enum.h

#define PLUM_MODE_FILENAME   ((size_t) -1)
#define PLUM_MODE_BUFFER     ((size_t) -2)
#define PLUM_MODE_CALLBACK   ((size_t) -3)
#define PLUM_MAX_MEMORY_SIZE ((size_t) -4)

/* flags: not an enum (must be unsigned long) */
/* color formats */
#define PLUM_COLOR_32              0ul /* RGBA 8.8.8.8 */
#define PLUM_COLOR_64              1ul /* RGBA 16.16.16.16 */
#define PLUM_COLOR_16              2ul /* RGBA 5.5.5.1 */
#define PLUM_COLOR_32X             3ul /* RGBA 10.10.10.2 */
#define PLUM_COLOR_MASK            3ul
#define PLUM_ALPHA_INVERT          4ul
/* palettes */
#define PLUM_PALETTE_NONE          0ul
#define PLUM_PALETTE_LOAD      0x200ul
#define PLUM_PALETTE_GENERATE  0x400ul
#define PLUM_PALETTE_FORCE     0x600ul
#define PLUM_PALETTE_MASK      0x600ul
/* palette sorting */
#define PLUM_SORT_LIGHT_FIRST      0ul
#define PLUM_SORT_DARK_FIRST   0x800ul
/* other bit flags */
#define PLUM_ALPHA_REMOVE      0x100ul
#define PLUM_SORT_EXISTING    0x1000ul
#define PLUM_PALETTE_REDUCE   0x2000ul

enum plum_image_types {
  PLUM_IMAGE_NONE,
  PLUM_IMAGE_BMP,
  PLUM_IMAGE_GIF,
  PLUM_IMAGE_PNG,
  PLUM_IMAGE_APNG,
  PLUM_IMAGE_JPEG,
  PLUM_IMAGE_PNM,
  PLUM_IMAGE_QOI,
  PLUM_NUM_IMAGE_TYPES
};

enum plum_metadata_types {
  PLUM_METADATA_NONE,
  PLUM_METADATA_COLOR_DEPTH,
  PLUM_METADATA_BACKGROUND,
  PLUM_METADATA_LOOP_COUNT,
  PLUM_METADATA_FRAME_DURATION,
  PLUM_METADATA_FRAME_DISPOSAL,
  PLUM_METADATA_FRAME_AREA,
  PLUM_NUM_METADATA_TYPES
};

enum plum_frame_disposal_methods {
  PLUM_DISPOSAL_NONE,
  PLUM_DISPOSAL_BACKGROUND,
  PLUM_DISPOSAL_PREVIOUS,
  PLUM_DISPOSAL_REPLACE,
  PLUM_DISPOSAL_BACKGROUND_REPLACE,
  PLUM_DISPOSAL_PREVIOUS_REPLACE,
  PLUM_NUM_DISPOSAL_METHODS
};

enum plum_errors {
  PLUM_OK,
  PLUM_ERR_INVALID_ARGUMENTS,
  PLUM_ERR_INVALID_FILE_FORMAT,
  PLUM_ERR_INVALID_METADATA,
  PLUM_ERR_INVALID_COLOR_INDEX,
  PLUM_ERR_TOO_MANY_COLORS,
  PLUM_ERR_UNDEFINED_PALETTE,
  PLUM_ERR_IMAGE_TOO_LARGE,
  PLUM_ERR_NO_DATA,
  PLUM_ERR_NO_MULTI_FRAME,
  PLUM_ERR_FILE_INACCESSIBLE,
  PLUM_ERR_FILE_ERROR,
  PLUM_ERR_OUT_OF_MEMORY,
  PLUM_NUM_ERRORS
};