misc: quantize png images to reduce filesize

Author: jsm174

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       - run: |
           sudo apt-get update
-          sudo apt-get install libsdl2-dev libsdl2-image-dev
+          sudo apt-get install libsdl2-dev libsdl2-image-dev libimagequant-dev
       - uses: actions/checkout@v3
       - name: Build
         run: |

CMakeLists.txt

@@ -8,25 +8,44 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
 
 find_package(PkgConfig REQUIRED)
 find_package(X11 REQUIRED)
+find_package(OpenMP REQUIRED)
 
 pkg_check_modules(SDL2 REQUIRED sdl2)
 pkg_check_modules(SDL2_IMAGE REQUIRED SDL2_image)
+pkg_check_modules(IMAGEQUANT REQUIRED imagequant)
+
+include_directories(
+   ${CMAKE_SOURCE_DIR}
+   ${X11_INCLUDE_DIR}
+   ${SDL2_INCLUDE_DIRS}
+   ${SDL2_IMAGE_INCLUDE_DIRS}
+   ${IMAGEQUANT_INCLUDE_DIRS}
+)
 
-include_directories(${CMAKE_SOURCE_DIR} ${X11_INCLUDE_DIR} ${SDL2_INCLUDE_DIRS} ${SDL2_IMAGE_INCLUDE_DIRS})
-
-link_directories(${SDL2_LIBRARY_DIRS} ${SDL2_IMAGE_LIBRARY_DIRS})
+link_directories(
+   ${SDL2_LIBRARY_DIRS}
+   ${SDL2_IMAGE_LIBRARY_DIRS}
+   ${IMAGEQUANT_LIBRARY_DIRS}
+)
 
 add_executable(vpxds
    main.cpp
    VPXDisplayServer.h
    VPXDisplayServer.cpp
    inc/mongoose/mongoose.c
    inc/mongoose/mongoose.h
+   inc/lodepng/lodepng.cpp
+   inc/lodepng/lodepng.h
 )
 
-target_link_libraries(vpxds ${SDL2_LIBRARIES} ${SDL2_IMAGE_LIBRARIES} ${X11_LIBRARIES})
-
+target_link_libraries(vpxds
+   ${SDL2_LIBRARIES}
+   ${SDL2_IMAGE_LIBRARIES}
+   ${X11_LIBRARIES}
+   libimagequant.a
+   OpenMP::OpenMP_CXX
+)
 
 add_custom_command(TARGET vpxds POST_BUILD
    COMMAND "${CMAKE_COMMAND}" -E copy_directory "${CMAKE_SOURCE_DIR}/assets" "$<TARGET_FILE_DIR:vpxds>/assets"
-)
+)

VPXDisplayServer.cpp

@@ -5,12 +5,15 @@
 #include "inc/mongoose/mongoose.h"
 #include "inc/mINI/ini.h"
 #include "inc/subprocess/subprocess.h"
+#include "inc/lodepng/lodepng.h"
 
 #include <iostream>
 #include <filesystem>
 #include <algorithm>
 #include <X11/Xlib.h>
 
+#include <libimagequant.h>
+
 static VPXDisplayServer* g_pServer = NULL;
 
 void VPXDisplayServer::Forward(struct mg_http_message *hm, struct mg_connection *c)
@@ -234,7 +237,7 @@ void VPXDisplayServer::Capture(struct mg_connection *c, void *ev_data)
       int process_return;
       if (!subprocess_join(&subprocess, &process_return)) {
          PLOGI.printf("process return: %d", process_return);
-         if (!process_return) {
+         if (!process_return && ProcessPNG(szCapture)) {
             mg_http_reply(c, 200, "", "");
             return;
          }
@@ -281,9 +284,9 @@ void VPXDisplayServer::CaptureES(struct mg_connection *c, void *ev_data)
          int process_return;
          if (!subprocess_join(&subprocess, &process_return)) {
             PLOGI.printf("process returned: %d", process_return);
-            if (!process_return) {
+            if (!process_return && ProcessPNG(szPath)) {
                struct mg_http_serve_opts opts = {};
-               mg_http_serve_file(c, hm, szPath.c_str(), &opts);
+               mg_http_serve_file(c, hm, szPath.c_str(), &opts);               
                return;
             }
          }
@@ -454,6 +457,63 @@ void VPXDisplayServer::LoadINI()
    }
 }
 
+bool VPXDisplayServer::ProcessPNG(const std::string& filename)
+{
+   unsigned int width;
+   unsigned int height;
+   unsigned char* pPixels;
+
+   if (lodepng_decode32_file(&pPixels, &width, &height, filename.c_str()))
+      return false;
+
+   liq_attr* pHandle = liq_attr_create();
+   liq_image* pImage = liq_image_create_rgba(pHandle, pPixels, width, height, 0);
+
+   liq_result* pQuantizationResult;
+   if (liq_image_quantize(pImage, pHandle, &pQuantizationResult) != LIQ_OK)
+      return false;
+
+   size_t pixelsSize = width * height;
+   unsigned char* pPixels8 = (unsigned char *)malloc(pixelsSize);
+   liq_set_dithering_level(pQuantizationResult, 1.0);
+
+   liq_write_remapped_image(pQuantizationResult, pImage, pPixels8, pixelsSize);
+   const liq_palette* pPalette = liq_get_palette(pQuantizationResult);
+
+   LodePNGState state;
+   lodepng_state_init(&state);
+   state.info_raw.colortype = LCT_PALETTE;
+   state.info_raw.bitdepth = 8;
+   state.info_png.color.colortype = LCT_PALETTE;
+   state.info_png.color.bitdepth = 8;
+
+   for (int i = 0; i < pPalette->count; i++) {
+      lodepng_palette_add(&state.info_png.color, pPalette->entries[i].r, pPalette->entries[i].g, pPalette->entries[i].b, pPalette->entries[i].a);
+      lodepng_palette_add(&state.info_raw, pPalette->entries[i].r, pPalette->entries[i].g, pPalette->entries[i].b, pPalette->entries[i].a);
+   }
+
+   unsigned char* pOutput;
+   size_t outputSize;
+   if (lodepng_encode(&pOutput, &outputSize, pPixels8, width, height, &state))
+      return false;
+
+   FILE *fp = fopen(filename.c_str(), "wb");
+   if (!fp)
+      return false;
+
+   fwrite(pOutput, 1, outputSize, fp);
+   fclose(fp);
+
+   liq_result_destroy(pQuantizationResult);
+   liq_image_destroy(pImage);
+   liq_attr_destroy(pHandle);
+
+   free(pPixels8);
+   lodepng_state_cleanup(&state);
+
+   return true;
+}
+
 int VPXDisplayServer::Start()
 {
    PLOGI << "Starting VPXDS...";

VPXDisplayServer.h

@@ -39,6 +39,7 @@ class VPXDisplayServer
    void Reset(struct mg_connection *c, void *ev_data);
    void Capture(struct mg_connection *c, void *ev_data);
    void CaptureES(struct mg_connection *c, void *ev_data);
+   bool ProcessPNG(const std::string& filename);
 
    VPXDisplay* m_pBackglassDisplay;
    VPXDisplay* m_pDMDDisplay;