Properly split encoder and decoder

codecs/webp_enc/.gitignore

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+/*.wasm
+/*.js

codecs/webp_enc/package.json

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+{
+  "name": "webp_enc",
+  "scripts": {
+    "install": "napa",
+    "build": "docker run --rm -v $(pwd):/src trzeci/emscripten emcc -O3 -s WASM=1 -s EXTRA_EXPORTED_RUNTIME_METHODS='[\"cwrap\"]' -s ALLOW_MEMORY_GROWTH=1 -s MODULARIZE=1 -s 'EXPORT_NAME=\"webp_enc\"' -I node_modules/libwebp -o ./webp_enc.js webp_enc.c node_modules/libwebp/src/{dec,dsp,demux,enc,mux,utils}/*.c"
+  },
+  "napa": {
+    "libwebp": "webmproject/libwebp#v0.6.1"
+  },
+  "devDependencies": {
+    "napa": "^3.0.0"
+  }
+}

codecs/webp_enc/webp_enc.c

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+#include "emscripten.h"
+#include "src/webp/encode.h"
+#include <stdlib.h>
+
+EMSCRIPTEN_KEEPALIVE
+int version() {
+  return WebPGetEncoderVersion();
+}
+
+EMSCRIPTEN_KEEPALIVE
+uint8_t* create_buffer(int width, int height) {
+  return malloc(width * height * 4 * sizeof(uint8_t));
+}
+
+EMSCRIPTEN_KEEPALIVE
+void destroy_buffer(uint8_t* p) {
+  free(p);
+}
+
+int result[2];
+EMSCRIPTEN_KEEPALIVE
+void encode(uint8_t* img_in, int width, int height, float quality) {
+  uint8_t* img_out;
+  size_t size;
+  size = WebPEncodeRGBA(img_in, width, height, width * 4, quality, &img_out);
+  result[0] = (int)img_out;
+  result[1] = size;
+}
+
+EMSCRIPTEN_KEEPALIVE
+void free_result(uint8_t* result) {
+  WebPFree(result);
+}
+
+EMSCRIPTEN_KEEPALIVE
+int get_result_pointer() {
+  return result[0];
+}
+
+EMSCRIPTEN_KEEPALIVE
+int get_result_size() {
+  return result[1];
+}
+