'\" te
.\" Copyright (c) 2007, Sun Microsystems, Inc.  All Rights Reserved 
.TH mlib_ImageDivAlpha 3MLIB "2 Mar 2007" "SunOS 5.11" "mediaLib Library Functions"
.SH NAME
mlib_ImageDivAlpha \- alpha channel division
.SH SYNOPSIS
.LP
.nf
cc [ \fIflag\fR... ] \fIfile\fR... \fB-lmlib\fR [ \fIlibrary\fR... ]
#include <mlib.h>

\fBmlib_status\fR \fBmlib_ImageDivAlpha\fR(\fBmlib_image *\fR\fIdst\fR, \fBconst mlib_image *\fR\fIsrc\fR,
     \fBmlib_s32\fR \fIcmask\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBmlib_ImageDivAlpha()\fR function divides color channels by the alpha channel on a pixel-by-pixel basis.
.sp
.LP
For the \fBMLIB_BYTE\fR image, it uses the following equation:
.sp
.in +2
.nf
dst[x][y][c] = src[x][y][c] / (src[x][y][a] * 2**(-8))
.fi
.in -2

.sp
.LP
For the \fBMLIB_SHORT\fR image, it uses the following equation:
.sp
.in +2
.nf
dst[x][y][c] = src[x][y][c] / (src[x][y][a] * 2**(-15))
.fi
.in -2

.sp
.LP
For the \fBMLIB_USHORT\fR image, it uses the following equation:
.sp
.in +2
.nf
dst[x][y][c] = src[x][y][c] / (src[x][y][a] * 2**(-16))
.fi
.in -2

.sp
.LP
For the \fBMLIB_INT\fR image, it uses the following equation:
.sp
.in +2
.nf
dst[x][y][c] = src[x][y][c] / (src[x][y][a] * 2**(-31))
.fi
.in -2

.sp
.LP
where \fBc\fR and \fBa\fR are the indices for the color channels and the alpha channel, respectively, so \fBc != a\fR.
.sp
.LP
In the case of src[x][y][a] = 0,
.sp
.in +2
.nf
dst[x][y][c] = 0              if src[x][y][c] = 0
dst[x][y][c] = DATA_TYPE_MAX  if src[x][y][c] > 0
dst[x][y][c] = DATA_TYPE_MIN  if src[x][y][c] < 0
.fi
.in -2

.sp
.LP
where \fBDATA_TYPE\fR is \fBMLIB_U8\fR, \fBMLIB_S16\fR, \fBMLIB_U16\fR, or \fBMLIB_S32\fR for an image of type \fBMLIB_BYTE\fR, \fBMLIB_SHORT\fR, \fBMLIB_USHORT\fR, or \fBMLIB_INT\fR, respectively.
.SH PARAMETERS
.sp
.LP
The function takes the following arguments:
.sp
.ne 2
.mk
.na
\fB\fIdst\fR\fR
.ad
.RS 9n
.rt  
Pointer to destination image.
.RE

.sp
.ne 2
.mk
.na
\fB\fIsrc\fR\fR
.ad
.RS 9n
.rt  
Pointer to source image.
.RE

.sp
.ne 2
.mk
.na
\fB\fIcmask\fR\fR
.ad
.RS 9n
.rt  
Channel mask to indicate the alpha channel. Each bit of the mask represents a channel in the image. The channel corresponding to the 1 bit of \fBcmask\fR is the alpha channel.
.RE

.SH RETURN VALUES
.sp
.LP
The function returns \fBMLIB_SUCCESS\fR if successful. Otherwise it returns \fBMLIB_FAILURE\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBmlib_ImageDivAlpha_Inp\fR(3MLIB), \fBmlib_ImageDivAlpha_Fp\fR(3MLIB), \fBmlib_ImageDivAlpha_Fp_Inp\fR(3MLIB), \fBattributes\fR(5)