Question

我正在编写在Windows上使用GDI +压缩图像的功能，并且它运行良好，

void ImageProcessorImpl::compressImpl(const std::string& path, int size, UInt8 quality)
{
    HBITMAP hbmReturn = NULL;
    Bitmap* bmPhoto = NULL;

    std::wstring upath;
    UnicodeConverter::toUTF16(path, upath);

    // make source file close automatically, Bitmap detructor will be called
    { 
        Bitmap image(upath.c_str());

        int srcWidth  = image.GetWidth();
        int srcHeight = image.GetHeight();

        float percent = 0;
        int destX = 0, destY = 0;
        if (srcWidth > srcHeight)
        {
            percent = ((float)size/(float)srcWidth);
            destX   = (int)((size - (srcWidth * percent))/2);
        }
        else
        {
            percent = ((float)size/(float)srcHeight);
            destY   = (int)((size - (srcHeight * percent))/2);
        }

        if (percent >= 1.0f)
            return; // skip compress

        int destWidth  = (int)(srcWidth * percent);
        int destHeight = (int)(srcHeight * percent);

        bmPhoto = new Bitmap(destWidth, destHeight, PixelFormat24bppRGB);
        bmPhoto->SetResolution(image.GetHorizontalResolution(), image.GetVerticalResolution());

        Graphics *grPhoto = Graphics::FromImage(bmPhoto);
        Color colorW(255, 255, 255, 255);
        grPhoto->Clear(colorW);
        grPhoto->SetInterpolationMode(InterpolationModeHighQualityBicubic);
        grPhoto->DrawImage(&image, Rect(destX, destY, destWidth, destHeight));

        bmPhoto->GetHBITMAP(colorW, &hbmReturn);
        delete grPhoto;
    } // end source image file, Bitmap image(upath.c_str());

    // find appropriate encoder, jpeg
    CLSID encoderClsid;
    getEncoderClsid(L"image/jpeg", &encoderClsid);

    // set output quality for jpeg alone
    EncoderParameters encoderParameters;
    setEncoderQuality(&encoderParameters, &quality);

    // output to image file with desired quality
    bmPhoto->Save(upath.c_str(), &encoderClsid, &encoderParameters);

    // release resources
    delete bmPhoto;
    DeleteObject(hbmReturn);
}

int ImageProcessorImpl::getEncoderClsid(const WCHAR* format, void* clsid)
{
    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)
        {
            *(CLSID*)clsid = pImageCodecInfo[j].Clsid;
            free(pImageCodecInfo);
            return j;    //Success
        }
    }

    free(pImageCodecInfo);
    return -1; // Failure
}

void ImageProcessorImpl::setEncoderQuality(void* params, UInt8* quality)
{
    EncoderParameters* encoderParams = (EncoderParameters*)params;
    encoderParams->Count = 1;
    encoderParams->Parameter[0].Guid = EncoderQuality;
    encoderParams->Parameter[0].Type = EncoderParameterValueTypeLong;
    encoderParams->Parameter[0].NumberOfValues = 1;

    encoderParams->Parameter[0].Value = quality;
}

但是，我想在linux上有这个功能，我不知道我可以使用哪些lib在linux上实现这样的功能，谁能帮帮我？日Thnx

Answer 1

您可以使用ImageMagick库或netpbm库。 Netpbm还具有操作图像的命令行工具。

Answer 2

OpenCV为所有类型的图像处理以及图像压缩等简单事物提供了易于使用的界面。对于图像压缩来说可能有点过分，但我想如果你打算用这些图像做其他事情，这可能会有所帮助。

如何在linux上压缩图像？

2 个答案: