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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Inference with your model\n",
    "\n",
    "In a [previous tutorial](train_your_first_model.ipynb), you successfully trained your model.\n",
    "Now, you learn how to use your model to classify a handwritten digit image. You will learn how to implement a `Translator` interface to convert between POJO and `NDArray`.\n",
    "\n",
    "\n",
    "## Preparation\n",
    "\n",
    "This tutorial requires the installation of Java Kernel. To install the Java Kernel, see the [README](https://github.com/awslabs/djl/blob/master/jupyter/README.md)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "// %mavenRepo snapshots https://oss.sonatype.org/content/repositories/snapshots/\n",
    "\n",
    "%maven ai.djl:api:0.2.1\n",
    "%maven ai.djl:repository:0.2.1\n",
    "%maven ai.djl:model-zoo:0.2.1\n",
    "%maven ai.djl.mxnet:mxnet-engine:0.2.1\n",
    "%maven ai.djl.mxnet:mxnet-model-zoo:0.2.1\n",
    "%maven org.slf4j:slf4j-api:1.7.26\n",
    "%maven org.slf4j:slf4j-simple:1.7.26\n",
    "%maven net.java.dev.jna:jna:5.3.0"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Include MXNet engine dependency\n",
    "\n",
    "This tutorial uses MXNet engine as its backend. MXNet has different [build flavor](https://mxnet.apache.org/get_started?version=v1.5.1&platform=linux&language=python&environ=pip&processor=cpu) and it is platform specific.\n",
    "Please read [here](https://github.com/awslabs/djl/blob/master/examples/README.md#engine-selection) for how to select MXNet engine flavor."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "String osName = System.getProperty(\"os.name\");\n",
    "String classifier = osName.startsWith(\"Mac\") ? \"osx-x86_64\" : osName.startsWith(\"Win\") ? \"win-x86_64\" : \"linux-x86_64\";\n",
    "\n",
    "%maven ai.djl.mxnet:mxnet-native-mkl:jar:${classifier}:1.6.0-b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import java.awt.image.*;\n",
    "import java.nio.file.*;\n",
    "import java.util.*;\n",
    "import java.util.stream.*;\n",
    "import ai.djl.*;\n",
    "import ai.djl.inference.*;\n",
    "import ai.djl.ndarray.*;\n",
    "import ai.djl.ndarray.index.*;\n",
    "import ai.djl.modality.*;\n",
    "import ai.djl.modality.cv.*;\n",
    "import ai.djl.modality.cv.util.*;\n",
    "import ai.djl.modality.cv.util.NDImageUtils.Flag;\n",
    "import ai.djl.mxnet.zoo.*;\n",
    "import ai.djl.translate.*;\n",
    "import ai.djl.util.*;\n",
    "import ai.djl.zoo.cv.classification.*;"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Step 1: Load your handwritten digit image"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "var img = BufferedImageUtils.fromUrl(\"https://djl-ai.s3.amazonaws.com/resources/images/0.png\");\n",
    "img"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Step 2: Load your model"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "Path modelDir = Paths.get(\"build/mlp\");\n",
    "Model model = Model.newInstance();\n",
    "model.setBlock(new Mlp(28, 28));\n",
    "model.load(modelDir);"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Step 3: Create a `Translator`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "Translator<BufferedImage, Classifications> translator = new Translator<BufferedImage, Classifications>() {\n",
    "\n",
    "    @Override\n",
    "    public NDList processInput(TranslatorContext ctx, BufferedImage input) {\n",
    "        // Convert BufferedImage to NDArray\n",
    "        NDArray array = BufferedImageUtils.toNDArray(ctx.getNDManager(), input, NDImageUtils.Flag.GRAYSCALE);\n",
    "        return new NDList(NDImageUtils.toTensor(array));\n",
    "    }\n",
    "\n",
    "    @Override\n",
    "    public Classifications processOutput(TranslatorContext ctx, NDList list) {\n",
    "        NDArray probabilities = list.singletonOrThrow().softmax(0);\n",
    "        List<String> indices = IntStream.range(0, 10).mapToObj(String::valueOf).collect(Collectors.toList());\n",
    "        return new Classifications(indices, probabilities);\n",
    "    }\n",
    "};\n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Step 3: Run inference"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "var predictor = model.newPredictor(translator);\n",
    "var classifications = predictor.predict(img);\n",
    "\n",
    "classifications"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Summary\n",
    "\n",
    "\n",
    "You can find the full source in the [examples project](https://github.com/awslabs/djl/blob/master/examples/docs/image_classification.md)."
   ]
  }
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