decenc_png.c File Reference

Decode/encode a PNG stream. More...

#include "grib2_int.h"
#include <png.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

Go to the source code of this file.

Typedefs
typedef struct png_stream	png_stream
	Typedef for PNG stream.

Functions
int	dec_png (unsigned char *pngbuf, g2int *width, g2int *height, unsigned char *cout)
	Decode PNG.
int	enc_png (unsigned char *data, g2int width, g2int height, g2int nbits, unsigned char *pngbuf)
	Encode PNG.
int	g2c_dec_png (unsigned char *pngbuf, int *width, int *height, unsigned char *cout)
	Decode PNG.
int	g2c_enc_png (unsigned char *data, int width, int height, int nbits, unsigned char *pngbuf)
	Encode PNG.
void	user_flush_data (png_structp png_ptr)
	Dummy Custom flush function.
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.
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

Decode/encode a PNG stream.

Author

Alyson Stahl

Date

2024-13-08

Definition in file decenc_png.c.

Typedef Documentation

png_stream

typedef struct png_stream png_stream

Typedef for PNG stream.

Definition at line 21 of file decenc_png.c.

Function Documentation

dec_png()

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

Decode PNG.

Parameters

pngbuf	Pointer to PNG buffer.
width	Pointer to width.
height	Pointer to height.
cout	Output buffer.

Returns

0 for success, error code otherwise.

Author

Stephen Gilbert

Definition at line 127 of file decenc_png.c.

References G2C_PNG_HEIGHT_MAX, G2C_PNG_WIDTH_MAX, and user_read_data().

Referenced by g2c_dec_png(), and pngunpack_int().

enc_png()

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

Encode PNG.

Parameters

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

Returns

PNG length, or negative number for error.

Author

Stephen Gilbert

Definition at line 259 of file decenc_png.c.

References user_flush_data(), and user_write_data().

Referenced by g2c_enc_png(), and pngpack_int().

g2c_dec_png()

int g2c_dec_png	(	unsigned char *	pngbuf,
		int *	width,
		int *	height,
		unsigned char *	cout )

Decode PNG.

Parameters

pngbuf	Pointer to PNG buffer.
width	Pointer to width.
height	Pointer to height.
cout	Output buffer.

Returns

0 for success, error code otherwise.

Author

Alyson Stahl

Definition at line 100 of file decenc_png.c.

References dec_png().

g2c_enc_png()

int g2c_enc_png	(	unsigned char *	data,
		int	width,
		int	height,
		int	nbits,
		unsigned char *	pngbuf )

Encode PNG.

Parameters

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

Returns

PNG length, or negative number for error.

Author

Alyson Stahl

Definition at line 237 of file decenc_png.c.

References enc_png().

user_flush_data()

void user_flush_data

(

png_structp

png_ptr

)

Dummy Custom flush function.

Parameters

png_ptr

Pointer to PNG struct.

Author

Stephen Gilbert

Definition at line 83 of file decenc_png.c.

Referenced by enc_png().

user_read_data()

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.

Parameters

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

Author

Stephen Gilbert

Definition at line 38 of file decenc_png.c.

Referenced by dec_png().

user_write_data()

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.

Parameters

png_ptr	pointer
data	data
length	length

Author

Stephen Gilbert

Definition at line 62 of file decenc_png.c.

Referenced by enc_png().