image-example.cc

// -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
//
// Example how to display an image, including animated images using
// ImageMagick. For a full utility that does a few more things, have a look
// at the led-image-viewer in ../utils
//
// Showing an image is not so complicated, essentially just copy all the
// pixels to the canvas. How to get the pixels ? In this example we're using
// the graphicsmagick library as universal image loader library that
// can also deal with animated images.
// You can of course do your own image loading or use some other library.
//
// This requires an external dependency, so install these first before you
// can call `make image-example`
//   sudo apt-get update
//   sudo apt-get install libgraphicsmagick++-dev libwebp-dev -y
//   make image-example

#include "led-matrix.h"

#include <math.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>

#include <exception>
#include <Magick++.h>
#include <magick/image.h>

using rgb_matrix::Canvas;
using rgb_matrix::RGBMatrix;
using rgb_matrix::FrameCanvas;

// Make sure we can exit gracefully when Ctrl-C is pressed.
volatile bool interrupt_received = false;
static void InterruptHandler(int signo) {
  interrupt_received = true;
}

using ImageVector = std::vector<Magick::Image>;

// Given the filename, load the image and scale to the size of the
// matrix.
// // If this is an animated image, the resutlting vector will contain multiple.
static ImageVector LoadImageAndScaleImage(const char *filename,
                                          int target_width,
                                          int target_height) {
  ImageVector result;

  ImageVector frames;
  try {
    readImages(&frames, filename);
  } catch (std::exception &e) {
    if (e.what())
      fprintf(stderr, "%s\n", e.what());
    return result;
  }

  if (frames.empty()) {
    fprintf(stderr, "No image found.");
    return result;
  }

  // Animated images have partial frames that need to be put together
  if (frames.size() > 1) {
    Magick::coalesceImages(&result, frames.begin(), frames.end());
  } else {
    result.push_back(frames[0]); // just a single still image.
  }

  for (Magick::Image &image : result) {
    image.scale(Magick::Geometry(target_width, target_height));
  }

  return result;
}


// Copy an image to a Canvas. Note, the RGBMatrix is implementing the Canvas
// interface as well as the FrameCanvas we use in the double-buffering of the
// animted image.
void CopyImageToCanvas(const Magick::Image &image, Canvas *canvas) {
  const int offset_x = 0, offset_y = 0;  // If you want to move the image.
  // Copy all the pixels to the canvas.
  for (size_t y = 0; y < image.rows(); ++y) {
    for (size_t x = 0; x < image.columns(); ++x) {
      const Magick::Color &c = image.pixelColor(x, y);
      if (c.alphaQuantum() < 256) {
        canvas->SetPixel(x + offset_x, y + offset_y,
                         ScaleQuantumToChar(c.redQuantum()),
                         ScaleQuantumToChar(c.greenQuantum()),
                         ScaleQuantumToChar(c.blueQuantum()));
      }
    }
  }
}

// An animated image has to constantly swap to the next frame.
// We're using double-buffering and fill an offscreen buffer first, then show.
void ShowAnimatedImage(const ImageVector &images, RGBMatrix *matrix) {
  FrameCanvas *offscreen_canvas = matrix->CreateFrameCanvas();
  while (!interrupt_received) {
    for (const auto &image : images) {
      if (interrupt_received) break;
      CopyImageToCanvas(image, offscreen_canvas);
      offscreen_canvas = matrix->SwapOnVSync(offscreen_canvas);
      usleep(image.animationDelay() * 10000);  // 1/100s converted to usec
    }
  }
}

int usage(const char *progname) {
  fprintf(stderr, "Usage: %s [led-matrix-options] <image-filename>\n",
          progname);
  rgb_matrix::PrintMatrixFlags(stderr);
  return 1;
}

int main(int argc, char *argv[]) {
  Magick::InitializeMagick(*argv);

  // Initialize the RGB matrix with
  RGBMatrix::Options matrix_options;
  rgb_matrix::RuntimeOptions runtime_opt;
  if (!rgb_matrix::ParseOptionsFromFlags(&argc, &argv,
                                         &matrix_options, &runtime_opt)) {
    return usage(argv[0]);
  }

  if (argc != 2)
    return usage(argv[0]);
  const char *filename = argv[1];

  signal(SIGTERM, InterruptHandler);
  signal(SIGINT, InterruptHandler);

  RGBMatrix *matrix = RGBMatrix::CreateFromOptions(matrix_options, runtime_opt);
  if (matrix == NULL)
    return 1;

  ImageVector images = LoadImageAndScaleImage(filename,
                                              matrix->width(),
                                              matrix->height());
  switch (images.size()) {
  case 0:   // failed to load image.
    break;
  case 1:   // Simple example: one image to show
    CopyImageToCanvas(images[0], matrix);
    while (!interrupt_received) sleep(1000);  // Until Ctrl-C is pressed
    break;
  default:  // More than one image: this is an animation.
    ShowAnimatedImage(images, matrix);
    break;
  }

  matrix->Clear();
  delete matrix;

  return 0;
}