NAME

       Imager::Preprocess - simple preprocessor for handling multiple sample sizes

SYNOPSIS

         /* 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

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.

       Imager's "Makefile.PL" currently scans the MANIFEST for .im files and adds Makefile files
       to convert these to .c files.

       The beginning of a sample-independent section of code is preceded by:

         #code expression

       where expression should return true if processing should be done at 8-bits/sample.

       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 IM_SUFFIX() to produce different function names.

       The end of a sample-independent section of code is terminated by:

         #/code

       #code sections cannot be nested.

       #/code without a starting #code is an error.

       You can also define extra sample-size dependent macros with "#!define":

           "#define" common-name eight-bit-name floating-point-name

       The following types and values are defined in a #code section:

       •   IM_GPIX("im", "x", "y", &col)

       •   IM_GLIN("im", "l", "r", "y", "colors")

       •   IM_PPIX("im", "x", "y", &col)

       •   IM_PLIN("im", "x", "y", "colors")

       •   IM_GSAMP("im", "l", "r", "y", "samples", "chans", "chan_count")

           These correspond to the appropriate image function, eg. IM_GPIX() becomes i_gpix() or
           i_gpixf() as appropriate.

       •   IM_ADAPT_COLORS("dest_channels", "src_channels", "colors", "count")

           Call i_adapt_colors() or i_adapt_fcolors().

       •   IM_FILL_COMBINE("fill") - retrieve the combine function from a fill object.

       •   IM_FILL_FILLER("fill") - retrieve the fill_with_* function from a fill object.

       •   IM_ABS(sample) - calculate the absolute value of an IM_WORK_T value.

       •   IM_SAMPLE_MAX - maximum value for a sample

       •   IM_SAMPLE_MAX2 - maximum value for a sample, squared

       •   IM_SAMPLE_T - type of a sample (i_sample_t or i_fsample_t)

       •   IM_COLOR - color type, either i_color or i_fcolor.

       •   IM_WORK_T - working sample type, either int or double.

       •   IM_Sf - format string for the sample type, "%d" or "%f".

       •   IM_Wf - format string for the work type, "%d" or "%f".

       •   IM_SUFFIX(identifier) - adds _8 or _double onto the end of identifier.

       •   IM_EIGHT_BIT - this is a macro defined only in 8-bit/sample code.

       Other types, functions and values may be added in the future.

AUTHOR

       Tony Cook <tonyc@cpan.org>