iffliction

A small C library that detects, inspects, decodes, and converts the classic Amiga image and icon formats into modern RGBA buffers, PNG files, and (optionally) SDL_Surface objects.

Supported formats

Format	Description
IFF ILBM / PBM	Classic Amiga IFF images: 1–8 bitplanes, 24-bit deep ILBM, HAM6 / HAM8, EHB, ByteRun1 compression, optional mask plane
Classic / MagicWB	The original 8-color .info icon (depth-1..4); depth-3 with the standard MagicWB palette is the MagicWB profile
NewIcons	Image data hidden inside ToolTypes IM1= / IM2= lines (Dirk Stoecker's spec)
GlowIcons	OS 3.5+ truecolor icons; an IFF FORM ICON block appended after the classic .info structure

Public API

The header is iffliction.h. Every function in the public API is prefixed with iffliction_*; internal helpers are prefixed _iffliction_* and have file-scope linkage.

TEST — does this file match a given format?

int iffliction_is_iff_image      (const char *file_path);
int iffliction_is_magicwb_icon   (const char *file_path);
int iffliction_is_new_icon       (const char *file_path);
int iffliction_is_glow_icon      (const char *file_path);
iffliction_type_t iffliction_detect_type(const char *file_path);
const char *iffliction_type_name (iffliction_type_t t);

Returns 1 if the file matches that specific format, 0 if it does not, -1 on I/O error.

iffliction_detect_type() returns the most specific match (GlowIcons > NewIcons > MagicWB > generic classic icon > IFF image).

INFORMATION — metadata without decoding pixels

int iffliction_get_iff_image_information   (const char *path, iffliction_info_t *out);
int iffliction_get_magicwb_icon_information(const char *path, iffliction_info_t *out);
int iffliction_get_new_icon_information    (const char *path, iffliction_info_t *out);
int iffliction_get_glow_icon_information   (const char *path, iffliction_info_t *out);

Fills iffliction_info_t (width, height, depth, num_colors, num_images, has_transparency, plus format-specific fields like camg, is_ham, icon_type, etc.). Returns 0 on success, -1 on error.

DECODE — RGBA pixel data

int iffliction_magicwb_icon_decode(const char *path,
                                   iffliction_image_t *out_normal,
                                   iffliction_image_t *out_selected);
int iffliction_new_icon_decode    (const char *path,
                                   iffliction_image_t *out_normal,
                                   iffliction_image_t *out_selected);
int iffliction_glow_icon_decode   (const char *path,
                                   iffliction_image_t *out_normal,
                                   iffliction_image_t *out_selected);
int iffliction_iff_decode         (const char *path,
                                   iffliction_image_t *out);
void iffliction_free_image        (iffliction_image_t *img);

Icon decoders return 1 (only normal image) or 2 (normal + selected), or -1 on error. out_selected may be NULL to skip it. Image buffers are RGBA8 of width * height * 4 bytes and are owned by the caller — release with iffliction_free_image() or plain free(img.pixels).

SAVE_AS_PNG

int iffliction_magicwb_icon_save_as_png(const char *path, const char *out_prefix);
int iffliction_new_icon_save_as_png    (const char *path, const char *out_prefix);
int iffliction_glow_icon_save_as_png   (const char *path, const char *out_prefix);
int iffliction_iff_save_as_png         (const char *path, const char *out_path);

int iffliction_save_rgba_as_png(const char *out_path, const uint8_t *rgba,
                                int w, int h);

Icon formats produce <prefix>_1.png for the normal image, and <prefix>_2.png for the selected one if present. Pass out_prefix = NULL to derive a prefix from the source path (strips a trailing .info). IFF images produce a single PNG; pass out_path = NULL to replace the source extension with .png. Returns the number of PNG files written or -1 on error.

CONVERT_TO_SDL_SURFACE (optional)

Built only if compiled with -DIFFLICTION_WITH_SDL.

SDL_Surface *iffliction_magicwb_icon_convert_to_sdl_surface(const char *path);
SDL_Surface *iffliction_new_icon_convert_to_sdl_surface    (const char *path);
SDL_Surface *iffliction_glow_icon_convert_to_sdl_surface   (const char *path);
SDL_Surface *iffliction_iff_convert_to_sdl_surface         (const char *path);

SDL_Surface *iffliction_rgba_to_sdl_surface(const uint8_t *rgba, int w, int h);

Returns the normal image (only) as a fresh SDL_Surface in SDL_PIXELFORMAT_RGBA32. The caller releases it with SDL_FreeSurface(). For both the normal and selected images of an icon, use the *_decode function with iffliction_rgba_to_sdl_surface().

Error reporting

const char *iffliction_last_error(void);

Returns a human-readable message describing the most recent failure, or NULL if no error has occurred since the last successful call. Process-wide, single-threaded.

Building

make

Produces:

Artifact	Built with SDL?	Notes
libiffliction.a	no	Static, libpng only
libiffliction-sdl.a	yes	Static, libpng + SDL2
libiffliction.so	no	Shared, libpng only
libiffliction-sdl.so	yes	Shared, libpng + SDL2
example	yes	Demo program

Dependencies: libpng (always) and SDL2 (only for the SDL build).

Linking

cc your.c libiffliction.a -lpng                 # no SDL
cc your.c libiffliction-sdl.a -lpng -lSDL2      # with SDL

When using the shared libraries, also pass -DIFFLICTION_WITH_SDL at compile time if you intend to call any of the SDL helpers, so the SDL prototypes get pulled in from the header.

Example

#include "iffliction.h"
#include <stdio.h>

int main(void) {
    const char *path = "MyIcon.info";

    if (iffliction_is_glow_icon(path) == 1) {
        iffliction_info_t info;
        iffliction_get_glow_icon_information(path, &info);
        printf("GlowIcon %dx%d, %d colors\n",
               info.width, info.height, info.num_colors);

        iffliction_glow_icon_save_as_png(path, NULL);   /* writes MyIcon_1.png + _2.png */

#ifdef IFFLICTION_WITH_SDL
        SDL_Surface *s = iffliction_glow_icon_convert_to_sdl_surface(path);
        if (s) { /* ... use s ... */ SDL_FreeSurface(s); }
#endif
    }
    return 0;
}

See example.c for a full demo program that handles all four formats.

Implementation notes

• All multi-byte fields in .info files and IFF chunks are 68k big-endian; the library reads them through dedicated helpers.
• The MagicWB profile is not explicitly flagged in the icon format — it is detected heuristically as a classic icon whose normal image has image depth 3.
• The classic MagicWB palette assumes pen 0 is the Workbench background and is emitted as fully transparent.
• GlowIcon IMAG chunks reuse the palette of the previous chunk when the has_palette flag is clear; the library carries the shared palette across IMAG decodes.
• IFF ILBM decoding supports 1..8 bitplane indexed, 24-bit deep ILBM, HAM6 / HAM8, EHB, ByteRun1, and an optional mask plane (mapped onto alpha). PBM (DPaint chunky) is not supported.
• The library performs no implicit threading. iffliction_last_error() is process-wide; do not call across threads without external locking.

Damir Sijakovic (c) 2026.