TH DRAW 2
SH NAME
Image, draw, gendraw, drawreplxy, drawrepl,
replclipr, line, poly, fillpoly, bezier, bezspline, fillbezier, fillbezspline, ellipse,
fillellipse, arc, fillarc, icossin, icossin2, border, string, stringn,
runestring, runestringn, stringbg, stringnbg, runestringbg,
runestringnbg, _string, ARROW, drawsetdebug \- graphics functions
de PB
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SH SYNOPSIS
de PB
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PB
#include <u.h>
#include <libc.h>
#include <draw.h>
PB
typedef
struct Image
{
Display *display; /* display holding data */
int id; /* id of system-held Image */
Rectangle r; /* rectangle in data area, local coords */
Rectangle clipr; /* clipping region */
ulong chan; /* pixel channel format descriptor */
int depth; /* number of bits per pixel */
int repl; /* flag: data replicates to tile clipr */
Screen *screen; /* 0 if not a window */
Image *next; /* next in list of windows */
} Image;
PB
typedef enum
{
/* Porter-Duff compositing operators */
Clear = 0,
sp 0.1
SinD = 8,
DinS = 4,
SoutD = 2,
DoutS = 1,
sp 0.1
S = SinD|SoutD,
SoverD = SinD|SoutD|DoutS,
SatopD = SinD|DoutS,
SxorD = SoutD|DoutS,
sp 0.1
D = DinS|DoutS,
DoverS = DinS|DoutS|SoutD,
DatopS = DinS|SoutD,
DxorS = DoutS|SoutD, /* == SxorD */
sp 0.1
Ncomp = 12,
} Drawop;
PB
PD 0
ta +\w'\fL 'u +\w'\fL 'u +6n +4n
void draw(Image *dst, Rectangle r, Image *src,
Image *mask, Point p)
PB
void drawop(Image *dst, Rectangle r, Image *src,
Image *mask, Point p, Drawop op)
PB
void gendraw(Image *dst, Rectangle r, Image *src, Point sp,
Image *mask, Point mp)
PB
void gendrawop(Image *dst, Rectangle r, Image *src, Point sp,
Image *mask, Point mp, Drawop op)
PB
int drawreplxy(int min, int max, int x)
PB
Point drawrepl(Rectangle r, Point p)
PB
void replclipr(Image *i, int repl, Rectangle clipr)
PB
void line(Image *dst, Point p0, Point p1, int end0, int end1,
int radius, Image *src, Point sp)
PB
void lineop(Image *dst, Point p0, Point p1, int end0, int end1,
int radius, Image *src, Point sp, Drawop op)
PB
void poly(Image *dst, Point *p, int np, int end0, int end1,
int radius, Image *src, Point sp)
PB
void polyop(Image *dst, Point *p, int np, int end0, int end1,
int radius, Image *src, Point sp, Drawop op)
PB
void fillpoly(Image *dst, Point *p, int np, int wind,
Image *src, Point sp)
PB
void fillpolyop(Image *dst, Point *p, int np, int wind,
Image *src, Point sp, Drawop op)
PB
int bezier(Image *dst, Point p0, Point p1, Point p2, Point p3,
int end0, int end1, int radius, Image *src, Point sp)
PB
int bezierop(Image *dst, Point p0, Point p1, Point p2, Point p3,
int end0, int end1, int radius, Image *src, Point sp,
Drawop op)
PB
int bezspline(Image *dst, Point *pt, int npt, int end0, int end1,
int radius, Image *src, Point sp)
PB
int bezsplineop(Image *dst, Point *pt, int npt, int end0, int end1,
int radius, Image *src, Point sp, Drawop op)
PB
int bezsplinepts(Point *pt, int npt, Point **pp)
PB
int fillbezier(Image *dst, Point p0, Point p1, Point p2, Point p3,
int w, Image *src, Point sp)
PB
int fillbezierop(Image *dst, Point p0, Point p1, Point p2, Point p3,
int w, Image *src, Point sp, Drawop op)
PB
int fillbezspline(Image *dst, Point *pt, int npt, int w,
Image *src, Point sp)
PB
int fillbezsplineop(Image *dst, Point *pt, int npt, int w,
Image *src, Point sp, Drawop op)
PB
void ellipse(Image *dst, Point c, int a, int b, int thick,
Image *src, Point sp)
PB
void ellipseop(Image *dst, Point c, int a, int b, int thick,
Image *src, Point sp, Drawop op)
PB
void fillellipse(Image *dst, Point c, int a, int b,
Image *src, Point sp)
PB
void fillellipseop(Image *dst, Point c, int a, int b,
Image *src, Point sp, Drawop op)
PB
void arc(Image *dst, Point c, int a, int b, int thick,
Image *src, Point sp, int alpha, int phi)
PB
void arcop(Image *dst, Point c, int a, int b, int thick,
Image *src, Point sp, int alpha, int phi, Drawop op)
PB
void fillarc(Image *dst, Point c, int a, int b, Image *src,
Point sp, int alpha, int phi)
PB
void fillarcop(Image *dst, Point c, int a, int b, Image *src,
Point sp, int alpha, int phi, Drawop op)
PB
void icossin(int deg, int *cosp, int *sinp)
PB
void icossin2(int x, int y, int *cosp, int *sinp)
PB
void border(Image *dst, Rectangle r, int i, Image *color, Point sp)
PB
void borderop(Image *dst, Rectangle r, int i, Image *color, Point sp,
Drawop op)
br
PB
Point string(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s)
PB
Point stringop(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, Drawop op)
PB
Point stringn(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, int len)
PB
Point stringnop(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, int len, Drawop op)
PB
Point runestring(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r)
PB
Point runestringop(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, Drawop op)
PB
Point runestringn(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, int len)
PB
Point runestringnop(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, int len, Drawop op)
PB
Point stringbg(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, Image *bg, Point bgp)
PB
Point stringbgop(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, Image *bg, Point bgp, Drawop op)
PB
Point stringnbg(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, int len, Image *bg, Point bgp)
PB
Point stringnbgop(Image *dst, Point p, Image *src, Point sp,
Font *f, char *s, int len, Image *bg, Point bgp, Drawop op)
PB
Point runestringbg(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, Image *bg, Point bgp)
PB
Point runestringbgop(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, Image *bg, Point bgp, Drawop op)
PB
Point runestringnbg(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, int len, Image *bg, Point bgp)
PB
Point runestringnbgop(Image *dst, Point p, Image *src, Point sp,
Font *f, Rune *r, int len, Image *bg, Point bgp, Drawop op)
PB
Point _string(Image *dst, Point p, Image *src,
Point sp, Font *f, char *s, Rune *r, int len,
Rectangle clipr, Image *bg, Point bgp, Drawop op)
PB
void drawsetdebug(int on)
PD
PB
enum
{
/* line ends */
Endsquare = 0,
Enddisc = 1,
Endarrow = 2,
Endmask = 0x1F
};
PB
#define ARROW(a, b, c) (Endarrow|((a)<<5)|((b)<<14)|((c)<<23))
SH DESCRIPTION
The
B Image
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
BR Image ;
no special operators are needed to draw on a window.
PP
TP 10
B r
The coordinates of the rectangle in the plane for which the
B Image
has defined pixel values.
It should not be modified after the image is created.
TP
B clipr
The clipping rectangle: operations that read or write
the image will not access pixels outside
BR clipr .
Frequently,
B clipr
is the same as
BR r ,
but it may differ; see in particular the discussion of
BR repl .
The clipping region may be modified dynamically using
I replclipr
RI ( q.v. ).
TP
B chan
The pixel channel format descriptor, as described in
IR image (6).
The value should not be modified after the image is created.
TP
B depth
The
number of bits per pixel in the picture;
it is identically
B chantodepth(chan)
(see
IR graphics (2))
and is provided as a convenience.
The value should not be modified after the image is created.
TP
B repl
A boolean value specifying whether the image is tiled to cover
the plane when used as a source for a drawing operation.
If
B repl
is zero, operations are restricted to the intersection of
B r
and
BR clipr .
If
B repl
is set,
B r
defines the tile to be replicated and
B clipr
defines the portion of the plane covered by the tiling, in other words,
B r
is replicated to cover
BR clipr ;
in such cases
B r
and
B clipr
are independent.
IP
For example, a replicated image with
B r
set to ((0,\ 0),\ (1,\ 1)) and
B clipr
set to ((0,\ 0),\ (100,\ 100)),
with the single pixel of
B r
set to blue,
behaves identically to an image with
B r
and
B clipr
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
RI ( q.v. ).
PP
Most of the drawing functions come in two forms:
a basic form, and an extended form that takes an extra
B Drawop
to specify a Porter-Duff compositing operator to use.
The basic forms assume the operator is
BR SoverD ,
which suffices for the vast majority of applications.
The extended forms are named by adding an
RB - op
suffix to the basic form.
Only the basic forms are listed below.
TP
BI draw( dst\fP,\fP\ r\fP,\fP\ src\fP,\fP\ mask\fP,\fP\ p )
I Draw
is the standard drawing function.
Only those pixels within the intersection of
IB dst ->r
and
IB dst ->clipr
will be affected;
I draw
ignores
IB dst ->repl\fR.
The operation proceeds as follows
(this is a description of the behavior, not the implementation):
RS
IP 1.
If
B repl
is set in
I src
or
IR mask ,
replicate their contents to fill
their clip rectangles.
IP 2.
Translate
I src
and
I mask
so
I p
is aligned with
IB r .min\fR.
IP 3.
Set
I r
to the intersection of
I r
and
IB dst ->r\fR.
IP 4.
Intersect
I r
with
IB src ->clipr\fR.
If
IB src ->repl
is false, also intersect
I r
with
IB src ->r\fR.
IP 5.
Intersect
I r
with
IB mask ->clipr\fR.
If
IB mask ->repl
is false, also intersect
I r
with
IB mask ->r\fR.
IP 6.
For each location in
IR r ,
combine the
I dst
pixel with the
I src
pixel using the alpha value
corresponding to the
I mask
pixel.
If the
I mask
has an explicit alpha channel, the alpha value
corresponding to the
I mask
pixel is simply that pixel's alpha channel.
Otherwise, the alpha value is the NTSC greyscale equivalent
of the color value, with white meaning opaque and black transparent.
In terms of the Porter-Duff compositing algebra,
I draw
replaces the
I dst
pixels with
RI ( src
in
IR mask )
over
IR dst .
(In the extended form,
``over'' is replaced by
IR op ).
RE
IP
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.
TP
\f5gendraw(\f2dst\fP, \f2r\fP, \f2src\fP, \f2p0\fP, \f2mask\fP, \f2p1\f5)\fP
Similar to
I draw
except that
I gendraw
aligns the source and mask differently:
I src
is aligned so
I p0
corresponds to
IB r .min
and
I mask
is aligned so
I p1
corresponds to
IB r .min .
For most purposes with simple masks and source images,
B draw
is sufficient, but
B gendraw
is the general operator and the one all other drawing primitives are built upon.
TP
BI drawreplxy( min , max , x\f5)
Clips
I x
to be in the half-open interval [\fImin\fP, \fImax\fP) by adding
or subtracting a multiple of \fImax-min\fP.
TP
BI drawrepl( r , p )
Clips the point \fIp\fP to be within the rectangle \fIr\fP
by translating the point horizontally by an integer multiple of rectangle width
and vertically by the height.
TP
BI replclipr( i , repl , clipr\f5)
Because the image data is stored on the server, local modifications to the
B Image
data structure itself will have no effect.
I Replclipr
modifies the local
B Image
data structure's
B repl
and
B clipr
fields, and notifies the server of their modification.
TP
\f5line(\f2dst\fP, \f2p0\fP, \f2p1\fP, \f2end0\fP, \f2end1\fP, \f2thick\fP, \f2src\fP, \f2sp\fP)
Line
draws in
I dst
a line of width
RI 1+2* thick
pixels joining points
I p0
and
IR p1 .
The line is drawn using pixels from the
I src
image aligned so
I sp
in the source corresponds to
I p0
in the destination.
The line touches both
I p0
and
IR p1 ,
and
I end0
and
I end1
specify how the ends of the line are drawn.
B Endsquare
terminates the line perpendicularly to the direction of the line; a thick line with
B Endsquare
on both ends will be a rectangle.
B Enddisc
terminates the line by drawing a disc of diameter
RI 1+2* thick
centered on the end point.
B Endarrow
terminates the line with an arrowhead whose tip touches the endpoint.
IP
The macro
B ARROW
permits explicit control of the shape of the arrow.
If all three parameters are zero, it produces the default arrowhead,
otherwise,
I a
sets the distance along line from end of the regular line to tip,
I b
sets the distance along line from the barb to the tip,
and
I c
sets the distance perpendicular to the line from edge of line to the tip of the barb,
all in pixels.
IP
I Line
and the other geometrical operators are equivalent to calls to
I gendraw
using a mask produced by the geometric procedure.
TP
\f5poly(\f2dst\fP, \f2p\fP, \f2np\fP, \f2end0\fP, \f2end1\fP, \f2thick\fP, \f2src\fP, \f2sp\fP)
I Poly
draws a general polygon; it
is conceptually equivalent to a series of calls to
I line
joining adjacent points in the
array of
B Points
IR p ,
which has
I np
elements.
The ends of the polygon are specified as in
IR line ;
interior lines are terminated with
B Enddisc
to make smooth joins.
The source is aligned so
I sp
corresponds to
IB p [0]\f1.
TP
\f5fillpoly(\f2dst\fP, \f2p\fP, \f2np\fP, \f2wind\fP, \f2src\fP, \f2sp\fP)
I Fillpoly
is like
I poly
but fills in the resulting polygon rather than outlining it.
The source is aligned so
I sp
corresponds to
IB p [0]\f1.
The winding rule parameter
I wind
resolves ambiguities about what to fill if the polygon is self-intersecting.
If
I wind
is
BR ~0 ,
a pixel is inside the polygon if the polygon's winding number about the point
is non-zero.
If
I wind
is
BR 1 ,
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.
TP
\f5bezier(\f2dst\fP, \f2a\fP, \f2b\fP, \f2c\fP, \f2d\fP, \f2end0\fP, \f2end1\fP, \f2thick\fP, \f2src\fP, \f2sp\fP)
I Bezier
draws the
cubic Bezier curve defined by
B Points
IR a ,
IR b ,
IR c ,
and
IR d .
The end styles are determined by
I end0
and
IR end1 ;
the thickness of the curve is
RI 1+2* thick .
The source is aligned so
I sp
in
I src
corresponds to
I a
in
IR dst .
TP
\f5bezspline(\f2dst\fP, \f2p\fP, \f2np\fP, \f2end0\fP, \f2end1\fP, \f2thick\fP, \f2src\fP, \f2sp\fP)
I Bezspline
takes the same arguments as
I poly
but draws a quadratic B-spline (despite its name) rather than a polygon.
If the first and last points in
I p
are equal, the spline has periodic end conditions.
TP
\f5bezsplinepts(\f2pt\fP, \f2npt\fP, \f2pp\fP)
I Bezsplinepts
returns in
I pp
a list of points making up the open polygon that
I bezspline
would draw.
The caller is responsible for freeing
IR *pp .
TP
\f5fillbezier(\f2dst\fP, \f2a\fP, \f2b\fP, \f2c\fP, \f2d\fP, \f2wind\fP, \f2src\fP, \f2sp\fP)
I Fillbezier
is to
I bezier
as
I fillpoly
is to
IR poly .
TP
\f5fillbezspline(\f2dst\fP, \f2p\fP, \f2wind\fP, \f2src\fP, \f2sp\fP)
I Fillbezspline
is like
I fillpoly
but fills the quadratic B-spline rather than the polygon outlined by
IR p .
The spline is closed with a line if necessary.
TP
\f5ellipse(\f2dst\fP, \f2c\fP, \f2a\fP, \f2b\fP, \f2thick\fP, \f2src\fP, \f2sp\fP)
I Ellipse
draws in
I dst
an ellipse centered on
I c
with horizontal and vertical semiaxes
I a
and
IR b .
The source is aligned so
I sp
in
I src
corresponds to
I c
in
IR dst .
The ellipse is drawn with thickness
RI 1+2* thick .
TP
\f5fillellipse(\f2dst\fP, \f2c\fP, \f2a\fP, \f2b\fP, \f2src\fP, \f2sp\fP)
I Fillellipse
is like
I ellipse
but fills the ellipse rather than outlining it.
TP
\f5arc(\f2dst\fP, \f2c\fP, \f2a\fP, \f2b\fP, \f2thick\fP, \f2src\fP, \f2sp\fP, \f2alpha\fP, \f2phi\fP)
I Arc
is like
IR ellipse ,
but draws only that portion of the ellipse starting at angle
I alpha
and extending through an angle of
IR phi .
The angles are measured in degrees counterclockwise from the positive
I x
axis.
TP
\f5fillarc(\f2dst\fP, \f2c\fP, \f2a\fP, \f2b\fP, \f2src\fP, \f2sp\fP, \f2alpha\fP, \f2phi\fP)
I Fillarc
is like
IR arc ,
but fills the sector with the source color.
TP
\f5icossin(\f2deg\fP, \f2cosp\fP, \f2sinp\fP)
I Icossin
stores in
BI * cosp
and
BI * sinp
scaled integers representing the cosine and sine of the angle
IR deg ,
measured in integer degrees.
The values are scaled so cos(0) is 1024.
TP
\f5icossin2(\f2x\fP, \f2y\fP, \f2cosp\fP, \f2sinp\fP)
I Icossin2
is analogous to
IR icossin,
with the angle represented not in degrees but implicitly by the point
RI ( x , y ).
It is to
I icossin
what
B atan2
is to
B atan
(see
IR sin (2)).
TP
BI border( dst\fP,\fP\ r\fP,\fP\ i\fP,\fP\ color\fP,\fP\ sp\fP)
I Border
draws an outline of rectangle
I r
in the specified
IR color .
The outline has width
IR i ;
if positive, the border goes inside the rectangle; negative, outside.
The source is aligned so
I sp
corresponds to
IB r .min .
TP
BI string( dst\fP,\fP\ p\fP,\fP\ src\fP,\fP\ sp\fP,\fP\ font\fP,\fP\ s )
I String
draws in
I dst
characters specified by the string
I s
and
IR font ;
it is equivalent to a series of calls to
I gendraw
using source
I src
and masks determined by the character shapes.
The text is positioned with the left of the first character at
IB p .x
and the top of the line of text at
IB p .y\f1.
The source is positioned so
I sp
in
I src
corresponds to
I p
in
IR dst .
I String
returns a
B Point
that is the position of the next character that would be drawn if the string were longer.
IP
For characters with undefined
or zero-width images in the font, the character at font position 0 (NUL) is drawn.
IP
The other string routines are variants of this basic form, and
have names that encode their variant behavior.
Routines whose names contain
B rune
accept a string of Runes rather than
SM UTF\c
-encoded bytes.
Routines ending in
B n
accept an argument,
IR n ,
that defines the number of characters to draw rather than accepting a NUL-terminated
string.
Routines containing
B bg
draw the background behind the characters in the specified color
RI ( bg )
and
alignment
RI ( bgp );
normally the text is drawn leaving the background intact.
IP
The routine
I _string
captures all this behavior into a single operator. Whether it draws a
SM UTF
string
or Rune string depends on whether
I s
or
I r
is null (the string length is always determined by
IR len ).
If
I bg
is non-null, it is used as a background color.
The
I clipr
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.
TP
BI drawsetdebug( on )
Turns on or off debugging output (usually
to a serial line) according to whether
I on
is non-zero.
SH SOURCE
B /sys/src/libdraw
SH SEE ALSO
IR graphics (2),
IR stringsize (2),
IR color (6),
IR utf (6),
IR addpt (2)
PP
T. Porter, T. Duff.
``Compositing Digital Images'',
I "Computer Graphics
(Proc. SIGGRAPH), 18:3, pp. 253-259, 1984.
SH DIAGNOSTICS
These routines call the graphics error function on fatal errors.
SH BUGS
Anti-aliased characters can be drawn by defining a font
with multiple bits per pixel, but there are
no anti-aliasing geometric primitives.
