pngpack.c File Reference

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

#include <stdlib.h>
#include <math.h>
#include "grib2.h"

Go to the source code of this file.

Functions
int	enc_png (char *, g2int, g2int, g2int, char *)
	Encode PNG. More...
void	pngpack (g2float *fld, g2int width, g2int height, g2int *idrstmpl, unsigned char *cpack, g2int *lcpack)
	This subroutine packs up a data field 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

enc_png()

int enc_png	(	char *	data,
		g2int	width,
		g2int	height,
		g2int	nbits,
		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 81 of file enc_png.c.

References user_flush_data(), and user_write_data().

Referenced by pngpack().

pngpack()

void pngpack	(	g2float *	fld,
		g2int	width,
		g2int	height,
		g2int *	idrstmpl,
		unsigned char *	cpack,
		g2int *	lcpack
	)

This subroutine packs up a 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	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

Definition at line 38 of file pngpack.c.

References enc_png(), int_power(), mkieee(), and sbits().

Referenced by g2_addfield().