Imager::Preprocess(3p)

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>