Add gif -> webp encoder (#27)

SessionHero01 · web-flow · commit 5a1dd533c513 · 2025-10-30T13:38:06.000+11:00
diff --git a/library/src/androidTest/kotlin/network/loki/messenger/libsession_util/image/WebUtilsTest.kt b/library/src/androidTest/kotlin/network/loki/messenger/libsession_util/image/WebUtilsTest.kt
@@ -0,0 +1,69 @@
+package network.loki.messenger.libsession_util.image
+
+import android.graphics.ImageDecoder
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.sessionfoundation.libsession_util.test.R
+
+@RunWith(AndroidJUnit4::class)
+class WebUtilsTest {
+    @Test
+    fun testReencodeWebP() {
+
+        for (outputSize in listOf(200, 400, 600)) {
+            val output = InstrumentationRegistry.getInstrumentation()
+                .targetContext
+                .applicationContext
+                .resources
+                .openRawResource(R.raw.webp_animated).use { input ->
+                    WebPUtils.reencodeWebPAnimation(
+                        input = input.readAllBytes(),
+                        timeoutMills = 100_000L,
+                        targetWidth = outputSize,
+                        targetHeight = outputSize
+                    )
+                }
+
+            ImageDecoder.decodeDrawable(
+                ImageDecoder.createSource(output)
+            ) { decoder, info, source ->
+                assertEquals(outputSize, info.size.width)
+                assertEquals(outputSize, info.size.height)
+                assertTrue(info.isAnimated)
+                assertEquals("image/webp", info.mimeType)
+            }
+        }
+    }
+
+    @Test
+    fun testEncodeGIFToWebP() {
+        for (outputSize in listOf(200, 400, 600)) {
+            val output = InstrumentationRegistry.getInstrumentation()
+                .targetContext
+                .applicationContext
+                .resources
+                .openRawResource(R.raw.earth).use { input ->
+                    WebPUtils.encodeGifToWebP(
+                        input = input,
+                        timeoutMills = 100_000L,
+                        targetWidth = outputSize,
+                        targetHeight = outputSize
+                    )
+                }
+
+            ImageDecoder.decodeDrawable(
+                ImageDecoder.createSource(output)
+            ) { decoder, info, source ->
+                assertEquals("image/webp", info.mimeType)
+                assertEquals(outputSize, info.size.width)
+                assertEquals(outputSize, info.size.height)
+                assertTrue(info.isAnimated)
+            }
+        }
+    }
+}
diff --git a/library/src/androidTest/res/raw/webp_animated.webp b/library/src/androidTest/res/raw/webp_animated.webp
diff --git a/library/src/main/cpp/gif_utils.cpp b/library/src/main/cpp/gif_utils.cpp
@@ -26,7 +26,8 @@ Java_network_loki_messenger_libsession_1util_image_GifUtils_reencodeGif(JNIEnv *
         JniInputStream input_stream(env, input);
 
         EasyGifReader decoder = EasyGifReader::openCustom([](void *out_buffer, size_t size, void *ctx) {
-            return reinterpret_cast<JniInputStream*>(ctx)->read(reinterpret_cast<uint8_t *>(out_buffer), size);
+            reinterpret_cast<JniInputStream*>(ctx)->read_fully(reinterpret_cast<uint8_t *>(out_buffer), size);
+            return size;
         }, &input_stream);
 
         std::vector<uint8_t> output_buffer;
@@ -100,7 +101,7 @@ Java_network_loki_messenger_libsession_1util_image_GifUtils_reencodeGif(JNIEnv *
                         libyuv::kFilterBox
                 );
 
-                // Convert the scaled ARGB32 back to RGB24 for encoding
+                // Convert the scaled ARGB32 back to RGBA for encoding
                 libyuv::ARGBToRGBA(
                         encode_argb_buffer.data(), target_width * 4,
                         encode_rgba_buffer.data(), target_width * 4,
@@ -139,12 +140,12 @@ Java_network_loki_messenger_libsession_1util_image_GifUtils_isAnimatedGif(JNIEnv
 
             EasyGifReader decoder = EasyGifReader::openCustom(
                     [](void *out_buffer, size_t size, void *ctx) {
-                        return reinterpret_cast<JniInputStream *>(ctx)->read(
-                                reinterpret_cast<uint8_t *>(out_buffer), size);
+                        reinterpret_cast<JniInputStream*>(ctx)->read_fully(reinterpret_cast<uint8_t *>(out_buffer), size);
+                        return size;
                     }, &input_stream);
 
             return decoder.frameCount() > 1;
-        } catch (...) {
+        } catch (const EasyGifReader::Error &e) {
             // Is there's a java exception pending?
             if (env->ExceptionCheck()) {
                 return false;
diff --git a/library/src/main/cpp/jni_input_stream.h b/library/src/main/cpp/jni_input_stream.h
@@ -32,6 +32,17 @@ class JniInputStream {
 
         return bytes_read;
     }
+
+    void read_fully(uint8_t *buffer, size_t size) {
+        size_t total_bytes_read = 0;
+        while (total_bytes_read < size) {
+            size_t bytes_read = read(buffer + total_bytes_read, size - total_bytes_read);
+            if (bytes_read == 0) {
+                throw std::runtime_error("EOF reached");
+            }
+            total_bytes_read += bytes_read;
+        }
+    }
 };
 
 #endif //LIBSESSION_UTIL_ANDROID_JNI_INPUT_STREAM_H
diff --git a/library/src/main/cpp/webp_utils.cpp b/library/src/main/cpp/webp_utils.cpp
@@ -1,5 +1,6 @@
 #include <jni.h>
 #include "jni_utils.h"
+#include "jni_input_stream.h"
 
 #include <chrono>
 
@@ -8,6 +9,8 @@
 #include <webp/decode.h>
 #include <webp/encode.h>
 
+#include <EasyGifReader.h>
+
 
 template<typename T>
 using WebPPtr = std::unique_ptr<T, void (*)(T *)>;
@@ -123,3 +126,106 @@ Java_network_loki_messenger_libsession_1util_image_WebPUtils_reencodeWebPAnimati
 
     return out_ref.java_array();
 }
+
+
+static void destroyWebPPicture(WebPPicture* pic) {
+    WebPPictureFree(pic);
+    delete pic;
+}
+
+extern "C"
+JNIEXPORT jbyteArray JNICALL
+Java_network_loki_messenger_libsession_1util_image_WebPUtils_encodeGifToWebP(JNIEnv *env,
+                                                                             jobject thiz,
+                                                                             jobject input,
+                                                                             jlong timeout_mills,
+                                                                             jint target_width,
+                                                                             jint target_height) {
+    return jni_utils::run_catching_cxx_exception_or_throws<jbyteArray>(env, [=]() -> jbyteArray {
+        JniInputStream input_stream(env, input);
+
+        const auto deadline = std::chrono::high_resolution_clock::now() + std::chrono::milliseconds(timeout_mills);
+
+        auto is_timeout = [&]() {
+            if (std::chrono::high_resolution_clock::now() > deadline) {
+                env->ThrowNew(env->FindClass("java/util/concurrent/TimeoutException"),
+                              "GIF re-encoding timed out");
+                return true;
+            }
+            return false;
+        };
+
+        EasyGifReader decoder = EasyGifReader::openCustom([](void *out_buffer, size_t size, void *ctx) {
+            reinterpret_cast<JniInputStream*>(ctx)->read_fully(reinterpret_cast<uint8_t *>(out_buffer), size);
+            return size;
+        }, &input_stream);
+
+        WebPPtr<WebPAnimEncoder> encoder(WebPAnimEncoderNew(target_width, target_height, nullptr), &WebPAnimEncoderDelete);
+        if (!encoder) {
+            env->ThrowNew(env->FindClass("java/lang/RuntimeException"),
+                          "Failed to create animation encoder");
+            return 0;
+        }
+
+        std::vector<uint8_t> decode_argb_buffer(decoder.width() * decoder.height() * 4);
+        std::vector<uint8_t> encode_argb_buffer;
+        int frame_delay_ms = 0;
+
+        WebPPtr<WebPPicture> pic(new WebPPicture, &destroyWebPPicture);
+        WebPPictureInit(pic.get());
+        pic->use_argb = 1;
+
+        for (auto frame = decoder.begin(); frame != decoder.end() && !is_timeout(); ++frame) {
+            // Import the frame into a WebPPicture
+            pic->width = decoder.width();
+            pic->height = decoder.height();
+            pic->argb_stride = decoder.width();
+
+            if (!WebPPictureImportRGBA(pic.get(), frame->pixels(), decoder.width() * 4)) {
+                env->ThrowNew(env->FindClass("java/lang/RuntimeException"),
+                              "Failed to import frame into picture");
+                return nullptr;
+            }
+
+            // If the target size is different, rescale the frame
+            if (target_width != decoder.width() || target_height != decoder.height()) {
+                if (!WebPPictureRescale(pic.get(), target_width, target_height)) {
+                    env->ThrowNew(env->FindClass("java/lang/RuntimeException"),
+                                  "Failed to rescale picture");
+                    return nullptr;
+                }
+            }
+
+            // Now we have a WebPPicture ready to be added to the encoder
+            WebPConfig encode_config;
+            WebPConfigInit(&encode_config);
+            encode_config.quality = 95.f;
+
+            frame_delay_ms += frame.duration().milliseconds();
+
+            auto encode_succeeded = WebPAnimEncoderAdd(encoder.get(), pic.get(),
+                                                       frame_delay_ms, &encode_config);
+
+            if (!encode_succeeded) {
+                env->ThrowNew(env->FindClass("java/lang/RuntimeException"),
+                              WebPAnimEncoderGetError(encoder.get()));
+                return nullptr;
+            }
+        }
+
+        WebPData out;
+        WebPDataInit(&out);
+
+        if (!WebPAnimEncoderAssemble(encoder.get(), &out)) {
+            env->ThrowNew(env->FindClass("java/lang/RuntimeException"),
+                          "Failed to assemble animation");
+            return nullptr;
+        }
+
+        jni_utils::JavaByteArrayRef out_ref(env, env->NewByteArray(out.size));
+        std::memcpy(out_ref.bytes(), out.bytes, out.size);
+        WebPDataClear(&out);
+
+        return out_ref.java_array();
+    });
+}
diff --git a/library/src/main/java/network/loki/messenger/libsession_util/image/WebPUtils.kt b/library/src/main/java/network/loki/messenger/libsession_util/image/WebPUtils.kt
@@ -1,6 +1,9 @@
 package network.loki.messenger.libsession_util.image
 
-object WebPUtils {
+import network.loki.messenger.libsession_util.LibSessionUtilCApi
+import java.io.InputStream
+
+object WebPUtils : LibSessionUtilCApi() {
     /**
      * Re-encode the webP animation, resizing each frame to scale to the target width and height.
      * This can serve two purposes:
@@ -18,4 +21,11 @@ object WebPUtils {
         targetWidth: Int,
         targetHeight: Int,
     ): ByteArray
+
+    external fun encodeGifToWebP(
+        input: InputStream,
+        timeoutMills: Long,
+        targetWidth: Int,
+        targetHeight: Int,
+    ): ByteArray
 }
