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Imager::Preprocess

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 AT cpan DOT org>

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