convert-to-async

cta-callbacks.js

app.post('/process-upload', upload.single('image'), (req, res) => {
  // Start by reading the uploaded file
  fs.readFile(req.file.path, (err, originalFileBuffer) => {
    if (err) throw err;
  
    // Resize the image to 32x16, and convert to .png for consistency
    imageMagick.convert({
      srcData: originalFileBuffer,
      width: 32,
      height: 16,
      format: 'PNG'
    }, (err, smallFileBuffer) => {
      if (err) throw err;

      // Call to a utility function to get the new write-path.
      // Not important in this context, so I've excluded it.
      const newFilename = getPathForNewFile(req.file);

      // Work out the RGBA values for every pixel in the image.
      const pixels = imageMagick.getConstPixels({
        srcData: smallFileBuffer,
        x: 0,
        y: 0,
        columns: 32,
        rows: 16
      });
      
      // Save the resized .png to disk, for reference.
      fs.writeFile(newFilename, smallFileBuffer, (err, data) => {
        if (err) throw err;

        // We're done! Send the pixels to the client.
        return res.json({ done: true, pixels });

      });
    });
  });
});