Imager...rocess(3pm)

💅 NAME 💅

Imager::Preprocess — it's a lil preprocessor bestie, and its whole job is handling multiple sample sizes so you don't have to write the same algorithm twice 😭✨

(This is from the User Contributed Perl Documentation, page vibes courtesy of Imager...rocess(3pm).)

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🌸 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

That's the whole ritual, no cap 💫

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🦋 DESCRIPTION 🦋

Okay so listen 👂 — this is a simple preprocessor, and its entire main character purpose is reducing duplication of source code when you're implementing an algorithm both for 8-bit samples and double samples in Imager. Like, one source, two flavors. Slay 💅

Imager's Makefile.PL currently scans the MANIFEST for .im files and adds Makefile files to convert these to .c files. So that's happening automatically, iykyk 🎀

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. Like, don't even try it 🙈

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

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🧚 Defining extra macros

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

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

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✨ The types and values ✨

The following types and values are defined in a #code section — memorize these, they're iconic 👑

• 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. Cute, right? 🫶
• 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. So stay tuned bestie 🌈

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👑 AUTHOR 👑

Tony Cook <tonyc@cpan.org> — thank you for your service, king 🫡💖

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Okay that's the whole page!! Brought to you by perl v5.42.3 dated 2026-08-19, and yes that's the vibe, that's the version, mwah 💋✨