vs2008中GDI+的使用方法

最新推荐文章于 2014-12-26 13:54:01 发布

转载最新推荐文章于 2014-12-26 13:54:01 发布 · 712 阅读

本文介绍两种将BMP格式图像转换为JPG格式的方法。方法一通过使用GDI+ API并设置压缩质量实现，提供了对压缩比的精确控制；方法二则利用CImage类进行转换，操作更为简便但无法调整压缩质量。

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将bmp转成jpg格式:

方法一(优点:能控制压缩比):
int GetEncoderClsid(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;
            free(pImageCodecInfo);
            return j;     //   Success
        }
    }
    free(pImageCodecInfo);
    return -1;     //   Failure
}

/****************BMP转JPG*********用法示例**************************
Bitmap newbitmap(L"d:\\d.bmp");//加载BMP
const unsigned short *pFileName=L"d:\\new.jpg";//保存路径
SaveFile(&newbitmap,pFileName );
************************************************************/
voidSaveFile(Bitmap* pImage, const wchar_t* pFileName)//
{
    EncoderParameters encoderParameters;
    CLSID jpgClsid;
GetEncoderClsid(L"image/jpeg", &jpgClsid);
    encoderParameters.Count = 1;
    encoderParameters.Parameter[0].Guid = EncoderQuality;
    encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
    encoderParameters.Parameter[0].NumberOfValues = 1;
    // Save the image as a JPEG with quality level 100.
    ULONG             quality;
    quality = 100;
    encoderParameters.Parameter[0].Value = &quality;
    Status status = pImage->Save(pFileName, &jpgClsid, &encoderParameters);
    if (status != Ok)
    {
        wprintf(L"%d Attempt to save %s failed.\n", status, pFileName);
    }
}

// 将当前屏幕保存成为jpg图片
// 参数   xs = 图象x轴大小,   ys = 图象y轴大小,   quality = jpeg图象质量
voidSaveCurScreenJpg(LPCWSTR   pszFileName,   int   xs,   int   ys,   int   quality)
{
    HWND hwnd = ::GetDesktopWindow();
    HDC hdc = GetWindowDC(NULL);
    int x = GetDeviceCaps(hdc, HORZRES);
    int y = GetDeviceCaps(hdc, VERTRES);
    HBITMAP hbmp = ::CreateCompatibleBitmap(hdc, x, y), hold;
    HDC hmemdc = ::CreateCompatibleDC(hdc);
    hold = (HBITMAP)::SelectObject(hmemdc,   hbmp);
    BitBlt(hmemdc, 0, 0, x, y, hdc, 0, 0, SRCCOPY);
    SelectObject(hmemdc, hold);

    Bitmap bit(xs, ys), bit2(hbmp, NULL);
    Graphics g(&bit);
    g.ScaleTransform((float)xs/x,   (float)ys/y);
    g.DrawImage(&bit2,   0,   0);

    CLSID                           encoderClsid;
    EncoderParameters   encoderParameters;

    encoderParameters.Count   =   1;
    encoderParameters.Parameter[0].Guid   =   EncoderQuality;
    encoderParameters.Parameter[0].Type   =   EncoderParameterValueTypeLong;
    encoderParameters.Parameter[0].NumberOfValues   =   1;
    encoderParameters.Parameter[0].Value   =   &quality;

    GetEncoderClsid(L"image/jpeg",   &encoderClsid);
    bit.Save(pszFileName,   &encoderClsid,   &encoderParameters);

    ::DeleteObject(hbmp);
    ::DeleteObject(hmemdc);
    return;
}

HBITMAP ReturnHBITMAP(CString   FileName)//FileName可能是bmp、dib、png、gif、jpeg/jpg、tiff、emf等文件的文件名
{
          Bitmap   tempBmp(FileName.AllocSysString())   ;
        Color       backColor;
        HBITMAP       HBitmap;
        tempBmp.GetHBITMAP(backColor,&HBitmap);
        return   HBitmap;
}

方法二(优点:简单;缺点:不能控制压缩比):
bool CCaptureWindow::SaevBitmapToJpg(HBITMAP hBitmap, LPCTSTR lpFileName)

{

CImage img;

img.Attach(hBitmap);

HRESULT hResult = img.Save(lpFileName);

DeleteObject(hBitmap);

return TRUE;

}