Imager::Preprocess(3) 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.

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_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 <[email protected]>

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