drawop op)<br>
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Point stringbg(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, char *s, Image *bg, Point bgp)<br>
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Point stringbgop(Image *dst, Point p, Image *src, Point sp,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Font *f, char *s, Image *bg, Point bgp, Drawop op)<br>
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</table>
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Point stringnbg(Image *dst, Point p, Image *src, Point sp,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Font *f, char *s, int len, Image *bg, Point bgp)<br>
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Point stringnbgop(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, char *s, int len, Image *bg, Point bgp, Drawop op)<br>
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</table>
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Point runestringbg(Image *dst, Point p, Image *src, Point sp,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Font *f, Rune *r, Image *bg, Point bgp)<br>
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Point runestringbgop(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, Rune *r, Image *bg, Point bgp, Drawop op)<br>
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Point runestringnbg(Image *dst, Point p, Image *src, Point sp,<br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Font *f, Rune *r, int len, Image *bg, Point bgp)<br>
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</table>
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Point runestringnbgop(Image *dst, Point p, Image *src, Point sp,<br>
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Font *f, Rune *r, int len, Image *bg, Point bgp, Drawop op)<br>
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</table>
</table>
Point _string(Image *dst, Point p, Image *src,<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Point sp, Font *f, char *s, Rune *r, int len,<br>
Rectangle clipr, Image *bg, Point bgp, Drawop op)<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
</table>
</table>
void &nbsp;&nbsp;&nbsp;drawsetdebug(int on)<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
enum<br>
{<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
/* line ends */<br>
Endsquare &nbsp;&nbsp;&nbsp;= 0,<br>
Enddisc &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= 1,<br>
Endarrow = 2,<br>
Endmask &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;= 0x1F<br>
</table>
</table>
};<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
#define ARROW(a, b, c) (Endarrow|((a)&lt;&lt;5)|((b)&lt;&lt;14)|((c)&lt;&lt;23))<br>
</font></tt>
</table>
<p><font size=+1><b>DESCRIPTION </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <tt><font size=+1>Image</font></tt> type defines rectangular pictures and the methods to
draw upon them; it is also the building block for higher level
objects such as windows and fonts. In particular, a window is
represented as an <tt><font size=+1>Image</font></tt>; no special operators are needed to draw
on a window.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
<tt><font size=+1>r</font></tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The coordinates of the rectangle in the plane for which the <tt><font size=+1>Image</font></tt>
has defined pixel values. It should not be modified after the
image is created.<br>
<tt><font size=+1>clipr</font></tt>&nbsp;&nbsp;&nbsp;The clipping rectangle: operations that read or write the
image will not access pixels outside <tt><font size=+1>clipr</font></tt>. Frequently, <tt><font size=+1>clipr</font></tt>
is the same as <tt><font size=+1>r</font></tt>, but it may differ; see in particular the discussion
of <tt><font size=+1>repl</font></tt>. The clipping region may be modified dynamically using
<i>replclipr</i> (<i>q.v.</i>).<br>
<tt><font size=+1>chan</font></tt>&nbsp;&nbsp;&nbsp;&nbsp;The pixel channel format descriptor, as described in <a href="../man7/image.html"><i>image</i>(7)</a>.
The value should not be modified after the image is created.<br>
<tt><font size=+1>depth</font></tt>&nbsp;&nbsp;&nbsp;The number of bits per pixel in the picture; it is identically
<tt><font size=+1>chantodepth(chan)</font></tt> (see <a href="../man3/graphics.html"><i>graphics</i>(3)</a>) and is provided as a convenience.
The value should not be modified after the image is created.<br>
<tt><font size=+1>repl</font></tt>&nbsp;&nbsp;&nbsp;&nbsp;A boolean value specifying whether the image is tiled to cover
the plane when used as a source for a drawing operation. If <tt><font size=+1>repl</font></tt>
is zero, operations are restricted to the intersection of <tt><font size=+1>r</font></tt> and
<tt><font size=+1>clipr</font></tt>. If <tt><font size=+1>repl</font></tt> is set, <tt><font size=+1>r</font></tt> defines the tile to be replicated and
<tt><font size=+1>clipr</font></tt> defines the portion of the plane covered by the
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
tiling, in other words, <tt><font size=+1>r</font></tt> is replicated to cover <tt><font size=+1>clipr</font></tt>; in such
cases <tt><font size=+1>r</font></tt> and <tt><font size=+1>clipr</font></tt> are independent.<br>
For example, a replicated image with <tt><font size=+1>r</font></tt> set to ((0, 0), (1, 1))
and <tt><font size=+1>clipr</font></tt> set to ((0, 0), (100, 100)), with the single pixel of
<tt><font size=+1>r</font></tt> set to blue, behaves identically to an image with <tt><font size=+1>r</font></tt> and <tt><font size=+1>clipr</font></tt>
both set to ((0, 0), (100, 100)) and all pixels set to blue. However,
the first image requires far less memory. The
replication flag may be modified dynamically using <i>replclipr</i> (<i>q.v.</i>).
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
</table>
</table>
Most of the drawing functions come in two forms: a basic form,
and an extended form that takes an extra <tt><font size=+1>Drawop</font></tt> to specify a Porter-Duff
compositing operator to use. The basic forms assume the operator
is <tt><font size=+1>SoverD</font></tt>, which suffices for the vast majority of applications.
The extended forms are named by adding an
-<tt><font size=+1>op</font></tt> suffix to the basic form. Only the basic forms are listed
below.<br>
<tt><font size=+1>draw(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>r</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>mask</i><tt><font size=+1>,</font></tt> <i>p</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Draw</i> is the standard drawing function. Only those pixels within
the intersection of <i>dst</i><tt><font size=+1>&#8722;&gt;r</font></tt> and <i>dst</i><tt><font size=+1>&#8722;&gt;clipr</font></tt> will be affected; <i>draw</i>
ignores <i>dst</i><tt><font size=+1>&#8722;&gt;repl</font></tt>. The operation proceeds as follows (this is a
description of the behavior, not the implementation):<br>
1.&nbsp;&nbsp;&nbsp;&nbsp;If <tt><font size=+1>repl</font></tt> is set in <i>src</i> or <i>mask</i>, replicate their contents to fill
their clip rectangles.<br>
2.&nbsp;&nbsp;&nbsp;&nbsp;Translate <i>src</i> and <i>mask</i> so <i>p</i> is aligned with <i>r</i><tt><font size=+1>.min</font></tt>.<br>
3.&nbsp;&nbsp;&nbsp;&nbsp;Set <i>r</i> to the intersection of <i>r</i> and <i>dst</i><tt><font size=+1>&#8722;&gt;r</font></tt>.<br>
4.&nbsp;&nbsp;&nbsp;&nbsp;Intersect <i>r</i> with <i>src</i><tt><font size=+1>&#8722;&gt;clipr</font></tt>. If <i>src</i><tt><font size=+1>&#8722;&gt;repl</font></tt> is false, also intersect
<i>r</i> with <i>src</i><tt><font size=+1>&#8722;&gt;r</font></tt>.<br>
5.&nbsp;&nbsp;&nbsp;&nbsp;Intersect <i>r</i> with <i>mask</i><tt><font size=+1>&#8722;&gt;clipr</font></tt>. If <i>mask</i><tt><font size=+1>&#8722;&gt;repl</font></tt> is false, also intersect
<i>r</i> with <i>mask</i><tt><font size=+1>&#8722;&gt;r</font></tt>.<br>
6.&nbsp;&nbsp;&nbsp;&nbsp;For each location in <i>r</i>, combine the <i>dst</i> pixel with the <i>src</i> pixel
using the alpha value corresponding to the <i>mask</i> pixel. If the
<i>mask</i> has an explicit alpha channel, the alpha value corresponding
to the <i>mask</i> pixel is simply that pixel&#8217;s alpha channel. Otherwise,
the alpha value is the NTSC greyscale
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
equivalent of the color value, with white meaning opaque and black
transparent. In terms of the Porter-Duff compositing algebra,
<i>draw</i> replaces the <i>dst</i> pixels with (<i>src</i> in <i>mask</i>) over <i>dst</i>. (In
the extended form, &#8220;over&#8221; is replaced by <i>op</i>).<br>
</table>
The various pixel channel formats involved need not be identical.
If the channels involved are smaller than 8-bits, they will be
promoted before the calculation by replicating the extant bits;
after the calculation, they will be truncated to their proper
sizes.<br>
</table>
<tt><font size=+1>gendraw(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>r</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>p0</i><tt><font size=+1>,</font></tt> <i>mask</i><tt><font size=+1>,</font></tt> <i>p1</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Similar to <i>draw</i> except that <i>gendraw</i> aligns the source and mask
differently: <i>src</i> is aligned so <i>p0</i> corresponds to <i>r</i><tt><font size=+1>.min</font></tt> and <i>mask</i>
is aligned so <i>p1</i> corresponds to <i>r</i><tt><font size=+1>.min</font></tt><i>.</i> For most purposes with
simple masks and source images, <tt><font size=+1>draw</font></tt> is sufficient, but <tt><font size=+1>gendraw</font></tt>
is the general operator and the one all other
drawing primitives are built upon.<br>
</table>
<tt><font size=+1>drawreplxy(</font></tt><i>min</i><tt><font size=+1>,</font></tt><i>max</i><tt><font size=+1>,</font></tt><i>x</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Clips <i>x</i> to be in the half-open interval [<i>min</i>, <i>max</i>) by adding or
subtracting a multiple of <i>max-min</i>.<br>
</table>
<tt><font size=+1>drawrepl(</font></tt><i>r</i><tt><font size=+1>,</font></tt><i>p</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Clips the point <i>p</i> to be within the rectangle <i>r</i> by translating
the point horizontally by an integer multiple of rectangle width
and vertically by the height.<br>
</table>
<tt><font size=+1>replclipr(</font></tt><i>i</i><tt><font size=+1>,</font></tt><i>repl</i><tt><font size=+1>,</font></tt><i>clipr</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Because the image data is stored on the server, local modifications
to the <tt><font size=+1>Image</font></tt> data structure itself will have no effect. <i>Repclipr</i>
modifies the local <tt><font size=+1>Image</font></tt> data structure&#8217;s <tt><font size=+1>repl</font></tt> and <tt><font size=+1>clipr</font></tt> fields,
and notifies the server of their modification.<br>
</table>
<tt><font size=+1>line(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>p0</i><tt><font size=+1>,</font></tt> <i>p1</i><tt><font size=+1>,</font></tt> <i>end0</i><tt><font size=+1>,</font></tt> <i>end1</i><tt><font size=+1>,</font></tt> <i>thick</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Line draws in <i>dst</i> a line of width 1+2*<i>thick</i> pixels joining points
<i>p0</i> and <i>p1</i>. The line is drawn using pixels from the <i>src</i> image aligned
so <i>sp</i> in the source corresponds to <i>p0</i> in the destination. The
line touches both <i>p0</i> and <i>p1</i>, and <i>end0</i> and <i>end1</i> specify how the
ends of the line are drawn. <tt><font size=+1>Endsquare
</font></tt>terminates the line perpendicularly to the direction of the line;
a thick line with <tt><font size=+1>Endsquare</font></tt> on both ends will be a rectangle.
<tt><font size=+1>Enddisc</font></tt> terminates the line by drawing a disc of diameter 1+2*<i>thick</i>
centered on the end point. <tt><font size=+1>Endarrow</font></tt> terminates the line with an
arrowhead whose tip touches the endpoint.
The macro <tt><font size=+1>ARROW</font></tt> permits explicit control of the shape of the arrow.
If all three parameters are zero, it produces the default arrowhead,
otherwise, <i>a</i> sets the distance along line from end of the regular
line to tip, <i>b</i> sets the distance along line from the barb to the
tip, and <i>c</i> sets the distance perpendicular to the
line from edge of line to the tip of the barb, all in pixels.<br>
<i>Line</i> and the other geometrical operators are equivalent to calls
to <i>gendraw</i> using a mask produced by the geometric procedure.<br>
</table>
<tt><font size=+1>poly(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>p</i><tt><font size=+1>,</font></tt> <i>np</i><tt><font size=+1>,</font></tt> <i>end0</i><tt><font size=+1>,</font></tt> <i>end1</i><tt><font size=+1>,</font></tt> <i>thick</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Poly</i> draws a general polygon; it is conceptually equivalent to
a series of calls to <i>line</i> joining adjacent points in the array
of <tt><font size=+1>Points</font></tt> <i>p</i>, which has <i>np</i> elements. The ends of the polygon are
specified as in <i>line</i>; interior lines are terminated with <tt><font size=+1>Enddisc</font></tt>
to make smooth joins. The source is aligned so <i>sp
</i>corresponds to <i>p</i><tt><font size=+1>[0]</font></tt>.<br>
</table>
<tt><font size=+1>fillpoly(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>p</i><tt><font size=+1>,</font></tt> <i>np</i><tt><font size=+1>,</font></tt> <i>wind</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Fillpoly</i> is like <i>poly</i> but fills in the resulting polygon rather
than outlining it. The source is aligned so <i>sp</i> corresponds to
<i>p</i><tt><font size=+1>[0]</font></tt>. The winding rule parameter <i>wind</i> resolves ambiguities about
what to fill if the polygon is self-intersecting. If <i>wind</i> is <tt><font size=+1>~0</font></tt>,
a pixel is inside the polygon if the polygon&#8217;s winding number
about the point is non-zero. If <i>wind</i> is <tt><font size=+1>1</font></tt>, a pixel is inside if
the winding number is odd. Complementary values (0 or ~1) cause
outside pixels to be filled. The meaning of other values is undefined.
The polygon is closed with a line if necessary.<br>
</table>
<tt><font size=+1>bezier(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>a</i><tt><font size=+1>,</font></tt> <i>b</i><tt><font size=+1>,</font></tt> <i>c</i><tt><font size=+1>,</font></tt> <i>d</i><tt><font size=+1>,</font></tt> <i>end0</i><tt><font size=+1>,</font></tt> <i>end1</i><tt><font size=+1>,</font></tt> <i>thick</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Bezier</i> draws the cubic Bezier curve defined by <tt><font size=+1>Points</font></tt> <i>a</i>, <i>b</i>, <i>c</i>,
and <i>d</i>. The end styles are determined by <i>end0</i> and <i>end1</i>; the thickness
of the curve is 1+2*<i>thick</i>. The source is aligned so <i>sp</i> in <i>src</i>
corresponds to <i>a</i> in <i>dst</i>.<br>
</table>
<tt><font size=+1>bezspline(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>p</i><tt><font size=+1>,</font></tt> <i>end0</i><tt><font size=+1>,</font></tt> <i>end1</i><tt><font size=+1>,</font></tt> <i>thick</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Bezspline</i> takes the same arguments as <i>poly</i> but draws a quadratic
B-spline (despite its name) rather than a polygon. If the first
and last points in <i>p</i> are equal, the spline has periodic end conditions.<br>
</table>
<tt><font size=+1>bezsplinepts(</font></tt><i>pt</i><tt><font size=+1>,</font></tt> <i>npt</i><tt><font size=+1>,</font></tt> <i>pp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Bezsplinepts</i> returns in <i>pp</i> a list of points making up the open
polygon that <i>bezspline</i> would draw. The caller is responsible for
freeing <i>*pp</i>.<br>
</table>
<tt><font size=+1>fillbezier(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>a</i><tt><font size=+1>,</font></tt> <i>b</i><tt><font size=+1>,</font></tt> <i>c</i><tt><font size=+1>,</font></tt> <i>d</i><tt><font size=+1>,</font></tt> <i>wind</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Fillbezier</i> is to <i>bezier</i> as <i>fillpoly</i> is to <i>poly</i>.<br>
</table>
<tt><font size=+1>fillbezspline(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>p</i><tt><font size=+1>,</font></tt> <i>wind</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Fillbezspline</i> is like <i>fillpoly</i> but fills the quadratic B-spline
rather than the polygon outlined by <i>p</i>. The spline is closed with
a line if necessary.<br>
</table>
<tt><font size=+1>ellipse(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>c</i><tt><font size=+1>,</font></tt> <i>a</i><tt><font size=+1>,</font></tt> <i>b</i><tt><font size=+1>,</font></tt> <i>thick</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Ellipse</i> draws in <i>dst</i> an ellipse centered on <i>c</i> with horizontal
and vertical semiaxes <i>a</i> and <i>b</i>. The source is aligned so <i>sp</i> in
<i>src</i> corresponds to <i>c</i> in <i>dst</i>. The ellipse is drawn with thickness
1+2*<i>thick</i>.<br>
</table>
<tt><font size=+1>fillellipse(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>c</i><tt><font size=+1>,</font></tt> <i>a</i><tt><font size=+1>,</font></tt> <i>b</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Fillellipse</i> is like <i>ellipse</i> but fills the ellipse rather than
outlining it.<br>
</table>
<tt><font size=+1>arc(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>c</i><tt><font size=+1>,</font></tt> <i>a</i><tt><font size=+1>,</font></tt> <i>b</i><tt><font size=+1>,</font></tt> <i>thick</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>,</font></tt> <i>alpha</i><tt><font size=+1>,</font></tt> <i>phi</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Arc</i> is like <i>ellipse</i>, but draws only that portion of the ellipse
starting at angle <i>alpha</i> and extending through an angle of <i>phi</i>.
The angles are measured in degrees counterclockwise from the positive
<i>x</i> axis.<br>
</table>
<tt><font size=+1>fillarc(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>c</i><tt><font size=+1>,</font></tt> <i>a</i><tt><font size=+1>,</font></tt> <i>b</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>,</font></tt> <i>alpha</i><tt><font size=+1>,</font></tt> <i>phi</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Fillarc</i> is like <i>arc</i>, but fills the sector with the source color.<br>
</table>
<tt><font size=+1>icossin(</font></tt><i>deg</i><tt><font size=+1>,</font></tt> <i>cosp</i><tt><font size=+1>,</font></tt> <i>sinp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Icossin</i> stores in <tt><font size=+1>*</font></tt><i>cosp</i> and <tt><font size=+1>*</font></tt><i>sinp</i> scaled integers representing
the cosine and sine of the angle <i>deg</i>, measured in integer degrees.
The values are scaled so cos(0) is 1024.<br>
</table>
<tt><font size=+1>icossin2(</font></tt><i>x</i><tt><font size=+1>,</font></tt> <i>y</i><tt><font size=+1>,</font></tt> <i>cosp</i><tt><font size=+1>,</font></tt> <i>sinp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Icossin2</i> is analogous to <i>icossin,</i> with the angle represented not
in degrees but implicitly by the point (<i>x</i>,<i>y</i>). It is to <i>icossin</i>
what <tt><font size=+1>atan2</font></tt> is to <tt><font size=+1>atan</font></tt> (see <a href="../man3/sin.html"><i>sin</i>(3)</a>).<br>
</table>
<tt><font size=+1>border(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>r</i><tt><font size=+1>,</font></tt> <i>i</i><tt><font size=+1>,</font></tt> <i>color</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Border</i> draws an outline of rectangle <i>r</i> in the specified <i>color</i>.
The outline has width <i>i</i>; if positive, the border goes inside the
rectangle; negative, outside. The source is aligned so <i>sp</i> corresponds
to <i>r</i><tt><font size=+1>.min</font></tt><i>.<br>
</i>
</table>
<tt><font size=+1>string(</font></tt><i>dst</i><tt><font size=+1>,</font></tt> <i>p</i><tt><font size=+1>,</font></tt> <i>src</i><tt><font size=+1>,</font></tt> <i>sp</i><tt><font size=+1>,</font></tt> <i>font</i><tt><font size=+1>,</font></tt> <i>s</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>String</i> draws in <i>dst</i> characters specified by the string <i>s</i> and <i>font</i>;
it is equivalent to a series of calls to <i>gendraw</i> using source
<i>src</i> and masks determined by the character shapes. The text is
positioned with the left of the first character at <i>p</i><tt><font size=+1>.x</font></tt> and the
top of the line of text at <i>p</i><tt><font size=+1>.y</font></tt>. The source is positioned so <i>sp</i>
in
<i>src</i> corresponds to <i>p</i> in <i>dst</i>. <i>String</i> returns a <tt><font size=+1>Point</font></tt> that is the
position of the next character that would be drawn if the string
were longer.<br>
For characters with undefined or zero-width images in the font,
the character at font position 0 (NUL) is drawn.<br>
The other string routines are variants of this basic form, and
have names that encode their variant behavior. Routines whose
names contain <tt><font size=+1>rune</font></tt> accept a string of Runes rather than UTF-encoded
bytes. Routines ending in <tt><font size=+1>n</font></tt> accept an argument, <i>n</i>, that defines
the number of characters to draw rather than
accepting a NUL-terminated string. Routines containing <tt><font size=+1>bg</font></tt> draw
the background behind the characters in the specified color (<i>bg</i>)
and alignment (<i>bgp</i>); normally the text is drawn leaving the background
intact.<br>
The routine <i>_string</i> captures all this behavior into a single operator.
Whether it draws a UTF string or Rune string depends on whether
<i>s</i> or <i>r</i> is null (the string length is always determined by <i>len</i>).
If <i>bg</i> is non-null, it is used as a background color. The <i>clipr</i>
argument allows further management of clipping when
drawing the string; it is intersected with the usual clipping
rectangles to further limit the extent of the text.<br>
</table>
<tt><font size=+1>drawsetdebug(</font></tt><i>on</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Turns on or off debugging output (usually to a serial line) according
to whether <i>on</i> is non-zero.<br>
</table>
</table>
<p><font size=+1><b>SOURCE </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>/usr/local/plan9/src/libdraw<br>
</font></tt>
</table>
<p><font size=+1><b>SEE ALSO </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<a href="../man3/graphics.html"><i>graphics</i>(3)</a>, <a href="../man3/stringsize.html"><i>stringsize</i>(3)</a>, <a href="../man7/color.html"><i>color</i>(7)</a>, <a href="../man7/utf.html"><i>utf</i>(7)</a>, <a href="../man3/addpt.html"><i>addpt</i>(3)</a>
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
T. Porter, T. Duff. &#8220;Compositing Digital Images&#8221;, <i>Computer Graphics</i>
(Proc. SIGGRAPH), 18:3, pp. 253-259, 1984.<br>
</table>
<p><font size=+1><b>DIAGNOSTICS </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
These routines call the graphics error function on fatal errors.<br>
</table>
<p><font size=+1><b>BUGS </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Anti-aliased characters can be drawn by defining a font with multiple
bits per pixel, but there are no anti-aliasing geometric primitives.<br>
</table>
<td width=20>
<tr height=20><td>
</table>
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