IJL庫之JPEG圖片壓縮
如何將比較大的圖片壓縮成比較小的圖片，通常在相機一直拍圖且需要將圖片網絡傳輸時，必須壓縮圖片。相機一般幾十FPS，每張幾M，只能用JPEG有順壓縮才能到可以實時傳輸要求。 還有就是這種特定情況壓縮需要保證 壓縮率 與 壓縮速度，那就是用Intel的IJL JPEG壓縮庫，網上有IJL15.DLL IJL20.DLL，15版本存在內存泄漏，用20版本即可。
例子：
exe執行程序 , ijl20x64.dll 放在同一級目錄下。
typedef IJLERR (*pInitFunc)(JPEG_CORE_PROPERTIES*); // ijlInit函數類型
typedef IJLERR (*pWriteFunc)(JPEG_CORE_PROPERTIES*,IJLIOTYPE); // ijlWrite函數類型
typedef IJLERR (*pFreeFunc)(JPEG_CORE_PROPERTIES*); // ijlFree函數類型
pInitFunc funcInit = NULL; // ijlInit 函數指針
pWriteFunc funcWrite = NULL; // ijlWrite 函數指針
pFreeFunc funcFree = NULL; // ijlFree 函數指針
char lpExeName[512] = {0};
HMODULE h = GetModuleHandle( NULL );
::GetModuleFileName( h,lpExeName,512 );
CString strExeName(lpExeName);
int nPos = strExeName.ReverseFind( ‘\\‘ );
CString strLeft,slibLeft,sDllName;
strLeft = strExeName.Left(nPos);
int n = strLeft.ReverseFind(‘\\‘);
slibLeft = strLeft.Left(n);
sDllName = slibLeft + "\\lib\\ijl20x64.dll" ; // ijl20x64.dll 的全路徑
m_hIjlModule = LoadLibrary(sDllName); // loadlibrary
// 加載IJL庫的函數
funcInit = (pInitFunc)GetProcAddress(m_hIjlModule,"ijlInit");
funcWrite = (pWriteFunc)GetProcAddress(m_hIjlModule,"ijlWrite");
funcFree = (pFreeFunc)GetProcAddress(m_hIjlModule,"ijlFree");
// 設置圖片參數
JPEG_CORE_PROPERTIES image;
IJLERR err;
IJLIOTYPE iotype = IJL_JBUFF_WRITEWHOLEIMAGE;
// JPEG 壓縮 Basler 4096*2048 的單通道黑白圖
unsigned char* saveBasler = (unsigned char*)malloc(4096*2048);
ZeroMemory(saveBasler,4096*2048);
ZeroMemory( &image, sizeof(JPEG_CORE_PROPERTIES));
funcInit( &image ); // 此處會開辟內存，後面對應要用funFree釋放
image.DIBWidth = 4096;
image.DIBHeight = 2048;
image.JPGBytes = (unsigned char*)saveBasler;
image.JPGSizeBytes = 8388608; // 4096*2048
image.JPGWidth = 4096;
image.JPGHeight = 2048;
image.jquality = 90;
image.DIBColor = IJL_G;
image.DIBChannels = 1; // 黑白色，如果是RGB真彩色，channel=3 圖片SIZE = width*height*3
image.DIBPadBytes = IJL_DIB_PAD_BYTES(image.DIBWidth,1);
image.JPGColor = IJL_G;
image.JPGChannels = 1;
image.JPGSubsampling = IJL_NONE;
image.DIBBytes = tmpBasler;
err = funcWrite (&image, iotype);
int nJpgLen = image.JPGSizeBytes; // 壓縮完成後 JPEG圖片的大小， 壓縮後數據在saveBasler 裏面，直接將saveBasler 寫入一個JPG文件即可，長度為nJpgLen.
funcFree(&image); // 釋放內存
IJL庫之JPEG圖片壓縮