NAME

FdpicPreEncodeScanline − start encoding a fast disk picture file
FdpicEncodeScanline − encode a picture scanline
FdpicPostEncodeScanline − sequential encoding of a tile to disk

SYNOPSIS

#include <fdpicio.h>

FdpicPreEncodeScanline(channel,tilenumber)
PFILE ∗channel;
long tilenumber;

char ∗
FdpicEncodeScanline(channel, ptr)
PFILE ∗channel;
RGBAPixelType ∗ptr;

FdpicPostEncodeScanline(channel)
PFILE ∗channel;

DESCRIPTION

These routines are offered as an alternative to the FdPicWriteBuffer routine, described elsewhere, which converts one entire tile from memory buffer to disk.  These routines allow the sequential encoding of individual scanlines of a tile from a scanline memory buffer to disk.  These routines are fragile in the sense that the described order must be followed exactly to produce a correctly encoded picture on disk.  If a tile has width w and height h, there should be a RGBAPixelType buffer of w pixels.  There should be one call to FdpicPreEncodeScanline, h calls to FdpicEncodeScanline, and one call to FdpicPostEncodeScanline. 

FdpicPreEncodeScanline initiates the encoding of a tile and associates the encoded information with tile number tilenumber in the picture header.  Note that tile numbers begin at zero.  Zero is returned upon failure to write this pointer.  FdpicEncodeScanline uses a scanline RGBA buffer beginning at ptr to encode the next scanline of the named picture output channel.

FdpicPostEncodeScanline ends the encoding of this tile. 

LIBRARY

libfdpicio.a

SEE ALSO

libfdpicio (3H)− overview of the fast disk picio library
FdPicClose (3H), FdPicCreat (3H), FdPicLabel (3H), FdPicRead (3H), FdPicDecode (3H)

BUGS

Abuse of the lseek pointer into the picture being encoded will trash the encoding.  Although concurrent encoding is supported, concurrent encoding of tiles in the same picture is not. 

DIAGNOSTICS

FdpicPreEncodeScanline returns 0 if the tilenumber is bad or internal buffer space cannot be allocated.  FdpicEncodeScanline returns 0 if FdpicPreEncodeScanline has not been called or upon any disk write error (i.e., when there is no more space).  FdpicPostEncodeScanline returns 0 if the number of calls to picEncodeScanline is not equal to the height of the tile.  This indicates a malformed tile. 

Release β  —  Last change: 8/3/88