Function to pack data with PNG compression. More...

#include <stdlib.h>
#include <math.h>
#include "grib2_int.h"

Functions
int	g2c_pngpackd (double fld, size_t width, size_t height, int idrstmpl, unsigned char cpack, int lcpack)
	This subroutine packs up a double data field into PNG image format. More...

int	g2c_pngpackf (float fld, size_t width, size_t height, int idrstmpl, unsigned char cpack, int lcpack)
	This subroutine packs up a float data field into PNG image format. More...

void	pngpack (float fld, g2int width, g2int height, g2int idrstmpl, unsigned char cpack, g2int lcpack)
	This subroutine packs up a float data field into PNG image format. More...

static int	pngpack_int (void fld, int fld_is_double, g2int width, g2int height, g2int idrstmpl, unsigned char cpack, g2int lcpack, int verbose)
	This internal function packs up float or double data into PNG image format. More...

Detailed Description

Function to pack data with PNG compression.

Author: Stephen Gilbert

Date: 2003-08-27

Definition in file pngpack.c.

Function Documentation

◆ g2c_pngpackd()

int g2c_pngpackd	(	double *	fld,
		size_t	width,
		size_t	height,
		int *	idrstmpl,
		unsigned char *	cpack,
		int *	lcpack
	)

This subroutine packs up a double data field into PNG image format.

After the data field is scaled, and the reference value is subtracted out, it is treated as a grayscale image and passed to a PNG encoder. It also fills in GRIB2 Data Representation Template 5.41 or 5.40010 with the appropriate values.

Parameters

fld	Pointer to array of double that contains the data values to pack.
width	Number of points in the x direction.
height	Number of points in the y direction.
idrstmpl	Contains the array of values for Data Representation Template 5.41 or 5.40010. 0 Reference value - ignored on input, set by pngpack routine. 1 Binary Scale Factor - used on input. 2 Decimal Scale Factor - used on input. 3 number of bits for each grayscale pixel value - ignored on input. 4 Original field type - currently ignored on input, set = 0 on output. Data values assumed to be reals.
cpack	The packed data field.
lcpack	length of packed field cpack.

Returns

G2C_NOERROR No error.
G2C_EPNG Error encoding/decoding PNG data.

Author: Ed Hartnett

Date: Aug 8, 2022

Definition at line 336 of file pngpack.c.

References G2C_PNG_DRS_TEMPLATE_LEN, and pngpack_int().

◆ g2c_pngpackf()

int g2c_pngpackf	(	float *	fld,
		size_t	width,
		size_t	height,
		int *	idrstmpl,
		unsigned char *	cpack,
		int *	lcpack
	)

This subroutine packs up a float data field into PNG image format.

After the data field is scaled, and the reference value is subtracted out, it is treated as a grayscale image and passed to a PNG encoder. It also fills in GRIB2 Data Representation Template 5.41 or 5.40010 with the appropriate values.

Parameters

fld	Pointer to array of float that contains the data values to pack.
width	Number of points in the x direction.
height	Number of points in the y direction.
idrstmpl	Contains the array of values for Data Representation Template 5.41 or 5.40010. 0 Reference value - ignored on input, set by pngpack routine. 1 Binary Scale Factor - used on input. 2 Decimal Scale Factor - used on input. 3 number of bits for each grayscale pixel value - ignored on input. 4 Original field type - currently ignored on input, set = 0 on output. Data values assumed to be reals.
cpack	The packed data field.
lcpack	length of packed field cpack.

Returns

G2C_NOERROR No error.
G2C_EPNG Error encoding/decoding PNG data.

Author: Ed Hartnett

Definition at line 282 of file pngpack.c.

References G2C_PNG_DRS_TEMPLATE_LEN, and pngpack_int().

◆ pngpack()

void pngpack	(	float *	fld,
		g2int	width,
		g2int	height,
		g2int *	idrstmpl,
		unsigned char *	cpack,
		g2int *	lcpack
	)

This subroutine packs up a float data field into PNG image format.

After the data field is scaled, and the reference value is subtracted out, it is treated as a grayscale image and passed to a PNG encoder. It also fills in GRIB2 Data Representation Template 5.41 or 5.40010 with the appropriate values.

Parameters

fld	Pointer to array of float that contains the data values to pack.
width	Number of points in the x direction.
height	Number of points in the y direction.
idrstmpl	Contains the array of values for Data Representation Template 5.41 or 5.40010. 0 Reference value - ignored on input, set by pngpack routine. 1 Binary Scale Factor - used on input. 2 Decimal Scale Factor - used on input. 3 number of bits for each grayscale pixel value - ignored on input. 4 Original field type - currently ignored on input, set = 0 on output. Data values assumed to be reals.
cpack	The packed data field.
lcpack	length of packed field cpack.

Author: Stephen Gilbert

Date: 2003-08-27

Author: Ed Hartnett

Definition at line 242 of file pngpack.c.

References pngpack_int().

Referenced by g2_addfield().

◆ pngpack_int()

static int pngpack_int	(	void *	fld,
		int	fld_is_double,
		g2int	width,
		g2int	height,
		g2int *	idrstmpl,
		unsigned char *	cpack,
		g2int *	lcpack,
		int	verbose
	)

static

This internal function packs up float or double data into PNG image format.

This is called by pngpack() and pngpackd().

After the data field is scaled, and the reference value is subtracted out, it is treated as a grayscale image and passed to a PNG encoder. It also fills in GRIB2 Data Representation Template 5.41 or 5.40010 with the appropriate values.

Parameters

fld	Pointer to array of float or double that contains the data values to pack.
fld_is_double	If non-zero, then fld is double, otherwise float.
width	Number of points in the x direction. This is passed to the PNG layer as a uint32.
height	Number of points in the y direction. This is passed to the PNG layer as a uint32.
idrstmpl	Contains the array of values for Data Representation Template 5.41 or 5.40010. 0 Reference value - ignored on input, set by pngpack routine. 1 Binary Scale Factor - used on input. 2 Decimal Scale Factor - used on input. 3 number of bits for each grayscale pixel value - ignored on input. 4 Original field type - currently ignored on input, set = 0 on output. Data values assumed to be reals.
cpack	The packed data field.
lcpack	length of packed field cpack.
verbose	If non-zero, error messages will be printed in case of error. Otherwise, error codes will be return but no error messages printed. Calls to the original g2c API may cause error messages to be printed in case of error. For the new g2c_ API, no error messages will be printed - instead an error code will be returned. Call g2c_strerror() to get the error message for any error code.

Returns

G2C_NOERROR No error.
G2C_EPNG Error encoding/decoding PNG data.

Author: Ed Hartnett

Date: Aug 8, 2022

Definition at line 53 of file pngpack.c.

References ALOG2, enc_png(), G2C_EPNG, G2C_NOERROR, int_power(), LOG, mkieee(), and sbits().

Referenced by g2c_pngpackd(), g2c_pngpackf(), and pngpack().

Functions

Detailed Description

Function Documentation

◆ g2c_pngpackd()

◆ g2c_pngpackf()

◆ pngpack()

◆ pngpack_int()