screenshot.cpp

/*
* Vulkan Example - Taking screenshots
*
* Copyright (C) 2016 by Sascha Willems - www.saschawillems.de
*
* This code is licensed under the MIT license (MIT)
* (http://opensource.org/licenses/MIT)
*/

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vector>

#define GLM_FORCE_RADIANS
#define GLM_FORCE_DEPTH_ZERO_TO_ONE
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>

#include "VulkanModel.hpp"
#include "vulkanexamplebase.h"
#include <vulkan/vulkan.h>

#define ENABLE_VALIDATION false

class VulkanExample : public VulkanExampleBase {
public:
  // Vertex layout for the models
  vks::VertexLayout vertexLayout = vks::VertexLayout({
      vks::VERTEX_COMPONENT_POSITION, vks::VERTEX_COMPONENT_NORMAL,
      vks::VERTEX_COMPONENT_COLOR,
  });

  vks::Model model;
  vks::Buffer uniformBuffer;

  struct {
    glm::mat4 projection;
    glm::mat4 model;
    glm::mat4 view;
    int32_t texIndex = 0;
  } uboVS;

  VkPipelineLayout pipelineLayout;
  VkPipeline pipeline;
  VkDescriptorSetLayout descriptorSetLayout;
  VkDescriptorSet descriptorSet;

  bool screenshotSaved = false;

  VulkanExample() : VulkanExampleBase(ENABLE_VALIDATION) {
    title = "Saving framebuffer to screenshot";
    settings.overlay = true;

    camera.type = Camera::CameraType::lookat;
    camera.setPerspective(60.0f, (float)width / (float)height, 0.1f, 512.0f);
    camera.setRotation(glm::vec3(-25.0f, 23.75f, 0.0f));
    camera.setTranslation(glm::vec3(0.0f, 0.0f, -2.0f));
  }

  ~VulkanExample() {
    vkDestroyPipeline(device, pipeline, nullptr);
    vkDestroyPipelineLayout(device, pipelineLayout, nullptr);
    vkDestroyDescriptorSetLayout(device, descriptorSetLayout, nullptr);
    model.destroy();
    uniformBuffer.destroy();
  }

  void loadAssets() {
    model.loadFromFile(getAssetPath() + "models/chinesedragon.dae",
                       vertexLayout, 0.1f, vulkanDevice, queue);
  }

  void buildCommandBuffers() {
    VkCommandBufferBeginInfo cmdBufInfo =
        vks::initializers::commandBufferBeginInfo();

    VkClearValue clearValues[2];
    clearValues[0].color = defaultClearColor;
    clearValues[1].depthStencil = {1.0f, 0};

    VkRenderPassBeginInfo renderPassBeginInfo =
        vks::initializers::renderPassBeginInfo();
    renderPassBeginInfo.renderPass = renderPass;
    renderPassBeginInfo.renderArea.offset.x = 0;
    renderPassBeginInfo.renderArea.offset.y = 0;
    renderPassBeginInfo.renderArea.extent.width = width;
    renderPassBeginInfo.renderArea.extent.height = height;
    renderPassBeginInfo.clearValueCount = 2;
    renderPassBeginInfo.pClearValues = clearValues;

    for (int32_t i = 0; i < drawCmdBuffers.size(); ++i) {
      // Set target frame buffer
      renderPassBeginInfo.framebuffer = frameBuffers[i];

      VK_CHECK_RESULT(vkBeginCommandBuffer(drawCmdBuffers[i], &cmdBufInfo));

      vkCmdBeginRenderPass(drawCmdBuffers[i], &renderPassBeginInfo,
                           VK_SUBPASS_CONTENTS_INLINE);

      VkViewport viewport =
          vks::initializers::viewport((float)width, (float)height, 0.0f, 1.0f);
      vkCmdSetViewport(drawCmdBuffers[i], 0, 1, &viewport);

      VkRect2D scissor = vks::initializers::rect2D(width, height, 0, 0);
      vkCmdSetScissor(drawCmdBuffers[i], 0, 1, &scissor);

      vkCmdBindDescriptorSets(drawCmdBuffers[i],
                              VK_PIPELINE_BIND_POINT_GRAPHICS, pipelineLayout,
                              0, 1, &descriptorSet, 0, NULL);
      vkCmdBindPipeline(drawCmdBuffers[i], VK_PIPELINE_BIND_POINT_GRAPHICS,
                        pipeline);

      VkDeviceSize offsets[1] = {0};
      vkCmdBindVertexBuffers(drawCmdBuffers[i], 0, 1, &model.vertices.buffer,
                             offsets);
      vkCmdBindIndexBuffer(drawCmdBuffers[i], model.indices.buffer, 0,
                           VK_INDEX_TYPE_UINT32);

      vkCmdDrawIndexed(drawCmdBuffers[i], model.indexCount, 1, 0, 0, 0);

      vkCmdEndRenderPass(drawCmdBuffers[i]);

      VK_CHECK_RESULT(vkEndCommandBuffer(drawCmdBuffers[i]));
    }
  }

  void setupDescriptorPool() {
    std::vector<VkDescriptorPoolSize> poolSizes = {
        vks::initializers::descriptorPoolSize(VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER,
                                              1),
    };
    VkDescriptorPoolCreateInfo descriptorPoolInfo =
        vks::initializers::descriptorPoolCreateInfo(poolSizes, 2);
    VK_CHECK_RESULT(vkCreateDescriptorPool(device, &descriptorPoolInfo, nullptr,
                                           &descriptorPool));
  }

  void setupDescriptorSetLayout() {
    std::vector<VkDescriptorSetLayoutBinding> setLayoutBindings = {
        vks::initializers::descriptorSetLayoutBinding(
            VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, VK_SHADER_STAGE_VERTEX_BIT,
            0), // Binding 0: Vertex shader uniform buffer
    };
    VkDescriptorSetLayoutCreateInfo descriptorLayout =
        vks::initializers::descriptorSetLayoutCreateInfo(setLayoutBindings);
    VK_CHECK_RESULT(vkCreateDescriptorSetLayout(device, &descriptorLayout,
                                                nullptr, &descriptorSetLayout));

    VkPipelineLayoutCreateInfo pPipelineLayoutCreateInfo =
        vks::initializers::pipelineLayoutCreateInfo(&descriptorSetLayout, 1);
    VK_CHECK_RESULT(vkCreatePipelineLayout(device, &pPipelineLayoutCreateInfo,
                                           nullptr, &pipelineLayout));
  }

  void setupDescriptorSet() {
    VkDescriptorSetAllocateInfo allocInfo =
        vks::initializers::descriptorSetAllocateInfo(descriptorPool,
                                                     &descriptorSetLayout, 1);
    VK_CHECK_RESULT(
        vkAllocateDescriptorSets(device, &allocInfo, &descriptorSet));
    std::vector<VkWriteDescriptorSet> writeDescriptorSets = {
        vks::initializers::writeDescriptorSet(
            descriptorSet, VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, 0,
            &uniformBuffer
                 .descriptor), // Binding 0: Vertex shader uniform buffer
    };
    vkUpdateDescriptorSets(device, writeDescriptorSets.size(),
                           writeDescriptorSets.data(), 0, nullptr);
  }

  void preparePipelines() {
    VkPipelineInputAssemblyStateCreateInfo inputAssemblyState =
        vks::initializers::pipelineInputAssemblyStateCreateInfo(
            VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST, 0, VK_FALSE);
    VkPipelineRasterizationStateCreateInfo rasterizationState =
        vks::initializers::pipelineRasterizationStateCreateInfo(
            VK_POLYGON_MODE_FILL, VK_CULL_MODE_BACK_BIT,
            VK_FRONT_FACE_CLOCKWISE, 0);
    VkPipelineColorBlendAttachmentState blendAttachmentState =
        vks::initializers::pipelineColorBlendAttachmentState(0xf, VK_FALSE);
    VkPipelineColorBlendStateCreateInfo colorBlendState =
        vks::initializers::pipelineColorBlendStateCreateInfo(
            1, &blendAttachmentState);
    VkPipelineDepthStencilStateCreateInfo depthStencilState =
        vks::initializers::pipelineDepthStencilStateCreateInfo(
            VK_TRUE, VK_TRUE, VK_COMPARE_OP_LESS_OR_EQUAL);
    VkPipelineViewportStateCreateInfo viewportState =
        vks::initializers::pipelineViewportStateCreateInfo(1, 1, 0);
    VkPipelineMultisampleStateCreateInfo multisampleState =
        vks::initializers::pipelineMultisampleStateCreateInfo(
            VK_SAMPLE_COUNT_1_BIT, 0);
    std::vector<VkDynamicState> dynamicStateEnables = {
        VK_DYNAMIC_STATE_VIEWPORT, VK_DYNAMIC_STATE_SCISSOR};
    VkPipelineDynamicStateCreateInfo dynamicState =
        vks::initializers::pipelineDynamicStateCreateInfo(dynamicStateEnables);

    // Vertex bindings and attributes
    // Binding description
    std::vector<VkVertexInputBindingDescription> vertexInputBindings = {
        vks::initializers::vertexInputBindingDescription(
            0, vertexLayout.stride(), VK_VERTEX_INPUT_RATE_VERTEX),
    };
    // Attribute descriptions
    std::vector<VkVertexInputAttributeDescription> vertexInputAttributes = {
        vks::initializers::vertexInputAttributeDescription(
            0, 0, VK_FORMAT_R32G32B32_SFLOAT, 0), // Position
        vks::initializers::vertexInputAttributeDescription(
            0, 1, VK_FORMAT_R32G32B32_SFLOAT, sizeof(float) * 3), // Normal
        vks::initializers::vertexInputAttributeDescription(
            0, 2, VK_FORMAT_R32G32B32_SFLOAT, sizeof(float) * 6), // Color
    };
    VkPipelineVertexInputStateCreateInfo vertexInputState =
        vks::initializers::pipelineVertexInputStateCreateInfo();
    vertexInputState.vertexBindingDescriptionCount =
        static_cast<uint32_t>(vertexInputBindings.size());
    vertexInputState.pVertexBindingDescriptions = vertexInputBindings.data();
    vertexInputState.vertexAttributeDescriptionCount =
        static_cast<uint32_t>(vertexInputAttributes.size());
    vertexInputState.pVertexAttributeDescriptions =
        vertexInputAttributes.data();

    std::array<VkPipelineShaderStageCreateInfo, 2> shaderStages = {
        loadShader(getAssetPath() + "shaders/screenshot/mesh.vert.spv",
                   VK_SHADER_STAGE_VERTEX_BIT),
        loadShader(getAssetPath() + "shaders/screenshot/mesh.frag.spv",
                   VK_SHADER_STAGE_FRAGMENT_BIT),
    };

    VkGraphicsPipelineCreateInfo pipelineCreateInfo =
        vks::initializers::pipelineCreateInfo(pipelineLayout, renderPass, 0);
    pipelineCreateInfo.pInputAssemblyState = &inputAssemblyState;
    pipelineCreateInfo.pRasterizationState = &rasterizationState;
    pipelineCreateInfo.pColorBlendState = &colorBlendState;
    pipelineCreateInfo.pMultisampleState = &multisampleState;
    pipelineCreateInfo.pViewportState = &viewportState;
    pipelineCreateInfo.pDepthStencilState = &depthStencilState;
    pipelineCreateInfo.pDynamicState = &dynamicState;
    pipelineCreateInfo.stageCount = shaderStages.size();
    pipelineCreateInfo.pStages = shaderStages.data();
    pipelineCreateInfo.pVertexInputState = &vertexInputState;
    VK_CHECK_RESULT(vkCreateGraphicsPipelines(
        device, pipelineCache, 1, &pipelineCreateInfo, nullptr, &pipeline));
  }

  void prepareUniformBuffers() {
    // Vertex shader uniform buffer block
    vulkanDevice->createBuffer(VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT,
                               VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
                                   VK_MEMORY_PROPERTY_HOST_COHERENT_BIT,
                               &uniformBuffer, sizeof(uboVS));
    VK_CHECK_RESULT(uniformBuffer.map());
    updateUniformBuffers();
  }

  void updateUniformBuffers() {
    uboVS.projection = camera.matrices.perspective;
    uboVS.view = camera.matrices.view;
    uboVS.model = glm::mat4(1.0f);
    uniformBuffer.copyTo(&uboVS, sizeof(uboVS));
  }

  // Take a screenshot from the current swapchain image
  // This is done using a blit from the swapchain image to a linear image whose
  // memory content is then saved as a ppm image
  // Getting the image date directly from a swapchain image wouldn't work as
  // they're usually stored in an implementation dependant optimal tiling format
  // Note: This requires the swapchain images to be created with the
  // VK_IMAGE_USAGE_TRANSFER_SRC_BIT flag (see VulkanSwapChain::create)
  void saveScreenshot(const char *filename) {
    screenshotSaved = false;
    bool supportsBlit = true;

    // Check blit support for source and destination
    VkFormatProperties formatProps;

    // Check if the device supports blitting from optimal images (the swapchain
    // images are in optimal format)
    vkGetPhysicalDeviceFormatProperties(physicalDevice, swapChain.colorFormat,
                                        &formatProps);
    if (!(formatProps.optimalTilingFeatures & VK_FORMAT_FEATURE_BLIT_SRC_BIT)) {
      std::cerr << "Device does not support blitting from optimal tiled "
                   "images, using copy instead of blit!"
                << std::endl;
      supportsBlit = false;
    }

    // Check if the device supports blitting to linear images
    vkGetPhysicalDeviceFormatProperties(physicalDevice,
                                        VK_FORMAT_R8G8B8A8_UNORM, &formatProps);
    if (!(formatProps.linearTilingFeatures & VK_FORMAT_FEATURE_BLIT_DST_BIT)) {
      std::cerr << "Device does not support blitting to linear tiled images, "
                   "using copy instead of blit!"
                << std::endl;
      supportsBlit = false;
    }

    // Source for the copy is the last rendered swapchain image
    VkImage srcImage = swapChain.images[currentBuffer];

    // Create the linear tiled destination image to copy to and to read the
    // memory from
    VkImageCreateInfo imageCreateCI(vks::initializers::imageCreateInfo());
    imageCreateCI.imageType = VK_IMAGE_TYPE_2D;
    // Note that vkCmdBlitImage (if supported) will also do format conversions
    // if the swapchain color format would differ
    imageCreateCI.format = VK_FORMAT_R8G8B8A8_UNORM;
    imageCreateCI.extent.width = width;
    imageCreateCI.extent.height = height;
    imageCreateCI.extent.depth = 1;
    imageCreateCI.arrayLayers = 1;
    imageCreateCI.mipLevels = 1;
    imageCreateCI.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
    imageCreateCI.samples = VK_SAMPLE_COUNT_1_BIT;
    imageCreateCI.tiling = VK_IMAGE_TILING_LINEAR;
    imageCreateCI.usage = VK_IMAGE_USAGE_TRANSFER_DST_BIT;
    // Create the image
    VkImage dstImage;
    VK_CHECK_RESULT(vkCreateImage(device, &imageCreateCI, nullptr, &dstImage));
    // Create memory to back up the image
    VkMemoryRequirements memRequirements;
    VkMemoryAllocateInfo memAllocInfo(vks::initializers::memoryAllocateInfo());
    VkDeviceMemory dstImageMemory;
    vkGetImageMemoryRequirements(device, dstImage, &memRequirements);
    memAllocInfo.allocationSize = memRequirements.size;
    // Memory must be host visible to copy from
    memAllocInfo.memoryTypeIndex =
        vulkanDevice->getMemoryType(memRequirements.memoryTypeBits,
                                    VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
                                        VK_MEMORY_PROPERTY_HOST_COHERENT_BIT);
    VK_CHECK_RESULT(
        vkAllocateMemory(device, &memAllocInfo, nullptr, &dstImageMemory));
    VK_CHECK_RESULT(vkBindImageMemory(device, dstImage, dstImageMemory, 0));

    // Do the actual blit from the swapchain image to our host visible
    // destination image
    VkCommandBuffer copyCmd = vulkanDevice->createCommandBuffer(
        VK_COMMAND_BUFFER_LEVEL_PRIMARY, true);

    VkImageMemoryBarrier imageMemoryBarrier =
        vks::initializers::imageMemoryBarrier();

    // Transition destination image to transfer destination layout
    vks::tools::insertImageMemoryBarrier(
        copyCmd, dstImage, 0, VK_ACCESS_TRANSFER_WRITE_BIT,
        VK_IMAGE_LAYOUT_UNDEFINED, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
        VK_PIPELINE_STAGE_TRANSFER_BIT, VK_PIPELINE_STAGE_TRANSFER_BIT,
        VkImageSubresourceRange{VK_IMAGE_ASPECT_COLOR_BIT, 0, 1, 0, 1});

    // Transition swapchain image from present to transfer source layout
    vks::tools::insertImageMemoryBarrier(
        copyCmd, srcImage, VK_ACCESS_MEMORY_READ_BIT,
        VK_ACCESS_TRANSFER_READ_BIT, VK_IMAGE_LAYOUT_PRESENT_SRC_KHR,
        VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL, VK_PIPELINE_STAGE_TRANSFER_BIT,
        VK_PIPELINE_STAGE_TRANSFER_BIT,
        VkImageSubresourceRange{VK_IMAGE_ASPECT_COLOR_BIT, 0, 1, 0, 1});

    // If source and destination support blit we'll blit as this also does
    // automatic format conversion (e.g. from BGR to RGB)
    if (supportsBlit) {
      // Define the region to blit (we will blit the whole swapchain image)
      VkOffset3D blitSize;
      blitSize.x = width;
      blitSize.y = height;
      blitSize.z = 1;
      VkImageBlit imageBlitRegion{};
      imageBlitRegion.srcSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
      imageBlitRegion.srcSubresource.layerCount = 1;
      imageBlitRegion.srcOffsets[1] = blitSize;
      imageBlitRegion.dstSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
      imageBlitRegion.dstSubresource.layerCount = 1;
      imageBlitRegion.dstOffsets[1] = blitSize;

      // Issue the blit command
      vkCmdBlitImage(copyCmd, srcImage, VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
                     dstImage, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, 1,
                     &imageBlitRegion, VK_FILTER_NEAREST);
    } else {
      // Otherwise use image copy (requires us to manually flip components)
      VkImageCopy imageCopyRegion{};
      imageCopyRegion.srcSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
      imageCopyRegion.srcSubresource.layerCount = 1;
      imageCopyRegion.dstSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
      imageCopyRegion.dstSubresource.layerCount = 1;
      imageCopyRegion.extent.width = width;
      imageCopyRegion.extent.height = height;
      imageCopyRegion.extent.depth = 1;

      // Issue the copy command
      vkCmdCopyImage(copyCmd, srcImage, VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
                     dstImage, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, 1,
                     &imageCopyRegion);
    }

    // Transition destination image to general layout, which is the required
    // layout for mapping the image memory later on
    vks::tools::insertImageMemoryBarrier(
        copyCmd, dstImage, VK_ACCESS_TRANSFER_WRITE_BIT,
        VK_ACCESS_MEMORY_READ_BIT, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL,
        VK_IMAGE_LAYOUT_GENERAL, VK_PIPELINE_STAGE_TRANSFER_BIT,
        VK_PIPELINE_STAGE_TRANSFER_BIT,
        VkImageSubresourceRange{VK_IMAGE_ASPECT_COLOR_BIT, 0, 1, 0, 1});

    // Transition back the swap chain image after the blit is done
    vks::tools::insertImageMemoryBarrier(
        copyCmd, srcImage, VK_ACCESS_TRANSFER_READ_BIT,
        VK_ACCESS_MEMORY_READ_BIT, VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
        VK_IMAGE_LAYOUT_PRESENT_SRC_KHR, VK_PIPELINE_STAGE_TRANSFER_BIT,
        VK_PIPELINE_STAGE_TRANSFER_BIT,
        VkImageSubresourceRange{VK_IMAGE_ASPECT_COLOR_BIT, 0, 1, 0, 1});

    vulkanDevice->flushCommandBuffer(copyCmd, queue);

    // Get layout of the image (including row pitch)
    VkImageSubresource subResource{VK_IMAGE_ASPECT_COLOR_BIT, 0, 0};
    VkSubresourceLayout subResourceLayout;
    vkGetImageSubresourceLayout(device, dstImage, &subResource,
                                &subResourceLayout);

    // Map image memory so we can start copying from it
    const char *data;
    vkMapMemory(device, dstImageMemory, 0, VK_WHOLE_SIZE, 0, (void **)&data);
    data += subResourceLayout.offset;

    std::ofstream file(filename, std::ios::out | std::ios::binary);

    // ppm header
    file << "P6\n" << width << "\n" << height << "\n" << 255 << "\n";

    // If source is BGR (destination is always RGB) and we can't use blit (which
    // does automatic conversion), we'll have to manually swizzle color
    // components
    bool colorSwizzle = false;
    // Check if source is BGR
    // Note: Not complete, only contains most common and basic BGR surface
    // formats for demonstation purposes
    if (!supportsBlit) {
      std::vector<VkFormat> formatsBGR = {VK_FORMAT_B8G8R8A8_SRGB,
                                          VK_FORMAT_B8G8R8A8_UNORM,
                                          VK_FORMAT_B8G8R8A8_SNORM};
      colorSwizzle = (std::find(formatsBGR.begin(), formatsBGR.end(),
                                swapChain.colorFormat) != formatsBGR.end());
    }

    // ppm binary pixel data
    for (uint32_t y = 0; y < height; y++) {
      unsigned int *row = (unsigned int *)data;
      for (uint32_t x = 0; x < width; x++) {
        if (colorSwizzle) {
          file.write((char *)row + 2, 1);
          file.write((char *)row + 1, 1);
          file.write((char *)row, 1);
        } else {
          file.write((char *)row, 3);
        }
        row++;
      }
      data += subResourceLayout.rowPitch;
    }
    file.close();

    std::cout << "Screenshot saved to disk" << std::endl;

    // Clean up resources
    vkUnmapMemory(device, dstImageMemory);
    vkFreeMemory(device, dstImageMemory, nullptr);
    vkDestroyImage(device, dstImage, nullptr);

    screenshotSaved = true;
  }

  void draw() {
    VulkanExampleBase::prepareFrame();

    submitInfo.commandBufferCount = 1;
    submitInfo.pCommandBuffers = &drawCmdBuffers[currentBuffer];
    VK_CHECK_RESULT(vkQueueSubmit(queue, 1, &submitInfo, VK_NULL_HANDLE));

    VulkanExampleBase::submitFrame();
  }

  void prepare() {
    VulkanExampleBase::prepare();
    loadAssets();
    prepareUniformBuffers();
    setupDescriptorSetLayout();
    preparePipelines();
    setupDescriptorPool();
    setupDescriptorSet();
    buildCommandBuffers();
    prepared = true;
  }

  virtual void render() {
    if (!prepared)
      return;
    draw();
  }

  virtual void viewChanged() { updateUniformBuffers(); }

  virtual void OnUpdateUIOverlay(vks::UIOverlay *overlay) {
    if (overlay->header("Functions")) {
      if (overlay->button("Take screenshot")) {
        saveScreenshot("screenshot.ppm");
      }
      if (screenshotSaved) {
        overlay->text("Screenshot saved as screenshot.ppm");
      }
    }
  }
};

VULKAN_EXAMPLE_MAIN()