EncodeJPEGImage

#include "BIJPEG.H"

int CALLBACK EncodeJPEGImage( INT_PTR iFile,
JCompressInfo FAR* lpInfo
BOOL bICC)

Description

Compresses an image into a JPEG file. The raw image data must be passed to the function through the user defined callback function line by line.

Parameters

INT_PTR	iFile	Image file handle.
JCompressInfo FAR*	lpInfo	FAR pointer to JcompressInfo Structure.
BOOL	bICC	Enable or Disable use of ICC profiles.

typedef struct tagJCompressInfo

{

WORD	wWidth;	Width of image.
WORD	wHeight;	Height of image.
DWORD	dwXRes;	Image X Resolution in Pixel per meter.
DWORD	dwYRes;	Image Y Resolution in Pixel per meter.
WORD	wQuality;	Image Quality Factor can be between 1 - 100. if quality factor is set to 1 the output file is the smallest and the loss ratio is the largest. if quality factor is set to 100 the output file is the largest and the loss ratio is the smallest. Default value 75.
WORD	wColors;	Input colors 1 or 3. 1 - Input lines 8 bits per pixel grayscale. 3 - Input lines 24 bits per pixel true color.
BOOL	bGrayOutput;	If it is set to TRUE then it will convert 24 bit per pixel image to 8 bit grayscale output.
WORD	wXSubSampling;	Crominance components horizontal subsampling 1-2. The default is 2.
WORD	wYSubSampling;	Crominance component vertical subsampling 1-2. The default is 2.
WORD	wRestartInterval;	JPEG coder restart interval 0-65535 default 0. if parameter is not 0 jpeg compressor reset the compressor and place RestartIntervall marker to the output file. JPEG decompressor can decode images between two restart interval markers.
WORD	wHeaderType;	JPEG Application Marker type. JHDR_JFIF - JPEG Interchange file format using YCbCr color model. JHDR_G3FAX - CCITT T.4E JPEG File format using Lab color model.
INT_PTR	lUserData;	A pointer to a user defined data structure. It is passed to the callback function as a third parameter unchanged.
FILLPROC	lpLineFn;	Callback function which will pass the DIB lines to the compressor.
BOOL	bHPLabColor	Lab marker.
BOOL	bDNL	DNL marker.

} JCompressInfo;

Programming notes

The callback function pointed by the lpLineFn member of JCompressInfo must use the Pascal calling convention and must have the following form:

int CALLBACK LineFn(LPSTR lpLineBuff, int nLine, INT_PTR lParam)

LineFn is a placeholder for the application-supplied function name. You can use any other name for this purpose.

Parameters

LPSTR	lpLineBuff	Buffer to put a single line DIB into (of course, without header).
int	nLine	Index of the required line. Line numbers are started from zero.
INT_PTR	lParam	The lUserData member of the JCompressInfo structure passed to the EncodeJPEGImage() function. The user can use this parameter freely.

Return values

Returns 0 on success, else error code.

JERR_FILE Write to the file failed.

JERR_MEMORY Not enough memory.

JERR_COMPRESSION Error while compressing.

JERR_PARAMETER lpInfo is NULL.

JERR_NOLINEPROC lpLineFn is NULL.

JERR_COLORS The DIB is not a 24 bit color or 8 bit grayscale Image.

JERR_BAD_SUBSAMPLING wXSubSampling or wYSubSampling parameter is
not equal with 0,1 or 2. The 0 stands for the default
value only, it has no other meaning.

Requirements

Header : Declared in BiJpeg.h; include BiJpeg.h.

Library : Use BiJpeg.lib.

DLLs : BiJpeg.dll.

Code example

default values in JCompressInfo structure

Info.wXSubSampling = 2;

Info.wYSubSampling = 2;

Info.wQuality = 75;

Info.bGrayOutput = FALSE;

Info.wHeaderType = JHDR_JFIF;

Info.wRestartInterval = 0;