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.\"
.IX Title "Imager::Preprocess 3pm"
.TH Imager::Preprocess 3pm 2024-04-13 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
Imager::Preprocess \- simple preprocessor for handling multiple sample sizes
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 4
\&  /* in the source: */
\&  #code condition true to work with 8\-bit samples
\&  ... code using preprocessor types/values ...
\&  #/code
\&
\&  # process and make #line directives
\&  perl \-MImager::Preprocess \-epreprocess foo.im foo.c
\&
\&  # process and no #line directives
\&  perl \-MImager::Preprocess \-epreprocess \-l foo.im foo.c
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This is a simple preprocessor that aims to reduce duplication of
source code when implementing an algorithm both for 8\-bit samples and
double samples in Imager.
.PP
Imager's \f(CW\*(C`Makefile.PL\*(C'\fR currently scans the \fIMANIFEST\fR for \fI.im\fR
files and adds Makefile files to convert these to \fI.c\fR files.
.PP
The beginning of a sample-independent section of code is preceded by:
.PP
.Vb 1
\&  #code expression
.Ve
.PP
where \fIexpression\fR should return true if processing should be done at
8\-bits/sample.
.PP
You can also use a #code block around a function definition to produce
8\-bit and double sample versions of a function.  In this case #code
has no expression and you will need to use \fBIM_SUFFIX()\fR to produce
different function names.
.PP
The end of a sample-independent section of code is terminated by:
.PP
.Vb 1
\&  #/code
.Ve
.PP
#code sections cannot be nested.
.PP
#/code without a starting #code is an error.
.PP
You can also define extra sample-size dependent macros with \f(CW\*(C`#!define\*(C'\fR:
.Sp
.RS 4
\&\f(CW\*(C`#define\*(C'\fR \fIcommon-name\fR \fIeight-bit-name\fR \fIfloating-point-name\fR
.RE
.PP
The following types and values are defined in a #code section:
.IP \(bu 4
IM_GPIX(\f(CW\*(C`im\*(C'\fR, \f(CW\*(C`x\*(C'\fR, \f(CW\*(C`y\*(C'\fR, \f(CW&col\fR)
.IP \(bu 4
IM_GLIN(\f(CW\*(C`im\*(C'\fR, \f(CW\*(C`l\*(C'\fR, \f(CW\*(C`r\*(C'\fR, \f(CW\*(C`y\*(C'\fR, \f(CW\*(C`colors\*(C'\fR)
.IP \(bu 4
IM_PPIX(\f(CW\*(C`im\*(C'\fR, \f(CW\*(C`x\*(C'\fR, \f(CW\*(C`y\*(C'\fR, \f(CW&col\fR)
.IP \(bu 4
IM_PLIN(\f(CW\*(C`im\*(C'\fR, \f(CW\*(C`x\*(C'\fR, \f(CW\*(C`y\*(C'\fR, \f(CW\*(C`colors\*(C'\fR)
.IP \(bu 4
IM_GSAMP(\f(CW\*(C`im\*(C'\fR, \f(CW\*(C`l\*(C'\fR, \f(CW\*(C`r\*(C'\fR, \f(CW\*(C`y\*(C'\fR, \f(CW\*(C`samples\*(C'\fR, \f(CW\*(C`chans\*(C'\fR, \f(CW\*(C`chan_count\*(C'\fR)
.Sp
These correspond to the appropriate image function, eg. \fBIM_GPIX()\fR
becomes \fBi_gpix()\fR or \fBi_gpixf()\fR as appropriate.
.IP \(bu 4
IM_ADAPT_COLORS(\f(CW\*(C`dest_channels\*(C'\fR, \f(CW\*(C`src_channels\*(C'\fR, \f(CW\*(C`colors\*(C'\fR, \f(CW\*(C`count\*(C'\fR)
.Sp
Call \fBi_adapt_colors()\fR or \fBi_adapt_fcolors()\fR.
.IP \(bu 4
IM_FILL_COMBINE(\f(CW\*(C`fill\*(C'\fR) \- retrieve the combine function from a fill
object.
.IP \(bu 4
IM_FILL_FILLER(\f(CW\*(C`fill\*(C'\fR) \- retrieve the fill_with_* function from a fill
object.
.IP \(bu 4
IM_ABS(sample) \- calculate the absolute value of an IM_WORK_T value.
.IP \(bu 4
IM_SAMPLE_MAX \- maximum value for a sample
.IP \(bu 4
IM_SAMPLE_MAX2 \- maximum value for a sample, squared
.IP \(bu 4
IM_SAMPLE_T \- type of a sample (i_sample_t or i_fsample_t)
.IP \(bu 4
IM_COLOR \- color type, either i_color or i_fcolor.
.IP \(bu 4
IM_WORK_T \- working sample type, either int or double.
.IP \(bu 4
IM_Sf \- format string for the sample type, \f(CW"%d"\fR or \f(CW"%f"\fR.
.IP \(bu 4
IM_Wf \- format string for the work type, \f(CW"%d"\fR or \f(CW"%f"\fR.
.IP \(bu 4
IM_SUFFIX(identifier) \- adds _8 or _double onto the end of identifier.
.IP \(bu 4
IM_EIGHT_BIT \- this is a macro defined only in 8\-bit/sample code.
.PP
Other types, functions and values may be added in the future.
.SH AUTHOR
.IX Header "AUTHOR"
Tony Cook <tonyc@cpan.org>