pnglite.h

/*  pnglite.h - Interface for pnglite library
	Copyright (c) 2007 Daniel Karling

	This software is provided 'as-is', without any express or implied
	warranty. In no event will the authors be held liable for any damages
	arising from the use of this software.

	Permission is granted to anyone to use this software for any purpose,
	including commercial applications, and to alter it and redistribute it
	freely, subject to the following restrictions:

	1. The origin of this software must not be misrepresented; you must not
	   claim that you wrote the original software. If you use this software
	   in a product, an acknowledgment in the product documentation would be
	   appreciated but is not required.

	2. Altered source versions must be plainly marked as such, and must not be
	   misrepresented as being the original software.

	3. This notice may not be removed or altered from any source
	   distribution.

	Daniel Karling
	daniel.karling@gmail.com
 */

/*
 * This file was modified 22-Mar-2020 by David Hovemeyer
 * to eliminate compiler warnings.
 */


#ifndef _PNGLITE_H_
#define _PNGLITE_H_

#include <string.h>

#ifdef __cplusplus
extern "C"{
#endif

/*
	Enumerations for pnglite.
	Negative numbers are error codes and 0 and up are okay responses.
*/

enum
{
	PNG_DONE			= 1,
	PNG_NO_ERROR			= 0,
	PNG_FILE_ERROR			= -1,
	PNG_HEADER_ERROR		= -2,
	PNG_IO_ERROR			= -3,
	PNG_EOF_ERROR			= -4,
	PNG_CRC_ERROR			= -5,
	PNG_MEMORY_ERROR		= -6,
	PNG_ZLIB_ERROR			= -7,
	PNG_UNKNOWN_FILTER		= -8,
	PNG_NOT_SUPPORTED		= -9,
	PNG_WRONG_ARGUMENTS		= -10
};

/*
	The five different kinds of color storage in PNG files.
*/

enum
{
	PNG_GREYSCALE			= 0,
	PNG_TRUECOLOR			= 2,
	PNG_INDEXED			= 3,
	PNG_GREYSCALE_ALPHA		= 4,
	PNG_TRUECOLOR_ALPHA		= 6
};

/*
	Typedefs for callbacks.
*/

typedef unsigned (*png_write_callback_t)(void* input, size_t size, size_t numel, void* user_pointer);
typedef unsigned (*png_read_callback_t)(void* output, size_t size, size_t numel, void* user_pointer);
typedef void (*png_free_t)(void* p);
typedef void * (*png_alloc_t)(size_t s);

typedef struct
{
	void*				zs;				/* pointer to z_stream */
	png_read_callback_t		read_fun;
	png_write_callback_t		write_fun;
	void*				user_pointer;

	unsigned char*			png_data;
	unsigned			png_datalen;

	unsigned			width;
	unsigned			height;
	unsigned char			depth;
	unsigned char			color_type;
	unsigned char			compression_method;
	unsigned char			filter_method;
	unsigned char			interlace_method;
	unsigned char			bpp;

	unsigned char*			readbuf;
	unsigned			readbuflen;
} png_t;

/*
	Function: png_init

	This function initializes pnglite. The parameters can be used to set your own memory allocation routines following these formats:

	> void* (*custom_alloc)(size_t s)
	> void (*custom_free)(void* p)
	Parameters:
		pngalloc - Pointer to custom allocation routine. If 0 is passed, malloc from libc will be used.
		pngfree - Pointer to custom free routine. If 0 is passed, free from libc will be used.

	Returns:
		Always returns PNG_NO_ERROR.
*/

int png_init(png_alloc_t pngalloc, png_free_t pngfree);

/*
	Function: png_open_file

	This function is used to open a png file with the internal file IO system. This function should be used instead of
	png_open if no custom read function is used.

	Parameters:
		png - Empty png_t struct.
		filename - Filename of the file to be opened.

	Returns:
		PNG_NO_ERROR on success, otherwise an error code.
*/

int png_open_file(png_t *png, const char* filename);

int png_open_file_read(png_t *png, const char* filename);
int png_open_file_write(png_t *png, const char* filename);

/*
	Function: png_open

	This function reads or writes a png from/to the specified callback. The callbacks should be of the format:

	> size_t (*png_write_callback_t)(void* input, size_t size, size_t numel, void* user_pointer);
	> size_t (*png_read_callback_t)(void* output, size_t size, size_t numel, void* user_pointer).

	Only one callback has to be specified. The read callback in case of PNG reading, otherwise the write callback.

	Writing:
	The callback will be called like fwrite.

	Reading:
	The callback will be called each time pnglite needs more data. The callback should read as much data as requested,
	or return 0. This should always be possible if the PNG is sane.	If the output-buffer is a null-pointer the callback
	should only skip ahead the specified number of elements. If the callback is a null-pointer the user_pointer will be
	treated as a file pointer (use png_open_file instead).

	Parameters:
		png - png_t struct
		read_fun - Callback function for reading.
		user_pointer - User pointer to be passed to read_fun.

	Returns:
		PNG_NO_ERROR on success, otherwise an error code.
*/

int png_open(png_t* png, png_read_callback_t read_fun, void* user_pointer);

int png_open_read(png_t* png, png_read_callback_t read_fun, void* user_pointer);
int png_open_write(png_t* png, png_write_callback_t write_fun, void* user_pointer);

/*
	Function: png_print_info

	This function prints some info about the opened png file to stdout.

	Parameters:
		png - png struct to get info from.
*/

void png_print_info(png_t* png);

/*
	Function: png_error_string

	This function translates an error code to a human readable string.

	Parameters:
		error - Error code.

	Returns:
		Pointer to string.
*/

char* png_error_string(int error);

/*
	Function: png_get_data

	This function decodes the opened png file and stores the result in data. data should be big enough to hold the decoded png. Required size will be:

	> width*height*(bytes per pixel)

	Parameters:
		data - Where to store result.

	Returns:
		PNG_NO_ERROR on success, otherwise an error code.
*/

int png_get_data(png_t* png, unsigned char* data);

int png_set_data(png_t* png, unsigned width, unsigned height, char depth, int color, unsigned char* data);

/*
	Function: png_close_file

	Closes an open png file pointer. Should only be used when the png has been opened with png_open_file.

	Parameters:
		png - png to close.

	Returns:
		PNG_NO_ERROR
*/

int png_close_file(png_t* png);

#ifdef __cplusplus
}
#endif
#endif