g2cpng.c File Reference

These functions read/write PNG stream to/from memory. More...

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <png.h>

Go to the source code of this file.

Typedefs
typedef int	g2int
	Integer type.
typedef struct png_stream	png_stream
	location to write PNG stream

Functions
int	dec_png (unsigned char *pngbuf, g2int *width, g2int *height, char *cout)
	Decode some PNG compressed data.
int	enc_png (char *data, g2int *width, g2int *height, g2int *nbits, char *pngbuf)
	create png_structs to write png stream into memory.
static void	user_flush_data (png_structp png_ptr)
	Dummy Custom flush function.
static void	user_read_data (png_structp png_ptr, png_bytep data, png_uint_32 length)
	Custom read function used so that libpng will read a PNG stream from memory instead of a file on disk.
static void	user_write_data (png_structp png_ptr, png_bytep data, png_uint_32 length)
	Custom write function used to that libpng will write to memory location instead of a file on disk.

Detailed Description

These functions read/write PNG stream to/from memory.

Author

Ed Hartnett

Date

3/5/24

Definition in file g2cpng.c.

Typedef Documentation

g2int

typedef int g2int

Integer type.

Definition at line 12 of file g2cpng.c.

png_stream

typedef struct png_stream png_stream

location to write PNG stream

Definition at line 21 of file g2cpng.c.

Function Documentation

dec_png()

int dec_png	(	unsigned char *	pngbuf,
		g2int *	width,
		g2int *	height,
		char *	cout
	)

Decode some PNG compressed data.

Parameters

pngbuf	Pointer to the PNG buffer to be uncompressed.
width	Pointer to the width.
height	Pointer to the height.
cout	Pointer that gets the unpacked data.

Returns

• 0 Success
• -1 Error initializing PNG structs.
• -2 Error initializing PNG info struct.
• -3 Error initializing PNG error callbacks, or stream not valid PNG.

Author

Stephen Gilbert

Definition at line 188 of file g2cpng.c.

References user_read_data().

Referenced by pngunpack().

enc_png()

int enc_png	(	char *	data,
		g2int *	width,
		g2int *	height,
		g2int *	nbits,
		char *	pngbuf
	)

create png_structs to write png stream into memory.

Parameters

data	data.
width	width.
height	height.
nbits	number of bits.
pngbuf	PNG buffer.

Returns

pnglen the length of png stream

Author

Stephen Gilbert

Definition at line 74 of file g2cpng.c.

References user_flush_data(), and user_write_data().

Referenced by pngpack().

user_flush_data()

static void user_flush_data ( png_structp  png_ptr )

static

Dummy Custom flush function.

Parameters

png_ptr

Pointer to PNG struct.

Author

Stephen Gilbert

Definition at line 57 of file g2cpng.c.

Referenced by enc_png().

user_read_data()

static void user_read_data ( png_structp  png_ptr, png_bytep  data, png_uint_32  length  )

static

Custom read function used so that libpng will read a PNG stream from memory instead of a file on disk.

Parameters

png_ptr	Pointer to PNG.
data	Pointer to data.
length	Length.

Author

Stephen Gilbert

Definition at line 158 of file g2cpng.c.

Referenced by dec_png().

user_write_data()

static void user_write_data ( png_structp  png_ptr, png_bytep  data, png_uint_32  length  )

static

Custom write function used to that libpng will write to memory location instead of a file on disk.

Parameters

png_ptr	pointer
data	data
length	length

Author

Stephen Gilbert

Definition at line 35 of file g2cpng.c.

Referenced by enc_png().