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FreeImageで画像の読み込みと保存

Last updated at Posted at 2016-01-30

C++で簡単に使える画像読み込みライブラリが欲しかったので。

Official site

対応フォーマット

http://freeimage.sourceforge.net/features.html のSUPPORTED FORMATを参照。有名どころは使える。

サンプル

#include<iostream>
#include<FreeImage.h>

int main() {
    std::cout << "FreeImage ver. " << FreeImage_GetVersion() << std::endl;
    std::cout << FreeImage_GetCopyrightMessage() << std::endl;

    try {
        // GIF画像を読み込み
        auto filename = "lena_color.gif";
        auto image    = std::shared_ptr<FIBITMAP>(
                            FreeImage_Load(FIF_GIF, filename, GIF_DEFAULT),FreeImage_Unload);
        if(!image) {
            throw std::runtime_error("Load failed");
        }

        // グレースケールに変換
        auto greyimg = std::shared_ptr<FIBITMAP>(
                            FreeImage_ConvertToGreyscale(image.get()),  FreeImage_Unload);
        if(!greyimg) {
            throw std::runtime_error("Convert failed");
        }

        // PNGとして保存
        if(!FreeImage_Save(FIF_PNG, greyimg.get(), "convert.png", PNG_DEFAULT)) {
            throw std::runtime_error("Save failed");
        }
    }
    catch(std::exception& e) {
        std::cout << "exception!\n" << e.what() << std::endl;
    }
}

ライブラリの初期化(FreeImage_Initialise)は動的リンクする場合は明示的な呼び出し不要。静的リンクの場合は一度だけ呼ばなければならない。FreeImage_DeInitializeも同様。

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