Method createScaleString

libffmpegthumbnailer/moviedecoder.cpp:206–319

}

std::string MovieDecoder::createScaleString(const std::string& sizeString, bool maintainAspectRatio)
{
    int width            = -1;
    int height           = -1;
    bool pureNumericSize = true;

    if (sizeString.empty()) {
        return "w=0:h=0";
    }

    try {
        std::regex sizeRegex(R"r(([w|h])=(-?\d+)(?::([w|h])=(-?\d+))?)r");
        std::smatch baseMatch;
        if (std::regex_match(sizeString, baseMatch, sizeRegex)) {
            if (baseMatch.size() != 3 && baseMatch.size() != 5) {
                throw std::runtime_error("Failed to parse size string");
            }

            auto parseMatch = [&width, &height](std::smatch& match, size_t index) {
                auto specifier = match[index].str();
                if (specifier == "w") {
                    width = std::stoi(match[index + 1].str());
                    if (width <= 0) {
                        width = -1;
                    }
                } else if (specifier == "h") {
                    height = std::stoi(match[index + 1].str());
                    if (height <= 0) {
                        height = -1;
                    }
                }
            };

            pureNumericSize = false;
            if (baseMatch.size() >= 3) {
                parseMatch(baseMatch, 1);
            }

            if (baseMatch.size() == 5) {
                parseMatch(baseMatch, 3);
            }
        } else {
            width = std::stoi(sizeString);
        }
    } catch (const std::regex_error&) {
        throw std::runtime_error("Failed to parse size string");
    }

    std::stringstream scale;

    if (width != -1 && height != -1) {
        scale << "w=" << width << ":h=" << height;
        if (maintainAspectRatio) {
            scale << ":force_original_aspect_ratio=decrease";
        }
    } else if (!maintainAspectRatio) {
        if (width == -1) {
            scale << "w=" << height << ":h=" << height;