| MEMDRAW(3) | MEMDRAW(3)

NAME

Memimage, Memdata, Memdrawparam, memimageinit, wordaddr, byteaddr, memimagemove, allocmemimage, allocmemimaged, readmemimage, creadmemimage, writememimage, freememimage, memsetchan, loadmemimage, cloadmemimage, unloadmemimage, memfillcolor, memarc, mempoly, memellipse, memfillpoly, memimageline, memimagedraw, drawclip, memlinebbox, memlineendsize, allocmemsubfont, openmemsubfont, freememsubfont, memsubfontwidth, getmemdefont, memimagestring, iprint, hwdraw – drawing routines for memory-resident images

SYNOPSIS

`#include <u.h>
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <memdraw.h>

` `typedef struct Memdata
{

| ulong *base; /* allocated data pointer */ uchar *bdata; /* first byte of actual data; word−aligned */ int ref; /* number of Memimages using this data */ void* imref; /* last image that pointed at this */ int allocd; /* is this malloc'd? */

} Memdata;
enum {

| Frepl = 1<<0, /* is replicated */ Fsimple = 1<<1, /* is 1x1 */ Fgrey = 1<<2, /* is grey */ Falpha = 1<<3, /* has explicit alpha */ Fcmap = 1<<4, /* has cmap channel */ Fbytes = 1<<5, /* has only 8−bit channels */

};
typedef struct Memimage
{

Rectangle r; /* rectangle in data area, local coords */
Rectangle clipr; /* clipping region */
int depth; /* number of bits of storage per pixel */
int nchan; /* number of channels */
ulong chan; /* channel descriptions */
Memdata *data; /* pointer to data */
int zero; /* data−>bdata+zero==&byte containing (0,0) */
ulong width; /* width in words of a single scan line */
Memlayer *layer; /* nil if not a layer*/
ulong flags;

`

| ...

`} Memimage;
typedef struct Memdrawparam
{

| Memimage *dst; Rectangle r; Memimage *src; Rectangle sr; Memimage *mask; Rectangle mr;

`

| ...

`} Memdrawparam;
int drawdebug;

` `void memimageinit(void)
ulong* wordaddr(Memimage *i, Point p)
uchar* byteaddr(Memimage *i, Point p)
void memimagemove(void *from, void *to)

Memimage* allocmemimage(Rectangle r, ulong chan)
Memimage* allocmemimaged(Rectangle r, ulong chan, Memdata *data)
Memimage* readmemimage(int fd)
Memimage* creadmemimage(int fd)
int writememimage(int fd, Memimage *i)
void freememimage(Memimage *i)
int memsetchan(Memimage*, ulong)

int loadmemimage(Memimage *i, Rectangle r,

| uchar *buf, int nbuf)

int cloadmemimage(Memimage *i, Rectangle r,

| uchar *buf, int nbuf)

int unloadmemimage(Memimage *i, Rectangle r,

| uchar *buf, int nbuf)

void memfillcolor(Memimage *i, ulong color)

void memarc(Memimage *dst, Point c, int a, int b, int thick,

| Memimage *src, Point sp, int alpha, int phi, Drawop op)

void mempoly(Memimage *dst, Point *p, int np, int end0,

| int end1, int radius, Memimage *src, Point sp, Drawop op)

void memellipse(Memimage *dst, Point c, int a, int b,

| int thick, Memimage *src, Point sp, Drawop op)

void memfillpoly(Memimage *dst, Point *p, int np, int wind,

| Memimage *src, Point sp, Drawop op)

void memimageline(Memimage *dst, Point p0, Point p1, int end0,

| int end1, int radius, Memimage *src, Point sp, Drawop op)

void memimagedraw(Memimage *dst, Rectangle r, Memimage *src,

Point sp, Memimage *mask, Point mp, Drawop op)

int drawclip(Memimage *dst, Rectangle *dr, Memimage *src,

| Point *sp, Memimage *mask, Point *mp, Rectangle *sr, Rectangle *mr)

Rectangle memlinebbox(Point p0, Point p1, int end0, int end1,

| int radius)

int memlineendsize(int end)

Memsubfont* allocmemsubfont(char *name, int n, int height,

| int ascent, Fontchar *info, Memimage *i)

Memsubfont* openmemsubfont(char *name)
void freememsubfont(Memsubfont *f)
Point memsubfontwidth(Memsubfont *f, char *s)
Memsubfont* getmemdefont(void)
Point memimagestring(Memimage *dst, Point p, Memimage *color,

Point cp, Memsubfont *f, char *cs, Drawop op)

int iprint(char *fmt, ...)
int hwdraw(Memdrawparam *param)
`

DESCRIPTION

The `Memimage` type defines memory-resident rectangular pictures and the methods to draw upon them; `Memimage`s differ from `Image`s (see draw(3)) in that they are manipulated directly in user memory rather than by RPCs to the `/dev/draw` hierarchy. The library is the basis for the kernel draw(3) driver and also used by a number of programs that must manipulate images without a display.

The `r, clipr`, `depth`, `nchan`, and `chan` structure elements are identical to the ones of the same name in the `Image` structure.

The `flags` element of the `Memimage` structure holds a number of bits of information about the image. In particular, it subsumes the purpose of the `repl` element of `Image` structures.

Memimageinit initializes various static data that the library depends on, as well as the replicated solid color images `memopaque`, `memtransparent`, `memblack`, and `memwhite`. It should be called before referring to any of these images and before calling any of the other library functions.

Each `Memimage` points at a `Memdata` structure that in turn points at the actual pixel data for the image. This allows multiple images to be associated with the same `Memdata`. The first word of the data pointed at by the `base` element of `Memdata` points back at the `Memdata` structure, so that in the Plan 9 kernel, the memory allocator (see Plan 9’s pool(3)) can compact image memory using memimagemove.

Because images can have different coordinate systems, the `zero` element of the `Memimage` structure contains the offset that must be added to the `bdata` element of the corresponding `Memdata` structure in order to yield a pointer to the data for the pixel (0,0). Adding `width` machine words to this pointer moves it down one scan line. The `depth` element can be used to determine how to move the pointer horizontally. Note that this method works even for images whose rectangles do not include the origin, although one should only dereference pointers corresponding to pixels within the image rectangle. Wordaddr and byteaddr perform these calculations, returning pointers to the word and byte, respectively, that contain the beginning of the data for a given pixel.

Allocmemimage allocages images with a given rectangle and channel descriptor (see `strtochan` in graphics(3)), creating a fresh `Memdata` structure and associated storage. Allocmemimaged is similar but uses the supplied Memdata structure rather than a new one. The readmemimage function reads an uncompressed bitmap from the given file descriptor, while creadmemimage reads a compressed bitmap. Writememimage writes a compressed representation of i to file descriptor fd. For more on bitmap formats, see image(7). Freememimage frees images returned by any of these routines. The `Memimage` structure contains some tables that are used to store precomputed values depending on the channel descriptor. Memsetchan updates the `chan` element of the structure as well as these tables, returning –1 if passed a bad channel descriptor.

Loadmemimage and cloadmemimage replace the pixel data for a given rectangle of an image with the given buffer of uncompressed or compressed data, respectively. When calling cloadmemimage, the buffer must contain an integral number of compressed chunks of data that exactly cover the rectangle. Unloadmemimage retrieves the uncompressed pixel data for a given rectangle of an image. All three return the number of bytes consumed on success, and –1 in case of an error.

Memfillcolor fills an image with the given color, a 32-bit number as described in color(3).

Memarc, mempoly, memellipse, memfillpoly, memimageline, and memimagedraw are identical to the arc, poly, ellipse, fillpoly, line, and gendraw, routines described in draw(3), except that they operate on `Memimage`s rather than `Image`s. Similarly, allocmemsubfont, openmemsubfont, freememsubfont, memsubfontwidth, getmemdefont, and memimagestring are the `Memimage` analogues of allocsubfont, openfont, freesubfont, strsubfontwidth, getdefont, and `string` (see subfont(3) and graphics(3)), except that they operate only on `Memsubfont`s rather than `Font`s.

Drawclip takes the images involved in a draw operation, together with the destination rectangle `dr` and source and mask alignment points `sp` and `mp`, and clips them according to the clipping rectangles of the images involved. It also fills in the rectangles `sr` and `mr` with rectangles congruent to the returned destination rectangle but translated so the upper left corners are the returned `sp` and `mp`. Drawclip returns zero when the clipped rectangle is empty. Memlinebbox returns a conservative bounding box containing a line between two points with given end styles and radius. Memlineendsize calculates the extra length added to a line by attaching an end of a given style.

The hwdraw and iprint functions are no-op stubs that may be overridden by clients of the library. Hwdraw is called at each call to memimagedraw with the current request’s parameters. If it can satisfy the request, it should do so and return 1. If it cannot satisfy the request, it should return 0. This allows (for instance) the kernel to take advantage of hardware acceleration. Iprint should format and print its arguments; it is given much debugging output when the global integer variable `drawdebug` is non-zero. In the kernel, iprint prints to a serial line rather than the screen, for obvious reasons.

SOURCE

| `/usr/local/plan9/src/libmemdraw`

SEE ALSO

| addpt(3), color(3), draw(3), graphics(3), memlayer(3), stringsize(3), subfont(3), color(7), utf(7)

BUGS

| Memimagestring is unusual in using a subfont rather than a font, and in having no parameter to align the source.