转：GetCodecClsid--提供多种转换功能的GDIPLUS

The GDI+

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This article was contributed by Leandro Gustavo Biss Becker - CEFET-PR.
Environment: [VC6 SP4, NT4 SP3, W2k, Win 9x]

I have found that the Microsft GDI+ can do many cool things for you. Previously you had to find code or write your own code to do the same things. One of these things is the ability to load or save the following types of images:

BMP
DIB
RLE
GIF
JPEG
EMF
TIFF
PNG
These can be loaded with just a few lines of code like this:

#include <Gdiplus.h>
using namespace Gdiplus;
#pragma comment(lib, "gdiplus.lib")

Image Im(L"c:\\fig.jpg", FALSE);
CLSID GifCodec;
GetCodecClsid(L"image/gif", &GifCodec);
Im.Save(L"c:\\fig.gif", &GifCodec, NULL);
Here is the code to GetCodecClsid

int GetCodecClsid(const WCHAR* format, CLSID* pClsid)
{
UINT num = 0; // number of image encoders
UINT size = 0; // size of the image encoder array in bytes

ImageCodecInfo* pImageCodecInfo = NULL;

GetImageEncodersSize(&num, &size);
if(size == 0)
return -1; // Failure

pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
if(pImageCodecInfo == NULL)
return -1; // Failure

GetImageEncoders(num, size, pImageCodecInfo);

for(UINT j = 0; j < num; ++j)
{
     if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
     {
       *pClsid = pImageCodecInfo[j].Clsid;
       return j; // Success
     }
} // for

return -1; // Failure
} // GetCodecClsid

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