使用GDI+保存位图文件为PNG文件

1.添加头文件

#include <ocidl.h>　　
#include <olectl.h>
#include <stdio.h>
#include <atlconv.h>

#include <GdiPlus.h>
using namespace Gdiplus;

#pragma comment( lib , "gdiplus.lib" )

2.添加COM初始化及GDI+初始化

CoInitialize( NULL );
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

3.功能函数

int GetImageCLSID(const   WCHAR*   format,   CLSID*   pCLSID)
{
    //得到格式为format的图像文件的编码值，访问该格式图像的COM组件的GUID值保存在pCLSID中
    UINT num = 0;
    UINT size = 0;

Gdiplus::ImageCodecInfo* pImageCodecInfo = NULL;
GetImageEncodersSize(&num, &size);

if(size == 0)
return FALSE; // 编码信息不可用

    //分配内存
    pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
    if(pImageCodecInfo == NULL)
        return FALSE;   //   分配失败

//获得系统中可用的编码方式的所有信息
GetImageEncoders(num, size, pImageCodecInfo);

    //在可用编码信息中查找format格式是否被支持
    for(UINT i = 0; i < num; ++i)
    {
        //MimeType：编码方式的具体描述
        if(wcscmp(pImageCodecInfo[i].MimeType, format) == 0)
        {
            *pCLSID = pImageCodecInfo[i].Clsid;
            free(pImageCodecInfo);
            return TRUE;
        }
    }

free(pImageCodecInfo);
return FALSE;
}

BOOL BmpToPNG( char* strBmpFile, char* strPngFile )
{
FILE* cbfBmp = fopen( strBmpFile, "rb" );
FILE* cbfImage = fopen( strPngFile, "wb" );

    fseek( cbfBmp, 0, SEEK_END );
    int iBmpSize = ftell( cbfBmp );
    fseek( cbfBmp, 0, SEEK_SET );
    HGLOBAL hMemBmp = GlobalAlloc(GMEM_FIXED, iBmpSize);
    if (hMemBmp == NULL) return FALSE;

    IStream* pStmBmp = NULL;
    CreateStreamOnHGlobal(hMemBmp, FALSE, &pStmBmp);
    if (pStmBmp == NULL)
    {
        GlobalFree(hMemBmp);