BITBLT(2G) BITBLT(2G)
NAME
bitblt, bitbltclip, clipline, point, segment, arc, circle,
disc, ellipse, texture, border, string, strsize, strwidth,
Fcode - graphics functions
SYNOPSIS
#include <u.h>
#include <libg.h>
void bitblt(Bitmap *db, Point dp, Bitmap *sb,
Rectangle sr, Fcode f)
void bitbltclip(void *)
int clipline(Rectangle r, Point *p0, Point *p1)
void point(Bitmap *b, Point p, int v, Fcode f)
void segment(Bitmap *b, Point p, Point q, int v, Fcode f)
void circle(Bitmap *b, Point p, int r, int v, Fcode f)
void disc(Bitmap *b, Point p, int r, int v, Fcode)
void arc(Bitmap *b, Point p0, Point p1, Point p2, int v, Fcode f)
void ellipse(Bitmap *b, Point p, int a, int b, int v, Fcode f)
void texture(Bitmap *b, Rectangle r, Bitmap *t, Fcode f)
void border(Bitmap *b, Rectangle r, int w, Fcode f)
Point string(Bitmap *b, Point p, Font *ft, char *s, Fcode f)
Point strsize(Font *ft, char *s)
long strwidth(Font *ft, char *s)
enum Fcode {
Zero, DnorS, DandnotS, notS,
notDandS, notD, DxorS, DnandS,
DandS, DxnorS, D, DornotS,
S, notDorS, DorS, F,
} Fcode;
DESCRIPTION
Bitblt (bit-block transfer) takes bits from rectangle sr in
the source Bitmap sb and overlays them on a congruent rect-
angle with the min corner at point dp in the destination
bitmap, db. The f parameter defines each destination pixel
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BITBLT(2G) BITBLT(2G)
as a function of the source and destination pixels. The
sixteen codes in Fcode give all possible boolean operations
on the source S and destination D. The code values may be
expressed as boolean operations on the values S and D. For
example, D|S computes the result as the logical or of the
destination pixel's old value and the overlaying source
pixel's value. If pixels are more than one bit deep, the
operations are bitwise. The Zero and F codes result in new
pixel values that are all zeros or all ones, respectively.
If the source and destination bitmaps have different depths,
the source rectangle is first converted to have the same
depth as the destination, as follows: conversion to a
smaller number of bits per pixel is accomplished by taking
the desired number of high order bits; conversion to a
larger number of bits per pixel is accomplished by putting
the small value into the high order bits, and replicating it
as many times as necessary to fill the lower order bits.
All of the drawing graphics functions clip the rectangle
against the source and destination bitmaps, so that only
pixels within the destination bitmap are changed and none
are changed that would have come from areas outside the
source bitmap. Bitbltclip takes a pointer to the first
argument of a bitblt argument list and clips dp and sr so
the resulting bitblt is confined to the source and destina-
tion bitmaps.
Point changes the value of the destination point p in bitmap
b according to function code f. The source is a pixel with
value v. The constant ~0 represents the maximum pixel value.
Segment, circle, disc, and ellipse all draw in bitmap b with
function code f and a source pixel with value v. Arc draws a
circular arc centered on p0, traveling clockwise from p1 to
p2 or a point on the circle near p2. Segment draws a line
segment in bitmap b from point p to q. The segment is half-
open: p is the first point of the segment and q is the first
point beyond the segment, so adjacent segments sharing end-
points abut. Clipline clips the line segment from *p0 to
*p1 (p0 is closed, p1 is open) to rectangle r, adjusting p0
and p1 so that the segment is within the rectangle and *p1
is closed. It returns 0 if none of the segment is in the
rectangle, 1 otherwise.
Circle draws a circle with radius r and center at point p.
Disc is the same except that it fills the circle. Ellipse
draws an ellipse with horizontal semi-axis a and vertical
semi-axis b.
Border draws, with function f in bitmap b, the rectangular
outline with lines of width w fitting just inside rectangle
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BITBLT(2G) BITBLT(2G)
r.
Texture draws, with function f in bitmap b, a texture using
the bitmap specified by t. The texture bitmap is aligned on
b's coordinate system so that (0,0) in both coordinate sys-
tems coincide, and then t is replicated to form a tiling of
b. The tiling is clipped to rectangle r in b, and then
transferred to b using the specified function.
String draws the text characters given by the null-
terminated UTF string s into bitmap b, using font ft. The
upper left corner of the first character (i.e., a point that
is ft->ascent above the baseline) is placed at point p, and
subsequent characters are placed on the same baseline, dis-
placed to the right by the previous character's width. The
individual characters are bitblt'ed into the destination,
using drawing function f. String returns the point after the
final character of s; this can be outside b if the string
was clipped.
The bounding box for text to be drawn with string in font ft
can be found with strsize; it returns the max point of the
bounding box, assuming a min point of (0,0). Strwidth
returns the x-component of the max point.
SEE ALSO
graphics(2), utf(6)
DIAGNOSTICS
These routines call the graphics error function on fatal
errors.
Page 3 Plan 9 (printed 11/17/24)