ImageMagick++でサムネールに変換

C++はなんども挫折してるのだが、サムネール処理がいる、というのでMagick++を使ってみた。

#include <Magick++.h> 
#include <iostream> 

class ImageFactory {

public:
    ImageFactory(int width, int height);
    ~ImageFactory();
    void thumbnail(const char *source_image, const char *thumb_image);

private:
    Magick::Image image;
    Magick::Geometry size;
    int _width;
    int _height;
    float _ratio;
};

#include "ImageFactory.h"

using namespace std;
using namespace Magick;

ImageFactory::ImageFactory(int width, int height) {
    _width = width;
    _height = height;
    _ratio = (float) width / (float) height;
};

ImageFactory::~ImageFactory() {
};

void
ImageFactory::thumbnail(const char *source_image, const char *thumb_image) {
    float ratio;
    try {
        // Read a file into image object 
        image.read(source_image);

        size = image.size();
        if (size.height() != 0) {
            ratio = (float) size.width() / (float) size.height();
        }
        // Crop the image to specified size (width, height, xOffset, yOffset)
        if (ratio > _ratio) {
            // 横長：
            image.zoom(Geometry((int) (_height * ratio), _height, 0, 0));
            image.crop(Geometry(_width, _height,
                    (int) ((image.size().width() - _width) / 2), 0));
        } else {
            // 縦長：
            image.zoom(Geometry(_width, (int) (_width / ratio), 0, 0));
            image.crop(Geometry(_width, _height, 0,
                    (image.size().height() - _height) / 2));
        }

        image.magick("png");

        // Write the image to a file 
        image.write(thumb_image);
    } catch (Exception &error_) {
        cout << "Caught exception: " << error_.what() << endl;
    }
};