lottie thumbnailer

CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(lottiethumb)

list(APPEND CMAKE_PREFIX_PATH "/usr/share/quazip")

set(CMAKE_CXX_STANDARD 14)

find_package(rlottie REQUIRED)
find_package(Qt5 COMPONENTS Gui REQUIRED)
find_package(QuaZip5 REQUIRED)

include_directories(${QUAZIP_INCLUDE_DIRS})

add_executable(lottiethumb main.cpp)
target_link_libraries(lottiethumb rlottie Qt5::Gui ${QUAZIP_LIBRARIES})

main.cpp

#include <iostream>
#include <rlottie.h>
#include <QImage>
#include <quagzipfile.h>
#include <QDebug>
#include <cmath>

int main(int argc, char **argv)
{

    // help text stuff start

    // if you delete this test, you can hardcode default in/out filenames
    if (argc < 3) {
        std::cout << "Usage: " << argv[0] << "<infilename.json> <outfilename.webp> [width] [height] [percentage]\n"
        << "Create a thumbnail for infilename.json at outfilename.webp, of size [width] pixels by [height] pixels.\n"
        << "Optionally, create the thumbnail on the frame at the [percentage] playback progress mark.\n"
        << "Output file format is determined by output filename and installed QImageCodecs.\n";
        exit(2);
    }

    // help text stuff end, defaults start

    QString inName = argc > 1 ? argv[1] : "/tmp/AnimatedSticker.tgs";
    QString outName = argc > 2 ? argv[2] : "/tmp/stick.webp";

    int width = argc > 3 ? atoi(argv[3]) : 512;
    width = width > 0 ? width : 512;
    int height = argc > 4 ? atoi(argv[4]) : 512;
    height = height > 0 ? height : 512;

    double selected = argc > 5 ? atoi(argv[5]) : 80;
    selected = fmod(selected, 100);
    selected = selected > 0 ? selected : 80;
    selected = 100 / selected;


    // defaults end, business logic start
    QuaGzipFile lottiefile(inName);
    lottiefile.open(QIODevice::ReadOnly);

    // This format is the default used by rlottie anyway
    QImage pic(width, height, QImage::Format_ARGB32_Premultiplied);

    // rlottie can render to a surface if it looks liek this
    auto buffer = std::make_unique<uint32_t[]>(width * height);
    // so we load the animation (the input file)
    auto animation = rlottie::Animation::loadFromData(lottiefile.readAll().toStdString(), inName.toStdString());

    // then we load up our frame from the animation into buffer...
    rlottie::Surface surface(buffer.get(), width, height, width * 4);
    animation->renderSync((animation->totalFrame() / selected), surface);


    // give it a gentle massage to get it into QImage
    for (int i = 0; i < width * height; i++) {
        if (buffer.get()[i]) {
            pic.setPixelColor(i % width, i / height, QColor(buffer.get()[i]));
        } else {
            // an int value of straight-up "0" is our transparent (background) colour
            pic.setPixelColor(i % width, i / height, QColor(0, 0, 0, 0));
        }
    }

    // Qt will magically spit out whatever image format is implied by the file extension
    if (pic.save(outName)) {
        return 0;
    } else {
        return 1;
    }
}

Very crashable :) I don't check for sanity on any of the files going in (right now) so you can pass in a malformed file and get a segfault. Just heads-up in case I don't come back and fix it up