PNG

PNG image reading and writing support. More...

Collaboration diagram for PNG:

Data Structures
struct	gdPngWriteOptions
	Options for writing PNG data. More...
struct	gdPngInfo
	Basic information read from a PNG stream. More...

Macros
#define	GD_PNG_FILTER_AUTO   0U
#define	GD_PNG_FILTER_NONE   (1U << 0)
#define	GD_PNG_FILTER_SUB   (1U << 1)
#define	GD_PNG_FILTER_UP   (1U << 2)
#define	GD_PNG_FILTER_AVERAGE   (1U << 3)
#define	GD_PNG_FILTER_PAETH   (1U << 4)
#define	GD_PNG_FILTER_ALL

Enumerations
enum	{   GD_PNG_COMPRESSION_STRATEGY_DEFAULT = 0 , GD_PNG_COMPRESSION_STRATEGY_FILTERED , GD_PNG_COMPRESSION_STRATEGY_HUFFMAN_ONLY , GD_PNG_COMPRESSION_STRATEGY_RLE ,   GD_PNG_COMPRESSION_STRATEGY_FIXED }
	PNG compression strategy values for gdPngWriteOptions. More...

Functions
gdImagePtr	gdImageCreateFromPng (FILE *fd)
	Create an image from a PNG stdio file.
gdImagePtr	gdImageCreateFromPngCtx (gdIOCtxPtr in)
	Create an image from PNG data read through a gdIOCtx.
gdImagePtr	gdImageCreateFromPngPtr (int size, void *data)
	Create an image from a PNG memory buffer.
void	gdImagePng (gdImagePtr im, FILE *out)
	Write an image as PNG data to a stdio file.
void	gdImagePngCtx (gdImagePtr im, gdIOCtxPtr out)
	Write an image as PNG data to a gdIOCtx.
void	gdImagePngEx (gdImagePtr im, FILE *out, int level)
	Write an image as PNG data to a stdio file with a compression level.
void	gdImagePngCtxEx (gdImagePtr im, gdIOCtxPtr out, int level)
	Write an image as PNG data to a gdIOCtx with a compression level.
void *	gdImagePngPtr (gdImagePtr im, int *size)
	Write an image as PNG data to a newly allocated memory buffer.
void *	gdImagePngPtrEx (gdImagePtr im, int *size, int level)
	Write an image as PNG data to a memory buffer with a compression level.
void	gdPngWriteOptionsInit (gdPngWriteOptions *options)
	Initialize PNG write options with default values.
void	gdPngInfoInit (gdPngInfo *info)
	Initialize a gdPngInfo structure with default values.
int	gdImagePngWithOptions (gdImagePtr im, FILE *out, const gdPngWriteOptions *options)
	Write an image as PNG data to a stdio file using write options.
int	gdImagePngCtxWithOptions (gdImagePtr im, gdIOCtxPtr out, const gdPngWriteOptions *options)
	Write an image as PNG data to a gdIOCtx using write options.
void *	gdImagePngPtrWithOptions (gdImagePtr im, int *size, const gdPngWriteOptions *options)
	Write an image as PNG data to a memory buffer using write options.
int	gdPngGetInfo (FILE *in, gdPngInfo *info)
	Read PNG header information from a stdio file.
int	gdPngGetInfoCtx (gdIOCtxPtr in, gdPngInfo *info)
	Read PNG header information from a gdIOCtx.
int	gdPngGetInfoPtr (int size, const void *data, gdPngInfo *info)
	Read PNG header information from a memory buffer.
const char *	gdPngGetVersionString (void)
	Return a string describing the linked libpng version.

Detailed Description

PNG image reading and writing support.

PNG support preserves palette images as palette-based gd images and reads truecolor PNG data as truecolor gd images. PNG output is palette-aware, supports alpha, metadata, compression settings, and libpng filter options.

gdImagePtr im;
int black, white;
FILE *out;
 
im = gdImageCreate(100, 100);
if (im == NULL) {
  fprintf(stderr, "Unable to create image\n");
  exit(1);
}
 
white = gdImageColorAllocate(im, 255, 255, 255);
black = gdImageColorAllocate(im, 0, 0, 0);
gdImageRectangle(im, 0, 0, 99, 99, black);
 
out = fopen("rect.png", "wb");
if (out == NULL) {
   fprintf(stderr, "Unable to open output file\n");
   gdImageDestroy(im);
   exit(1);
}
 
gdImagePngEx(im, out, 9);
fclose(out);
gdImageDestroy(im);

Macro Definition Documentation

GD_PNG_FILTER_ALL

#define GD_PNG_FILTER_ALL

Value:

    (GD_PNG_FILTER_NONE | GD_PNG_FILTER_SUB | GD_PNG_FILTER_UP | GD_PNG_FILTER_AVERAGE |           \
     GD_PNG_FILTER_PAETH)

Enable all PNG row filters.

GD_PNG_FILTER_AUTO

#define GD_PNG_FILTER_AUTO   0U

Let libpng choose PNG row filters automatically.

GD_PNG_FILTER_AVERAGE

#define GD_PNG_FILTER_AVERAGE   (1U << 3)

Enable the PNG "Average" row filter.

GD_PNG_FILTER_NONE

#define GD_PNG_FILTER_NONE   (1U << 0)

Enable the PNG "None" row filter.

GD_PNG_FILTER_PAETH

#define GD_PNG_FILTER_PAETH   (1U << 4)

Enable the PNG "Paeth" row filter.

GD_PNG_FILTER_SUB

#define GD_PNG_FILTER_SUB   (1U << 1)

Enable the PNG "Sub" row filter.

GD_PNG_FILTER_UP

#define GD_PNG_FILTER_UP   (1U << 2)

Enable the PNG "Up" row filter.

Enumeration Type Documentation

anonymous enum

anonymous enum

PNG compression strategy values for gdPngWriteOptions.

Enumerator
GD_PNG_COMPRESSION_STRATEGY_DEFAULT	Use zlib's default strategy.
GD_PNG_COMPRESSION_STRATEGY_FILTERED	Prefer zlib's filtered-data strategy.
GD_PNG_COMPRESSION_STRATEGY_HUFFMAN_ONLY	Use Huffman coding only.
GD_PNG_COMPRESSION_STRATEGY_RLE	Use zlib's run-length encoding strategy.
GD_PNG_COMPRESSION_STRATEGY_FIXED	Use zlib's fixed Huffman codes strategy.

Function Documentation

gdImageCreateFromPng()

gdImagePtr gdImageCreateFromPng

(

FILE *

fd

)

Create an image from a PNG stdio file.

Parameters

fd	Pointer to the input FILE stream.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromPngCtx()

gdImagePtr gdImageCreateFromPngCtx

(

gdIOCtxPtr

in

)

Create an image from PNG data read through a gdIOCtx.

Parameters

in	Pointer to the gdIOCtx input context.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromPngPtr()

gdImagePtr gdImageCreateFromPngPtr	(	int	size,
		void *	data
	)

Create an image from a PNG memory buffer.

Parameters

size	Size of the PNG memory buffer in bytes.
data	Pointer to the PNG memory buffer.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImagePng()

void gdImagePng	(	gdImagePtr	im,
		FILE *	out
	)

Write an image as PNG data to a stdio file.

Parameters

im	The image to write.
out	The stdio file to write the PNG data to.

gdImagePngCtx()

void gdImagePngCtx	(	gdImagePtr	im,
		gdIOCtxPtr	out
	)

Write an image as PNG data to a gdIOCtx.

Parameters

im	The image to write.
out	The gdIOCtx to write the PNG data to.

gdImagePngCtxEx()

void gdImagePngCtxEx	(	gdImagePtr	im,
		gdIOCtxPtr	out,
		int	level
	)

Write an image as PNG data to a gdIOCtx with a compression level.

Parameters

im	The image to write.
out	The gdIOCtx to write the PNG data to.
level	Compression level: 0 for no compression, 1-9 for zlib levels, or -1 for the default.

gdImagePngCtxWithOptions()

int gdImagePngCtxWithOptions	(	gdImagePtr	im,
		gdIOCtxPtr	out,
		const gdPngWriteOptions *	options
	)

Write an image as PNG data to a gdIOCtx using write options.

Parameters

im	The image to write.
out	The gdIOCtx to write the PNG data to.
options	Pointer to a gdPngWriteOptions structure, or NULL for defaults.

Returns

Returns 0 on success, or 1 on failure.

gdImagePngEx()

void gdImagePngEx	(	gdImagePtr	im,
		FILE *	out,
		int	level
	)

Write an image as PNG data to a stdio file with a compression level.

Parameters

im	The image to write.
out	The stdio file to write the PNG data to.
level	Compression level: 0 for no compression, 1-9 for zlib levels, or -1 for the default.

gdImagePngPtr()

void * gdImagePngPtr	(	gdImagePtr	im,
		int *	size
	)

Write an image as PNG data to a newly allocated memory buffer.

Parameters

im	The image to write.
size	Pointer to an integer that receives the returned buffer size.

Returns

A pointer to the newly allocated PNG data, or NULL on failure.

gdImagePngPtrEx()

void * gdImagePngPtrEx	(	gdImagePtr	im,
		int *	size,
		int	level
	)

Write an image as PNG data to a memory buffer with a compression level.

Parameters

im	The image to write.
size	Pointer to an integer that receives the returned buffer size.
level	Compression level: 0 for no compression, 1-9 for zlib levels, or -1 for the default.

Returns

A pointer to the newly allocated PNG data, or NULL on failure.

gdImagePngPtrWithOptions()

void * gdImagePngPtrWithOptions	(	gdImagePtr	im,
		int *	size,
		const gdPngWriteOptions *	options
	)

Write an image as PNG data to a memory buffer using write options.

Parameters

im	The image to write.
size	Pointer to an integer that receives the returned buffer size.
options	Pointer to a gdPngWriteOptions structure, or NULL for defaults.

Returns

A pointer to the newly allocated PNG data, or NULL on failure.

gdImagePngWithOptions()

int gdImagePngWithOptions	(	gdImagePtr	im,
		FILE *	out,
		const gdPngWriteOptions *	options
	)

Write an image as PNG data to a stdio file using write options.

Parameters

im	The image to write.
out	The stdio file to write the PNG data to.
options	Pointer to a gdPngWriteOptions structure, or NULL for defaults.

Returns

Returns 0 on success, or 1 on failure.

gdPngGetInfo()

int gdPngGetInfo	(	FILE *	in,
		gdPngInfo *	info
	)

Read PNG header information from a stdio file.

Parameters

in	Pointer to the input FILE stream.
info	Pointer to the gdPngInfo structure to populate.

Returns

Returns 0 on success, or 1 on failure.

gdPngGetInfoCtx()

int gdPngGetInfoCtx	(	gdIOCtxPtr	in,
		gdPngInfo *	info
	)

Read PNG header information from a gdIOCtx.

Parameters

in	Pointer to the gdIOCtx input context.
info	Pointer to the gdPngInfo structure to populate.

Returns

Returns 0 on success, or 1 on failure.

gdPngGetInfoPtr()

int gdPngGetInfoPtr	(	int	size,
		const void *	data,
		gdPngInfo *	info
	)

Read PNG header information from a memory buffer.

Parameters

size	Size of the PNG memory buffer in bytes.
data	Pointer to the PNG memory buffer.
info	Pointer to the gdPngInfo structure to populate.

Returns

Returns 0 on success, or 1 on failure.

gdPngGetVersionString()

const char * gdPngGetVersionString

(

void

)

Return a string describing the linked libpng version.

Returns

Returns the linked libpng version string.

gdPngInfoInit()

void gdPngInfoInit

(

gdPngInfo *

info

)

Initialize a gdPngInfo structure with default values.

Parameters

info	Pointer to the gdPngInfo structure to initialize.

gdPngWriteOptionsInit()

void gdPngWriteOptionsInit

(

gdPngWriteOptions *

options

)

Initialize PNG write options with default values.

Parameters

options

Pointer to the gdPngWriteOptions structure to initialize.