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.\" ========================================================================
.\"
.IX Title "Imager::Preprocess 3pm"
.TH Imager::Preprocess 3pm "2020-11-08" "perl v5.32.0" "User Contributed Perl Documentation"
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.nh
.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 \fI\s-1MANIFEST\s0\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 \s-1\fBIM_SUFFIX\s0()\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
The following types and values are defined in a #code section:
.IP "\(bu" 4
\&\s-1IM_GPIX\s0(\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
\&\s-1IM_GLIN\s0(\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
\&\s-1IM_PPIX\s0(\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
\&\s-1IM_PLIN\s0(\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
\&\s-1IM_GSAMP\s0(\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. \s-1\fBIM_GPIX\s0()\fR
becomes \fBi_gpix()\fR or \fBi_gpixf()\fR as appropriate.
.IP "\(bu" 4
\&\s-1IM_ADAPT_COLORS\s0(\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
\&\s-1IM_FILL_COMBINE\s0(\f(CW\*(C`fill\*(C'\fR) \- retrieve the combine function from a fill
object.
.IP "\(bu" 4
\&\s-1IM_FILL_FILLER\s0(\f(CW\*(C`fill\*(C'\fR) \- retrieve the fill_with_* function from a fill
object.
.IP "\(bu" 4
\&\s-1IM_SAMPLE_MAX\s0 \- maximum value for a sample
.IP "\(bu" 4
\&\s-1IM_SAMPLE_MAX2\s0 \- maximum value for a sample, squared
.IP "\(bu" 4
\&\s-1IM_SAMPLE_T\s0 \- type of a sample (i_sample_t or i_fsample_t)
.IP "\(bu" 4
\&\s-1IM_COLOR\s0 \- color type, either i_color or i_fcolor.
.IP "\(bu" 4
\&\s-1IM_WORK_T\s0 \- 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
\&\s-1IM_SUFFIX\s0(identifier) \- adds _8 or _double onto the end of identifier.
.IP "\(bu" 4
\&\s-1IM_EIGHT_BIT\s0 \- 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>