使用Ilj编解码Jpeg文件

2011-04-27 14:35:30|  分类： 技术系列 |  标签：jcprops  jerr  解码  dibchannels  lptemp    字号：大中小 订阅

首先 添加头文件 和 所需要的库

#include "IJL/include/ijl.h"

#pragma comment(lib,"IJL//lib//ijl15.lib")

1  解码。

原型： bool decodeFromJPEGBuffer(unsigned char* lpJpgBuffer,unsigned int dwJpgBufferSize,unsigned char** lppRgbBuffer,unsigned int* lpdwWidth,unsigned int* lpdwHeight,unsigned int* lpdwNumberOfChannels)

bool bres;
IJLERR jerr;
DWORD dwWholeImageSize;
BYTE* lpTemp = NULL;
JPEG_CORE_PROPERTIES jcprops;
bres = true;
__try
{
jerr = ijlInit(&jcprops);
if(IJL_OK != jerr)
{
bres = false;
__leave;
}
jcprops.JPGFile = NULL;
jcprops.JPGBytes = lpJpgBuffer;
jcprops.JPGSizeBytes = dwJpgBufferSize;
jerr = ijlRead(&jcprops, IJL_JBUFF_READPARAMS);
if(IJL_OK != jerr)
{
bres = false;
__leave;
}
switch(jcprops.JPGChannels)
{
case 1:
{
jcprops.JPGColor = IJL_G;
jcprops.DIBColor = IJL_BGR;
jcprops.DIBChannels = 3;
break;
}
case 3:
{
jcprops.JPGColor = IJL_YCBCR;
jcprops.DIBColor = IJL_BGR;
jcprops.DIBChannels = 3;
break;
}
default:
{
jcprops.JPGColor = IJL_OTHER;
jcprops.DIBColor = IJL_OTHER;
jcprops.DIBChannels = jcprops.JPGChannels;
break;
}
}
dwWholeImageSize = jcprops.JPGWidth * jcprops.JPGHeight *
jcprops.DIBChannels;
lpTemp = new BYTE [dwWholeImageSize];

注意 在解码中是 函数内部申请内存 在调用之后要释放掉
if(NULL == lpTemp)
{
bres = false;
__leave;
}
jcprops.DIBWidth = jcprops.JPGWidth;
jcprops.DIBHeight = jcprops.JPGHeight;
jcprops.DIBPadBytes = 0;
jcprops.DIBBytes = lpTemp;
jerr = ijlRead(&jcprops, IJL_JBUFF_READWHOLEIMAGE);
if(IJL_OK != jerr)
{
bres = false;
__leave;
}
}
__finally
{
if(FALSE == bres)
{
if(NULL != lpTemp)
{
delete [] lpTemp;
lpTemp = NULL;
}
}
ijlFree(&jcprops);
*lpdwWidth = jcprops.DIBWidth;
*lpdwHeight = jcprops.DIBHeight;
*lpdwNumberOfChannels = jcprops.DIBChannels;
*lppRgbBuffer = lpTemp;
}

return bres;

2  编码。

bool EncodeToJPEGBuffer(BYTE* pRgbBuffer,DWORD dwWidth,DWORD dwHeight,BYTE* pJpgBuffer,DWORD &dwJpgBufferSize)
// 源RGB数据 未对齐的（in）    图像宽度(in)  图像高度 (in)  编码后的JpegBuf(out)  JpegBuf的长度(out)  
{
DWORD   dwRgbBufferSize = dwWidth * dwHeight;//计算出存放图像数据的最大空间
预先算出最大的Jpg大小 
IJLERR jerr;

JPEG_CORE_PROPERTIES jcprops;

// Set up the info on the desired DIB properties.
ijlInit(&jcprops);
！！！初始化之后必须释放 否则内存泄漏

填充jcprops 结构体
jcprops.DIBBytes       = pRgbBuffer;

jcprops.DIBWidth       = dwWidth;

jcprops.DIBHeight      = dwHeight; // Implies a bottom-up DIB.

jcprops.DIBPadBytes    = 0;

jcprops.DIBChannels    = 3;//单通道图像表示一个字节就是一个像素，-3标识-3个字节表示一个像素

jcprops.DIBColor       = IJL_BGR;

jcprops.DIBSubsampling = IJL_NONE;//通道数决定的

//目标JPG图像的设置

jcprops.JPGFile        = NULL;
//  若直接产生JPG文档则填充该变量
jcprops.JPGSizeBytes   = dwRgbBufferSize;//Max buffer size.

jcprops.JPGWidth       = dwWidth;

jcprops.JPGHeight      = dwHeight;

jcprops.JPGChannels    = 3;

jcprops.JPGColor       = IJL_RGB;//灰度彩色空间Grayscale color space.

jcprops.JPGSubsampling = IJL_NONE; // 4:1:1 subsampling

jcprops.JPGBytes       = pJpgBuffer;//Pointer to buffer based JPEG.

jcprops.jquality          = 60; // Select "good" image quality【-100】

jerr =
ijlWrite(&jcprops,IJL_JBUFF_WRITEWHOLEIMAGE);

ijlFree(&jcprops );
if(IJL_OK != jerr)//发生错误提示信息

{

AfxMessageBox((LPCTSTR)ijlErrorStr(jerr),MB_OK,NULL);//ijlErrorStr---Return a pointer to a string with error description.

return FALSE;

}

dwJpgBufferSize = jcprops.JPGSizeBytes;//供外部引用，计算数据量的大小

return TRUE;

}

PS Endode部分的内存是自己提供的 不在内部分配 外部释放 和解码不太一样。 而送入的内存区大小不能小于 w*h 。 否则程序访问非法内存 就挂了

其中 IJL_DIB_PAD_BYTES  可以设置