cocos2d-xでダウンロードした画像をファイルに保存せず表示する ref: http://qiita.com/gin0606/items/b498b016acbb212dc6f3

file0.cpp

auto url = "任意の画像のURL";
auto request = new cocos2d::network::HttpRequest();
request->setUrl(url);
request->setRequestType(cocos2d::network::HttpRequest::Type::GET);

request->setResponseCallback([this, url](cocos2d::network::HttpClient *, cocos2d::network::HttpResponse *response) {
    if (!response->isSucceed()) {return;}
    auto responseData = response->getResponseData();
    auto bytes = reinterpret_cast<unsigned char *>(&(responseData->front()));

    auto data = cocos2d::Data();
    data.copy(&(bytes.front()), bytes.size());

    auto image = new (std::nothrow) cocos2d::Image();
    if (!image) {return;}
    image->initWithImageData(data.getBytes(), data.getSize());
    auto texture = cocos2d::Director::getInstance()->getTextureCache()->addImage(image, url);

    auto spriteFrame = cocos2d::SpriteFrame::createWithTexture(texture, cocos2d::Rect(0, 0, texture->getContentSize().width, texture->getContentSize().height));
    cocos2d::SpriteFrameCache::getInstance()->addSpriteFrame(spriteFrame, url); 
    CC_SAFE_RELEASE(image);

    auto sprite = cocos2d::Sprite::createWithTexture(texture);
    this->addChild(sprite);
    // or
    auto imageView = cocos2d::ui::ImageView::create(url, cocos2d::ui::TextureResType::PLIST);
    this->addChild(imageView);
});
cocos2d::network::HttpClient::getInstance()->send(request);