diff --git a/.gitignore b/.gitignore
index 01bbf5a..46694a2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ downloads/
 utt.lock
 thumbnails/
 _fresh/
+lib/
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..55c16bf
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "extensions/utils"]
+	path = extensions/utils
+	url = https://github.com/lifegpc/c-utils
diff --git a/deno.json b/deno.json
index d8d99e1..25b08a9 100644
--- a/deno.json
+++ b/deno.json
@@ -19,7 +19,8 @@
             "config.json",
             "static/sw.js",
             "static/sw.meta.json",
-            "_fresh"
+            "_fresh",
+            "extensions/build"
         ]
     },
     "compilerOptions": {
diff --git a/extensions/.gitignore b/extensions/.gitignore
new file mode 100644
index 0000000..378eac2
--- /dev/null
+++ b/extensions/.gitignore
@@ -0,0 +1 @@
+build
diff --git a/extensions/CMakeLists.txt b/extensions/CMakeLists.txt
new file mode 100644
index 0000000..60e5283
--- /dev/null
+++ b/extensions/CMakeLists.txt
@@ -0,0 +1,9 @@
+cmake_minimum_required(VERSION 3.18)
+
+project(extensions)
+
+set(ENABLE_ICONV OFF CACHE BOOL "Libiconv is not needed.")
+add_subdirectory(utils)
+include_directories("${CMAKE_CURRENT_SOURCE_DIR}/utils")
+
+add_subdirectory(thumbnail)
diff --git a/extensions/cmake/FindAVCODEC.cmake b/extensions/cmake/FindAVCODEC.cmake
new file mode 100644
index 0000000..c55c536
--- /dev/null
+++ b/extensions/cmake/FindAVCODEC.cmake
@@ -0,0 +1,33 @@
+find_package(PkgConfig)
+if (PkgConfig_FOUND)
+    pkg_check_modules(PC_AVCODEC QUIET IMPORTED_TARGET GLOBAL libavcodec)
+endif()
+
+if (PC_AVCODEC_FOUND)
+    set(AVCODEC_FOUND TRUE)
+    set(AVCODEC_VERSION ${PC_AVCODEC_VERSION})
+    set(AVCODEC_VERSION_STRING ${PC_AVCODEC_STRING})
+    set(AVCODEC_LIBRARYS ${PC_AVCODEC_LIBRARIES})
+    if (USE_STATIC_LIBS)
+        set(AVCODEC_INCLUDE_DIRS ${PC_AVCODEC_STATIC_INCLUDE_DIRS})
+    else()
+        set(AVCODEC_INCLUDE_DIRS ${PC_AVCODEC_INCLUDE_DIRS})
+    endif()
+    if (NOT AVCODEC_INCLUDE_DIRS)
+        find_path(AVCODEC_INCLUDE_DIRS NAMES libavcodec/avcodec.h)
+    endif()
+    if (NOT TARGET AVCODEC::AVCODEC)
+        add_library(AVCODEC::AVCODEC ALIAS PkgConfig::PC_AVCODEC)
+    endif()
+else()
+    message(FATAL_ERROR "failed.")
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(AVCODEC
+    FOUND_VAR AVCODEC_FOUND
+    REQUIRED_VARS
+        AVCODEC_LIBRARYS
+        AVCODEC_INCLUDE_DIRS
+    VERSION_VAR AVCODEC_VERSION
+)
diff --git a/extensions/cmake/FindAVFORMAT.cmake b/extensions/cmake/FindAVFORMAT.cmake
new file mode 100644
index 0000000..1f18044
--- /dev/null
+++ b/extensions/cmake/FindAVFORMAT.cmake
@@ -0,0 +1,33 @@
+find_package(PkgConfig)
+if (PkgConfig_FOUND)
+    pkg_check_modules(PC_AVFORMAT QUIET IMPORTED_TARGET GLOBAL libavformat)
+endif()
+
+if (PC_AVFORMAT_FOUND)
+    set(AVFORMAT_FOUND TRUE)
+    set(AVFORMAT_VERSION ${PC_AVFORMAT_VERSION})
+    set(AVFORMAT_VERSION_STRING ${PC_AVFORMAT_STRING})
+    set(AVFORMAT_LIBRARYS ${PC_AVFORMAT_LIBRARIES})
+    if (USE_STATIC_LIBS)
+        set(AVFORMAT_INCLUDE_DIRS ${PC_AVFORMAT_STATIC_INCLUDE_DIRS})
+    else()
+        set(AVFORMAT_INCLUDE_DIRS ${PC_AVFORMAT_INCLUDE_DIRS})
+    endif()
+    if (NOT AVFORMAT_INCLUDE_DIRS)
+        find_path(AVFORMAT_INCLUDE_DIRS NAMES libavformat/avformat.h)
+    endif()
+    if (NOT TARGET AVFORMAT::AVFORMAT)
+        add_library(AVFORMAT::AVFORMAT ALIAS PkgConfig::PC_AVFORMAT)
+    endif()
+else()
+    message(FATAL_ERROR "failed.")
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(AVFORMAT
+    FOUND_VAR AVFORMAT_FOUND
+    REQUIRED_VARS
+        AVFORMAT_LIBRARYS
+        AVFORMAT_INCLUDE_DIRS
+    VERSION_VAR AVFORMAT_VERSION
+)
diff --git a/extensions/cmake/FindAVUTIL.cmake b/extensions/cmake/FindAVUTIL.cmake
new file mode 100644
index 0000000..be90604
--- /dev/null
+++ b/extensions/cmake/FindAVUTIL.cmake
@@ -0,0 +1,33 @@
+find_package(PkgConfig)
+if (PkgConfig_FOUND)
+    pkg_check_modules(PC_AVUTIL QUIET IMPORTED_TARGET GLOBAL libavutil)
+endif()
+
+if (PC_AVUTIL_FOUND)
+    set(AVUTIL_FOUND TRUE)
+    set(AVUTIL_VERSION ${PC_AVUTIL_VERSION})
+    set(AVUTIL_VERSION_STRING ${PC_AVUTIL_STRING})
+    set(AVUTIL_LIBRARYS ${PC_AVUTIL_LIBRARIES})
+    if (USE_STATIC_LIBS)
+        set(AVUTIL_INCLUDE_DIRS ${PC_AVUTIL_STATIC_INCLUDE_DIRS})
+    else()
+        set(AVUTIL_INCLUDE_DIRS ${PC_AVUTIL_INCLUDE_DIRS})
+    endif()
+    if (NOT AVUTIL_INCLUDE_DIRS)
+        find_path(AVUTIL_INCLUDE_DIRS NAMES libavutil/avutil.h)
+    endif()
+    if (NOT TARGET AVUTIL::AVUTIL)
+        add_library(AVUTIL::AVUTIL ALIAS PkgConfig::PC_AVUTIL)
+    endif()
+else()
+    message(FATAL_ERROR "failed.")
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(AVUTIL
+    FOUND_VAR AVUTIL_FOUND
+    REQUIRED_VARS
+        AVUTIL_LIBRARYS
+        AVUTIL_INCLUDE_DIRS
+    VERSION_VAR AVUTIL_VERSION
+)
diff --git a/extensions/cmake/FindSWSCALE.cmake b/extensions/cmake/FindSWSCALE.cmake
new file mode 100644
index 0000000..49c5d98
--- /dev/null
+++ b/extensions/cmake/FindSWSCALE.cmake
@@ -0,0 +1,32 @@
+find_package(PkgConfig)
+if (PkgConfig_FOUND)
+    pkg_check_modules(PC_SWSCALE QUIET IMPORTED_TARGET GLOBAL libswscale)
+endif()
+
+if (PC_SWSCALE_FOUND)
+    set(SWSCALE_FOUND TRUE)
+    set(SWSCALE_VERSION ${PC_SWSCALE_VERSION})
+    set(SWSCALE_VERSION_STRING ${PC_SWSCALE_STRING})
+    set(SWSCALE_LIBRARYS ${PC_SWSCALE_LIBRARIES})
+    if (USE_STATIC_LIBS)
+        set(SWSCALE_INCLUDE_DIRS ${PC_SWSCALE_STATIC_INCLUDE_DIRS})
+    else()
+        set(SWSCALE_INCLUDE_DIRS ${PC_SWSCALE_INCLUDE_DIRS})
+    endif()
+    if (NOT SWSCALE_INCLUDE_DIRS)
+        find_path(SWSCALE_INCLUDE_DIRS NAMES libswscale/swscale.h)
+    endif()
+    if (NOT TARGET SWSCALE::SWSCALE)
+        add_library(SWSCALE::SWSCALE ALIAS PkgConfig::PC_SWSCALE)
+    endif()
+else()
+    message(FATAL_ERROR "failed.")
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(SWSCALE
+    FOUND_VAR SWSCALE_FOUND
+    REQUIRED_VARS
+        SWSCALE_LIBRARYS
+    VERSION_VAR SWSCALE_VERSION
+)
diff --git a/extensions/thumbnail/CMakeLists.txt b/extensions/thumbnail/CMakeLists.txt
new file mode 100644
index 0000000..4ddce30
--- /dev/null
+++ b/extensions/thumbnail/CMakeLists.txt
@@ -0,0 +1,28 @@
+cmake_minimum_required(VERSION 3.18)
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")
+
+project(thumbnail)
+if (MSVC)
+    add_compile_options(/utf-8)
+endif()
+
+if (NOT TARGET utils)
+    add_subdirectory("${CMAKE_CURRENT_SOURCE_DIR}/../utils" "${CMAKE_BINARY_DIR}/utils")
+    include_directories("${CMAKE_CURRENT_SOURCE_DIR}/../utils")
+endif()
+
+find_package(AVFORMAT 58 REQUIRED)
+find_package(AVCODEC 58 REQUIRED)
+find_package(AVUTIL 56 REQUIRED)
+find_package(SWSCALE 5 REQUIRED)
+
+include(GNUInstallDirs)
+
+add_library(thumbnail SHARED thumbnail.h thumbnail.c)
+target_link_libraries(thumbnail AVFORMAT::AVFORMAT)
+target_link_libraries(thumbnail AVCODEC::AVCODEC)
+target_link_libraries(thumbnail AVUTIL::AVUTIL)
+target_link_libraries(thumbnail SWSCALE::SWSCALE)
+target_link_libraries(thumbnail utils)
+
+install(TARGETS thumbnail)
diff --git a/extensions/thumbnail/thumbnail.c b/extensions/thumbnail/thumbnail.c
new file mode 100644
index 0000000..eea51ca
--- /dev/null
+++ b/extensions/thumbnail/thumbnail.c
@@ -0,0 +1,329 @@
+#include "thumbnail.h"
+#include "cfileop.h"
+#include "libavformat/avformat.h"
+#include "libavcodec/avcodec.h"
+#include "libswscale/swscale.h"
+#include <string.h>
+
+PUBLIC_API void thumbnail_fferror(int e, char* buf, size_t bufsize) {
+    if (!buf) return;
+    av_make_error_string(buf, bufsize, e);
+}
+
+int thumbnail_convert_frame(THUMBNAIL_ERROR* err, AVFrame* ifr, AVFrame** ofr, AVCodecContext* occ, THUMBNAIL_METHOD method) {
+    if (!err || !ifr || !ofr) return 1;
+    int re = 0;
+    struct SwsContext* sws = NULL;
+    AVFrame* fr = NULL, * fr2 = NULL;
+    if (!(fr = av_frame_alloc())) {
+        err->e = THUMBNAIL_OOM;
+        re = 1;
+        goto end;
+    }
+    int theight = ifr->height * occ->width / ifr->width;
+    char simple_way = 0;
+    if (occ->height == theight || method == THUMBNAIL_FILL) {
+        simple_way = 1;
+    }
+    if (simple_way) {
+        fr->width = occ->width;
+        fr->height = occ->height;
+        fr->format = occ->pix_fmt;
+        fr->sample_aspect_ratio = ifr->sample_aspect_ratio;
+    }
+    if ((err->fferr = av_frame_get_buffer(fr, 0)) < 0) {
+        err->e = THUMBNAIL_FFMPEG_ERROR;
+        re = 1;
+        av_log(NULL, AV_LOG_ERROR, "Failed to get buffer for output frame: %s\n", av_err2str(err->fferr));
+        goto end;
+    }
+    if ((err->fferr = av_frame_make_writable(fr)) < 0) {
+        err->e = THUMBNAIL_FFMPEG_ERROR;
+        re = 1;
+        av_log(NULL, AV_LOG_ERROR, "Failed to make writeable for output frame: %s\n", av_err2str(err->fferr));
+        goto end;
+    }
+    if (simple_way) {
+        if (!(sws = sws_getContext(ifr->width, ifr->height, (enum AVPixelFormat)ifr->format, fr->width, fr->height, (enum AVPixelFormat)fr->format, SWS_BILINEAR, NULL, NULL, NULL))) {
+            err->e = THUMBNAIL_UNABLE_SCALE;
+            re = 1;
+            goto end;
+        }
+        if ((err->fferr = sws_scale(sws, (const uint8_t* const*)ifr->data, ifr->linesize, 0, ifr->height, fr->data, fr->linesize)) < 0) {
+            err->e = THUMBNAIL_UNABLE_SCALE;
+            re = 1;
+            goto end;
+        }
+    }
+end:
+    if (re == 1 && fr) av_frame_free(&fr);
+    else if (re == 0) *ofr = fr;
+    if (fr2) av_frame_free(&fr2);
+    if (sws) sws_freeContext(sws);
+    return re;
+}
+
+int thumbnail_encode_video(THUMBNAIL_ERROR* err, AVFrame* ofr, AVFormatContext* oc, AVCodecContext* occ, char* writed_data) {
+    if (!err || !oc || !occ || !writed_data) return 1;
+    int re = 0;
+    AVPacket* pkt = av_packet_alloc();
+    if (!pkt) {
+        err->e = THUMBNAIL_OOM;
+        re = 1;
+        goto end;
+    }
+    *writed_data = 0;
+    if (ofr) {
+        ofr->pts = 0;
+        ofr->pkt_dts = 0;
+    }
+    if ((err->fferr = avcodec_send_frame(occ, ofr)) < 0) {
+        if (err->fferr == AVERROR_EOF) {
+            err->fferr = 0;
+        } else {
+            av_log(NULL, AV_LOG_ERROR, "Failed to send frame to encoder: %s\n", av_err2str(err->fferr));
+            err->e = THUMBNAIL_FFMPEG_ERROR;
+            re = 1;
+            goto end;
+        }
+    }
+    err->fferr = avcodec_receive_packet(occ, pkt);
+    if (err->fferr >= 0) {
+        *writed_data = 1;
+    } else if (err->fferr == AVERROR_EOF || err->fferr == AVERROR(EAGAIN)) {
+        err->fferr = 0;
+        goto end;
+    } else {
+        av_log(NULL, AV_LOG_ERROR, "Failed to recive data from encoder: %s\n", av_err2str(err->fferr));
+        err->e = THUMBNAIL_FFMPEG_ERROR;
+        re = 1;
+        goto end;
+    }
+    if (*writed_data && pkt) {
+        pkt->stream_index = 0;
+        if ((err->fferr = av_write_frame(oc, pkt)) < 0) {
+            err->e = THUMBNAIL_FFMPEG_ERROR;
+            av_log(NULL, AV_LOG_ERROR, "Failed to write data to muxer: %s\n", av_err2str(err->fferr));
+            re = 1;
+            goto end;
+        }
+    }
+end:
+    if (pkt) av_packet_free(&pkt);
+    return re;
+}
+
+THUMBNAIL_ERROR gen_thumbnail(const char* src, const char* dest, int width, int height, THUMBNAIL_METHOD method) {
+    THUMBNAIL_ERROR re = { THUMBNAIL_OK, 0 };
+    AVFormatContext* ic = NULL, * oc = NULL;
+    AVStream* is = NULL, * os = NULL;
+    const AVCodec* input_codec = NULL, * output_codec = NULL;
+    AVCodecContext* icc = NULL, * occ = NULL;
+    AVPacket pkt;
+    AVFrame* ifr = NULL, * ofr = NULL;
+    if (method < THUMBNAIL_COVER || method > THUMBNAIL_FILL) {
+        re.e = THUMBNAIL_UNKNOWN_METHOD;
+        goto end;
+    }
+    if (!src || !dest) {
+        re.e = THUMBNAIL_NULL_POINTER;
+        goto end;
+    }
+    if (fileop_exists(dest)) {
+        if (!fileop_remove(dest)) {
+            re.e = THUMBNAIL_REMOVE_OUTPUT_FILE_FAILED;
+            goto end;
+        }
+    }
+    if ((re.fferr = avformat_open_input(&ic, src, NULL, NULL)) < 0) {
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        av_log(NULL, AV_LOG_ERROR, "Failed to open file: %s\n", av_err2str(re.fferr));
+        goto end;
+    }
+    if ((re.fferr = avformat_find_stream_info(ic, NULL)) < 0) {
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        av_log(NULL, AV_LOG_ERROR, "Failed to find stream info in file: %s\n", av_err2str(re.fferr));
+        goto end;
+    }
+    for (unsigned int i = 0; i < ic->nb_streams; i++) {
+        AVStream* s = ic->streams[i];
+        if (s->codecpar && s->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
+            is = s;
+            break;
+        }
+    }
+    if (!is) {
+        re.e = THUMBNAIL_NO_VIDEO_STREAM;
+        goto end;
+    }
+    if ((re.fferr = avformat_alloc_output_context2(&oc, NULL, "mjpeg", dest)) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Failed to allocate output context: %s\n", av_err2str(re.fferr));
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        goto end;
+    }
+    if (!(input_codec = avcodec_find_decoder(is->codecpar->codec_id))) {
+        re.e = THUMBNAIL_NO_DECODER;
+        goto end;
+    }
+    if (!(icc = avcodec_alloc_context3(input_codec))) {
+        re.e = THUMBNAIL_OOM;
+        goto end;
+    }
+    if ((re.fferr = avcodec_parameters_to_context(icc, is->codecpar)) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Failed to copy decode parameters: %s\n", av_err2str(re.fferr));
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        goto end;
+    }
+    if ((re.fferr = avcodec_open2(icc, input_codec, NULL)) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Failed to open decoder: %s\n", av_err2str(re.fferr));
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        goto end;
+    }
+    output_codec = avcodec_find_encoder(AV_CODEC_ID_MJPEG);
+    if (!output_codec) {
+        re.e = THUMBNAIL_NO_ENCODER;
+        goto end;
+    }
+    if (!(occ = avcodec_alloc_context3(output_codec))) {
+        re.e = THUMBNAIL_OOM;
+        goto end;
+    }
+    occ->width = width;
+    occ->height = height;
+    occ->pix_fmt = AV_PIX_FMT_YUVJ420P;
+    occ->sample_aspect_ratio = icc->sample_aspect_ratio;
+    occ->time_base = AV_TIME_BASE_Q;
+    occ->color_range = AVCOL_RANGE_JPEG;
+    if ((re.fferr = avcodec_open2(occ, output_codec, NULL)) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Failed to open encoder: %s\n", av_err2str(re.fferr));
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        goto end;
+    }
+    if (!(os = avformat_new_stream(oc, NULL))) {
+        re.e = THUMBNAIL_OOM;
+        goto end;
+    }
+    if ((re.fferr = avcodec_parameters_from_context(os->codecpar, occ)) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Failed to copy encoder's params to muxer: %s\n", av_err2str(re.fferr));
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        goto end;
+    }
+    if (!(oc->oformat->flags & AVFMT_NOFILE)) {
+        if ((re.fferr = avio_open(&oc->pb, dest, AVIO_FLAG_WRITE)) < 0) {
+            av_log(NULL, AV_LOG_ERROR, "Failed to open output file: %s\n", av_err2str(re.fferr));
+            re.e = THUMBNAIL_FFMPEG_ERROR;
+            goto end;
+        }
+    }
+    if ((re.fferr = avformat_write_header(oc, NULL)) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Failed to write headers to file: %s\n", av_err2str(re.fferr));
+        re.e = THUMBNAIL_FFMPEG_ERROR;
+        goto end;
+    }
+    while (1) {
+        if ((re.fferr = av_read_frame(ic, &pkt)) < 0) {
+            av_log(NULL, AV_LOG_ERROR, "Failed to read frames from file: %s\n", av_err2str(re.fferr));
+            re.e = THUMBNAIL_FFMPEG_ERROR;
+            goto end;
+        }
+        if (pkt.data == NULL) {
+            av_packet_unref(&pkt);
+            av_log(NULL, AV_LOG_ERROR, "No data find in frames: %s\n", av_err2str(re.fferr));
+            re.e = THUMBNAIL_FFMPEG_ERROR;
+            goto end;
+        }
+        if (pkt.stream_index != is->index) {
+            av_packet_unref(&pkt);
+            continue;
+        }
+        if (!(ifr = av_frame_alloc())) {
+            av_packet_unref(&pkt);
+            re.e = THUMBNAIL_OOM;
+            goto end;
+        }
+        if ((re.fferr = avcodec_send_packet(icc, &pkt)) < 0) {
+            av_packet_unref(&pkt);
+            av_log(NULL, AV_LOG_ERROR, "Failed to send packet to decoder: %s\n", av_err2str(re.fferr));
+            re.e = THUMBNAIL_FFMPEG_ERROR;
+            goto end;
+        }
+        if ((re.fferr = avcodec_receive_frame(icc, ifr)) < 0) {
+            if (re.fferr == AVERROR(EAGAIN)) {
+                av_packet_unref(&pkt);
+                re.fferr = 0;
+                continue;
+            }
+            av_packet_unref(&pkt);
+            av_log(NULL, AV_LOG_ERROR, "Failed to receive frame from decoder: %s\n", av_err2str(re.fferr));
+            re.e = THUMBNAIL_FFMPEG_ERROR;
+            goto end;
+        }
+        if (thumbnail_convert_frame(&re, ifr, &ofr, occ, method)) {
+            av_packet_unref(&pkt);
+            re.e = THUMBNAIL_FFMPEG_ERROR;
+            goto end;
+        }
+        char writed = 0;
+        if (thumbnail_encode_video(&re, ofr, oc, occ, &writed)) {
+            av_packet_unref(&pkt);
+            goto end;
+        }
+        while (1) {
+            if (thumbnail_encode_video(&re, NULL, oc, occ, &writed)) {
+                av_packet_unref(&pkt);
+                goto end;
+            }
+            if (!writed) break;
+        }
+        av_packet_unref(&pkt);
+        break;
+    }
+    av_write_trailer(oc);
+end:
+    if (ifr) av_frame_free(&ifr);
+    if (ofr) av_frame_free(&ofr);
+    if (icc) avcodec_free_context(&icc);
+    if (occ) avcodec_free_context(&occ);
+    if (oc) {
+        if (!(oc->oformat->flags & AVFMT_NOFILE)) avio_closep(&oc->pb);
+        avformat_free_context(oc);
+    }
+    if (ic) avformat_close_input(&ic);
+    return re;
+}
+
+const char* thumbnail_berror(THUMBNAIL_ERROR_E e) {
+    switch (e) {
+    case THUMBNAIL_OK:
+        return "OK";
+    case THUMBNAIL_FFMPEG_ERROR:
+        return "A error occured in ffmpeg code.";
+    case THUMBNAIL_NULL_POINTER:
+        return "Arguments have null pointers.";
+    case THUMBNAIL_REMOVE_OUTPUT_FILE_FAILED:
+        return "Can not remove output file.";
+    case THUMBNAIL_NO_VIDEO_STREAM:
+        return "Can not find video stream in source file.";
+    case THUMBNAIL_OOM:
+        return "Out of memory.";
+    case THUMBNAIL_NO_DECODER:
+        return "No available decoder.";
+    case THUMBNAIL_NO_ENCODER:
+        return "No available encoder.";
+    case THUMBNAIL_UNABLE_SCALE:
+        return "Unable to scale image.";
+    default:
+        return "Unknown error.";
+    }
+}
+
+void thumbnail_error(THUMBNAIL_ERROR e, char* buf, size_t bufsize) {
+    switch (e.e) {
+    case THUMBNAIL_FFMPEG_ERROR:
+        thumbnail_fferror(e.fferr, buf, bufsize);
+        break;
+    default:
+        strncpy(buf, thumbnail_berror(e.e), bufsize);
+        break;
+    }
+}
diff --git a/extensions/thumbnail/thumbnail.h b/extensions/thumbnail/thumbnail.h
new file mode 100644
index 0000000..ba83365
--- /dev/null
+++ b/extensions/thumbnail/thumbnail.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <stddef.h>
+#define PUBLIC_API __declspec(dllexport)
+
+typedef enum THUMBNAIL_ERROR_E {
+    THUMBNAIL_OK,
+    THUMBNAIL_NULL_POINTER,
+    THUMBNAIL_REMOVE_OUTPUT_FILE_FAILED,
+    THUMBNAIL_FFMPEG_ERROR,
+    THUMBNAIL_NO_VIDEO_STREAM,
+    THUMBNAIL_UNKNOWN_METHOD,
+    THUMBNAIL_NO_DECODER,
+    THUMBNAIL_OOM,
+    THUMBNAIL_NO_ENCODER,
+    THUMBNAIL_UNABLE_SCALE,
+} THUMBNAIL_ERROR_E;
+
+typedef struct THUMBNAIL_ERROR {
+    THUMBNAIL_ERROR_E e;
+    int fferr;
+}THUMBNAIL_ERROR;
+
+typedef enum THUMBNAIL_METHOD {
+    THUMBNAIL_COVER = 1,
+    THUMBNAIL_CONTAIN,
+    THUMBNAIL_FILL,
+} THUMBNAIL_METHOD;
+
+PUBLIC_API THUMBNAIL_ERROR gen_thumbnail(const char* src, const char* dest, int width, int height, THUMBNAIL_METHOD method);
+PUBLIC_API void thumbnail_error(THUMBNAIL_ERROR e, char* buf, size_t bufsize);
diff --git a/extensions/utils b/extensions/utils
new file mode 160000
index 0000000..40e3df5
--- /dev/null
+++ b/extensions/utils
@@ -0,0 +1 @@
+Subproject commit 40e3df54a92500264f48359811bb5bb641bd01c4
diff --git a/import_map.json b/import_map.json
index c31e034..969d33c 100644
--- a/import_map.json
+++ b/import_map.json
@@ -27,6 +27,7 @@
         "@material/web/": "https://unpkg.lifegpc.workers.dev/@material/web@1.0.0-pre.13/",
         "@lit-labs/react/": "https://esm.sh/@lit-labs/react@1.2.1/",
         "bootstrap/": "https://esm.sh/bootstrap@5.3.0/",
-        "filesize": "https://esm.sh/filesize@10.0.7"
+        "filesize": "https://esm.sh/filesize@10.0.7",
+        "pwn/": "https://deno.land/x/pwn@1.0.0/"
     }
 }
diff --git a/routes/api/thumbnail/[id].ts b/routes/api/thumbnail/[id].ts
index 5fd4cd9..2195466 100644
--- a/routes/api/thumbnail/[id].ts
+++ b/routes/api/thumbnail/[id].ts
@@ -2,7 +2,11 @@ import { Handlers } from "$fresh/server.ts";
 import { exists } from "std/fs/exists.ts";
 import { get_task_manager } from "../../../server.ts";
 import { parse_bool, parse_int } from "../../../server/parse_form.ts";
-import { generate_filename, ThumbnailConfig } from "../../../thumbnail/base.ts";
+import {
+    generate_filename,
+    ThumbnailConfig,
+    ThumbnailGenMethod,
+} from "../../../thumbnail/base.ts";
 import { sure_dir } from "../../../utils.ts";
 import { ThumbnailMethod } from "../../../config.ts";
 import { fb_generate_thumbnail } from "../../../thumbnail/ffmpeg_binary.ts";
@@ -35,7 +39,12 @@ export const handler: Handlers = {
         const height = await parse_int(u.searchParams.get("height"), null);
         const quality = await parse_int(u.searchParams.get("quality"), 1);
         const force = await parse_bool(u.searchParams.get("force"), false);
-        const cfg: ThumbnailConfig = { width: 0, height: 0, quality };
+        const cfg: ThumbnailConfig = {
+            width: 0,
+            height: 0,
+            quality,
+            method: ThumbnailGenMethod.Unknown,
+        };
         if (width !== null && height !== null) {
             cfg.width = width;
             cfg.height = height;
diff --git a/thumbnail/base.ts b/thumbnail/base.ts
index ac34640..b450330 100644
--- a/thumbnail/base.ts
+++ b/thumbnail/base.ts
@@ -2,10 +2,18 @@ import { join } from "std/path/mod.ts";
 import { filterFilename } from "../utils.ts";
 import type { EhFile } from "../db.ts";
 
+export enum ThumbnailGenMethod {
+    Unknown,
+    Cover,
+    Contain,
+    Fill,
+}
+
 export type ThumbnailConfig = {
     width: number;
     height: number;
     quality: number;
+    method: ThumbnailGenMethod;
 };
 
 export function generate_filename(
@@ -13,10 +21,22 @@ export function generate_filename(
     f: EhFile,
     cfg: ThumbnailConfig,
 ) {
+    let method = "";
+    switch (cfg.method) {
+        case ThumbnailGenMethod.Cover:
+            method = "-cover";
+            break;
+        case ThumbnailGenMethod.Contain:
+            method = "-contain";
+            break;
+        case ThumbnailGenMethod.Fill:
+            method = "-fill";
+            break;
+    }
     return join(
         base,
         filterFilename(
-            `${f.id}-${f.token}-${cfg.width}x${cfg.height}-q${cfg.quality}.jpg`,
+            `${f.id}-${f.token}-${cfg.width}x${cfg.height}-q${cfg.quality}${method}.jpg`,
         ),
     );
 }
diff --git a/thumbnail/ffmpeg_api.ts b/thumbnail/ffmpeg_api.ts
new file mode 100644
index 0000000..233d178
--- /dev/null
+++ b/thumbnail/ffmpeg_api.ts
@@ -0,0 +1,68 @@
+/// <reference lib="deno.unstable" />
+import { Struct } from "pwn/mod.ts";
+import { ThumbnailGenMethod } from "./base.ts";
+
+let libSuffix = "";
+let libPrefix = "lib";
+switch (Deno.build.os) {
+    case "windows":
+        libSuffix = "dll";
+        libPrefix = "";
+        break;
+    case "darwin":
+        libSuffix = "dylib";
+        break;
+    default:
+        libSuffix = "so";
+        break;
+}
+
+let libPath = import.meta.resolve(`../lib/${libPrefix}thumbnail.${libSuffix}`)
+    .slice(7);
+if (Deno.build.os === "windows") {
+    libPath = libPath.slice(1);
+}
+
+const lib = Deno.dlopen(
+    libPath,
+    {
+        "gen_thumbnail": {
+            "parameters": ["buffer", "buffer", "i32", "i32", "i32"],
+            "result": { struct: ["i32", "i32"] },
+            "nonblocking": true,
+        },
+        "thumbnail_error": {
+            "parameters": [{ struct: ["i32", "i32"] }, "buffer", "usize"],
+            "result": "void",
+        },
+    } as const,
+);
+const _Result = new Struct({ e: "s32", fferr: "s32" });
+
+function get_error(fferr: Uint8Array) {
+    const u = new Uint8Array(64);
+    lib.symbols.thumbnail_error(fferr, u, u.length);
+    let len = u.findIndex((i) => i === 0);
+    if (len === -1) len = u.length;
+    return (new TextDecoder()).decode(u.slice(0, len));
+}
+
+export async function gen_thumbnail(
+    src: string,
+    dest: string,
+    width: number,
+    height: number,
+    method: ThumbnailGenMethod,
+) {
+    const t = new TextEncoder();
+    const ore = await lib.symbols.gen_thumbnail(
+        t.encode(`${src}\0`),
+        t.encode(`${dest}\0`),
+        width,
+        height,
+        method,
+    );
+    const re = _Result.unpack(ore);
+    if (re.e) return get_error(ore);
+    return;
+}