JPEG

JPEG image reading and writing support. More...

Collaboration diagram for JPEG:

Namespaces
namespace	im
	Write an image as JPEG data to a gdIOCtx.

Data Structures
struct	gdJpegInfo
	Basic information read from a JPEG header. More...
struct	gdJpegReadOptions
	Options for reading JPEG data. More...
struct	gdJpegWriteOptions
	Options for writing JPEG data. More...

Enumerations
enum	{   GD_JPEG_COLOR_SPACE_UNKNOWN = 0 , GD_JPEG_COLOR_SPACE_GRAYSCALE = 1 , GD_JPEG_COLOR_SPACE_RGB = 2 , GD_JPEG_COLOR_SPACE_YCBCR = 3 ,   GD_JPEG_COLOR_SPACE_CMYK = 4 , GD_JPEG_COLOR_SPACE_YCCK = 5 }
	JPEG color space identifiers reported by gdJpegInfo. More...
enum	{ GD_JPEG_DENSITY_UNIT_NONE = 0 , GD_JPEG_DENSITY_UNIT_DPI = 1 , GD_JPEG_DENSITY_UNIT_DPCM = 2 }
	JPEG density units reported by gdJpegInfo. More...
enum	{ GD_JPEG_DCT_DEFAULT = 0 , GD_JPEG_DCT_SLOW = 1 , GD_JPEG_DCT_FAST = 2 , GD_JPEG_DCT_FLOAT = 3 }
	JPEG DCT method options for gdJpegReadOptions. More...

Functions
void	gdJpegInfoInit (gdJpegInfo *info)
	Initialize a gdJpegInfo structure with default values.
void	gdJpegReadOptionsInit (gdJpegReadOptions *options)
	Initialize JPEG read options with default values.
void	gdJpegWriteOptionsInit (gdJpegWriteOptions *options)
	Initialize JPEG write options with default values.
int	gdJpegGetInfo (FILE *infile, gdJpegInfo *info)
	Read JPEG header information from a stdio file.
int	gdJpegGetInfoCtx (gdIOCtxPtr infile, gdJpegInfo *info)
	Read JPEG header information from a gdIOCtx.
int	gdJpegGetInfoPtr (int size, const void *data, gdJpegInfo *info)
	Read JPEG header information from a memory buffer.
gdImagePtr	gdImageCreateFromJpeg (FILE *infile)
	Create an image from a JPEG stdio file.
gdImagePtr	gdImageCreateFromJpegEx (FILE *infile, int ignore_warning)
	Create an image from a JPEG stdio file, controlling warning handling.
gdImagePtr	gdImageCreateFromJpegCtx (gdIOCtxPtr infile)
	Create an image from JPEG data read through a gdIOCtx.
gdImagePtr	gdImageCreateFromJpegCtxEx (gdIOCtxPtr infile, int ignore_warning)
	Create an image from a JPEG gdIOCtx, controlling warning handling.
gdImagePtr	gdImageCreateFromJpegCtxWithOptions (gdIOCtxPtr infile, const gdJpegReadOptions *options)
	Create an image from a JPEG gdIOCtx and collect metadata.
gdImagePtr	gdImageCreateFromJpegPtr (int size, void *data)
	Create an image from a JPEG memory buffer.
gdImagePtr	gdImageCreateFromJpegPtrEx (int size, void *data, int ignore_warning)
	Create an image from a JPEG memory buffer, controlling warning handling.
gdImagePtr	gdImageCreateFromJpegPtrWithOptions (int size, void *data, const gdJpegReadOptions *options)
	Create an image from a JPEG memory buffer using read options.
const char *	gdJpegGetVersionString ()
	Create an image from a JPEG memory buffer and collect metadata.
void	gdImageJpeg (gdImagePtr im, FILE *out, int quality)
	Write an image as JPEG data to a stdio file.
int	gdImageJpegWithOptions (gdImagePtr im, FILE *out, const gdJpegWriteOptions *options)
	Write an image as JPEG data to a gdIOCtx with metadata.
int	gdImageJpegCtxWithOptions (gdImagePtr im, gdIOCtxPtr out, const gdJpegWriteOptions *options)
	Write an image as JPEG data to a gdIOCtx using write options.
void *	gdImageJpegPtr (gdImagePtr im, int *size, int quality)
	Write an image as JPEG data to a newly allocated memory buffer.
void *	gdImageJpegPtrWithOptions (gdImagePtr im, int *size, const gdJpegWriteOptions *options)
	Write an image as JPEG data to a memory buffer with metadata.

Detailed Description

JPEG image reading and writing support.

GD supports a range of raster codecs for loading and saving images, including JPEG, PNG, GIF, WebP, and others. Each codec is exposed as its own subgroup with format-specific options and functions.

gdImagePtr im;
int black, white;
FILE *out;
 
im = gdImageCreate(100, 100);
if (im == NULL) {
  fprintf(stderr, "Unable to create image\n");
  exit(1);
}
 
// Allocate background
white = gdImageColorAllocate(im, 255, 255, 255);
 
// Allocate drawing color
black = gdImageColorAllocate(im, 0, 0, 0);
 
// Draw rectangle
gdImageRectangle(im, 0, 0, 99, 99, black);
 
// Open output file in binary mode
out = fopen("rect.jpg", "wb");
if (out == NULL) {
   fprintf(stderr, "Unable to open output file\n");
   exit(1);
}
// Write JPEG using default quality
gdImageJpeg(im, out, -1);
// Close file
fclose(out);
// Destroy image
gdImageDestroy(im);

Enumeration Type Documentation

anonymous enum

anonymous enum

JPEG color space identifiers reported by gdJpegInfo.

Enumerator
GD_JPEG_COLOR_SPACE_UNKNOWN	Unknown or unsupported JPEG color space.
GD_JPEG_COLOR_SPACE_GRAYSCALE	Grayscale JPEG color space.
GD_JPEG_COLOR_SPACE_RGB	RGB JPEG color space.
GD_JPEG_COLOR_SPACE_YCBCR	YCbCr JPEG color space.
GD_JPEG_COLOR_SPACE_CMYK	CMYK JPEG color space.
GD_JPEG_COLOR_SPACE_YCCK	YCCK JPEG color space.

anonymous enum

anonymous enum

JPEG density units reported by gdJpegInfo.

Enumerator
GD_JPEG_DENSITY_UNIT_NONE	No density unit is specified.
GD_JPEG_DENSITY_UNIT_DPI	Density is measured in dots per inch.
GD_JPEG_DENSITY_UNIT_DPCM	Density is measured in dots per centimeter.

anonymous enum

anonymous enum

JPEG DCT method options for gdJpegReadOptions.

Enumerator
GD_JPEG_DCT_DEFAULT	Use the JPEG library default DCT method.
GD_JPEG_DCT_SLOW	Use the slow integer DCT method.
GD_JPEG_DCT_FAST	Use the fast integer DCT method.
GD_JPEG_DCT_FLOAT	Use the floating-point DCT method.

Function Documentation

gdImageCreateFromJpeg()

gdImagePtr gdImageCreateFromJpeg

(

FILE *

infile

)

Create an image from a JPEG stdio file.

Parameters

infile

Pointer to the input FILE stream.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegCtx()

gdImagePtr gdImageCreateFromJpegCtx

(

gdIOCtxPtr

infile

)

Create an image from JPEG data read through a gdIOCtx.

Parameters

infile

Pointer to the gdIOCtx input context.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegCtxEx()

gdImagePtr gdImageCreateFromJpegCtxEx	(	gdIOCtxPtr	infile,
		int	ignore_warning
	)

Create an image from a JPEG gdIOCtx, controlling warning handling.

Parameters

infile	Pointer to the gdIOCtx input context.
ignore_warning	Non-zero to suppress recoverable JPEG warnings.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegCtxWithOptions()

gdImagePtr gdImageCreateFromJpegCtxWithOptions	(	gdIOCtxPtr	infile,
		const gdJpegReadOptions *	options
	)

Create an image from a JPEG gdIOCtx and collect metadata.

Parameters

infile	Pointer to the gdIOCtx input context.
metadata	Pointer to a gdImageMetadata structure to collect metadata.

Returns

Returns a gdImagePtr on success, or NULL on failure.

Create an image from a JPEG gdIOCtx with warning control and metadata collection.

Parameters

infile	Pointer to the gdIOCtx input context.
ignore_warning	Non-zero to suppress recoverable JPEG warnings.
metadata	Pointer to a gdImageMetadata structure to collect metadata.

Returns

Returns a gdImagePtr on success, or NULL on failure.

Create an image from a JPEG gdIOCtx using read options.

Parameters

infile	Pointer to the gdIOCtx input context.
options	Pointer to a gdJpegReadOptions structure specifying read options.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegEx()

gdImagePtr gdImageCreateFromJpegEx	(	FILE *	infile,
		int	ignore_warning
	)

Create an image from a JPEG stdio file, controlling warning handling.

Parameters

infile	Pointer to the input FILE stream.
ignore_warning	Non-zero to suppress recoverable JPEG warnings.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegPtr()

gdImagePtr gdImageCreateFromJpegPtr	(	int	size,
		void *	data
	)

Create an image from a JPEG memory buffer.

Parameters

size	The size of the JPEG memory buffer.
data	Pointer to the JPEG memory buffer.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegPtrEx()

gdImagePtr gdImageCreateFromJpegPtrEx	(	int	size,
		void *	data,
		int	ignore_warning
	)

Create an image from a JPEG memory buffer, controlling warning handling.

Parameters

size	The size of the JPEG memory buffer.
data	Pointer to the JPEG memory buffer.
ignore_warning	Non-zero to suppress recoverable JPEG warnings.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageCreateFromJpegPtrWithOptions()

gdImagePtr gdImageCreateFromJpegPtrWithOptions	(	int	size,
		void *	data,
		const gdJpegReadOptions *	options
	)

Create an image from a JPEG memory buffer using read options.

Parameters

size	The size of the JPEG memory buffer.
data	Pointer to the JPEG memory buffer.
options	Pointer to a gdJpegReadOptions structure specifying read options.

Returns

Returns a gdImagePtr on success, or NULL on failure.

gdImageJpeg()

void gdImageJpeg	(	gdImagePtr	im,
		FILE *	out,
		int	quality
	)

Write an image as JPEG data to a stdio file.

100 is the highest quality (there is always a little loss with JPEG). 0 is the lowest quality. 10 is about the lowest useful setting.

Parameters

im	The image to write.
out	The stdio file to write the JPEG data to.
quality	The JPEG quality (0-100).

gdImageJpegCtxWithOptions()

int gdImageJpegCtxWithOptions	(	gdImagePtr	im,
		gdIOCtxPtr	out,
		const gdJpegWriteOptions *	options
	)

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

Parameters

im	The image to write.
out	The gdIOCtx to write the JPEG data to.
options	Pointer to a gdJpegWriteOptions struct containing the desired write options.

Returns

Returns 0 on success, or a negative value on error.

gdImageJpegPtr()

void * gdImageJpegPtr	(	gdImagePtr	im,
		int *	size,
		int	quality
	)

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

Result must be freed with gdFree(). The image is borrowed for the duration of the call.

Parameters

im	The image to write.
size	Pointer to an integer that will receive the size of the returned buffer.
quality	The JPEG quality (0-100).

Returns

A pointer to the newly allocated buffer containing the JPEG data, or NULL on failure.

gdImageJpegPtrWithOptions()

void * gdImageJpegPtrWithOptions	(	gdImagePtr	im,
		int *	size,
		const gdJpegWriteOptions *	options
	)

Write an image as JPEG data to a memory buffer with metadata.

Parameters

im	The image to write.
size	Pointer to an integer that will receive the size of the returned buffer.
quality	The JPEG quality (0-100).
metadata	Pointer to a gdImageMetadata structure containing the metadata to include in the JPEG file.

Returns

A pointer to the newly allocated buffer containing the JPEG data, or NULL on failure.

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

Parameters

im	The image to write.
size	Pointer to an integer that will receive the size of the returned buffer.
options	Pointer to a gdJpegWriteOptions struct containing the desired write options.

Returns

A pointer to the newly allocated buffer containing the JPEG data, or NULL on failure.

gdImageJpegWithOptions()

int gdImageJpegWithOptions	(	gdImagePtr	im,
		FILE *	out,
		const gdJpegWriteOptions *	options
	)

Write an image as JPEG data to a gdIOCtx with metadata.

Parameters

im	The image to write.
out	The gdIOCtx to write the JPEG data to.
quality	The JPEG quality (0-100).
metadata	Pointer to a gdImageMetadata structure containing the metadata to include in the JPEG file.

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

Parameters

im	The image to write.
out	The stdio file to write the JPEG data to.
options	Pointer to a gdJpegWriteOptions struct containing the desired write options.

Returns

Returns 0 on success, or a negative value on error.

gdJpegGetInfo()

int gdJpegGetInfo	(	FILE *	infile,
		gdJpegInfo *	info
	)

Read JPEG header information from a stdio file.

Parameters

infile	Pointer to the input FILE stream.
info	Pointer to the gdJpegInfo structure to populate with header information.

Returns

Returns 1 on success, 0 on failure.

gdJpegGetInfoCtx()

int gdJpegGetInfoCtx	(	gdIOCtxPtr	infile,
		gdJpegInfo *	info
	)

Read JPEG header information from a gdIOCtx.

Parameters

infile	Pointer to the gdIOCtx input context.
info	Pointer to the gdJpegInfo structure to populate with header information.

Returns

Returns 1 on success, 0 on failure.

gdJpegGetInfoPtr()

int gdJpegGetInfoPtr	(	int	size,
		const void *	data,
		gdJpegInfo *	info
	)

Read JPEG header information from a memory buffer.

Parameters

size	Size of the memory buffer.
data	Pointer to the memory buffer containing JPEG data.
info	Pointer to the gdJpegInfo structure to populate with header information.

Returns

Returns 1 on success, 0 on failure.

gdJpegGetVersionString()

const char * gdJpegGetVersionString

(

)

Create an image from a JPEG memory buffer and collect metadata.

Create a JPEG image from memory using read options and collect metadata.

Parameters

size	The size of the JPEG memory buffer.
data	Pointer to the JPEG memory buffer.
metadata	Pointer to a gdImageMetadata structure to collect metadata.

Returns

Returns a gdImagePtr on success, or NULL on failure.

Create an image from a JPEG memory buffer with warning control and metadata collection.

Parameters

size	The size of the JPEG memory buffer.
data	Pointer to the JPEG memory buffer.
ignore_warning	Non-zero to suppress recoverable JPEG warnings.
metadata	Pointer to a gdImageMetadata structure to collect metadata.

Returns

Returns a gdImagePtr on success, or NULL on failure.

Return a string describing the linked JPEG library version.

Returns

Returns a string describing the linked JPEG library version.

gdJpegInfoInit()

void gdJpegInfoInit

(

gdJpegInfo *

info

)

Initialize a gdJpegInfo structure with default values.

Parameters

info	Pointer to the gdJpegInfo structure to initialize.

gdJpegReadOptionsInit()

void gdJpegReadOptionsInit

(

gdJpegReadOptions *

options

)

Initialize JPEG read options with default values.

Parameters

options

Pointer to the gdJpegReadOptions structure to initialize.

gdJpegWriteOptionsInit()

void gdJpegWriteOptionsInit

(

gdJpegWriteOptions *

options

)

Initialize JPEG write options with default values.

Parameters

options

Pointer to the gdJpegWriteOptions structure to initialize.