Retrieves first chunk of data of remote image via HTTP GET to find out its size in pixels. PNG, JPEG

getImageSize.coffee

  getImageSize = (image, cb) ->
    fromHex = (hex) -> parseInt "0x#{hex}", 16
    req = http.request image, (res) ->
      res.setEncoding 'hex'
      res.on 'error', (e) -> cb "getImageSize error (#{image}): " + e, null, image
      res.on 'data', (chunk) ->
        m = switch res.headers['content-type']
          when 'image/jpeg'
            chunk.match 'ffc0001108(....)(....)'
          when 'image/png'
            x = chunk.match '49484452(.{8})(.{8})' # IHDR
            [null, x[2], x[1]]
        h = fromHex m?[1]
        w = fromHex m?[2]
        if h > 0 and w > 0
          cb null, [h, w], image
        else
          cb 'getImageSize: bad size(-s)', null, image
        res.destroy()
    req.on 'error', (e) -> cb "getImageSize request error (#{image}): " + e, null, image
    req.end()

Use it like

getImageSize 'http://my.remote.server/image.jpg', (error, hw, image) ->
  unless error
    console log "height: #{hw[0]}"
    console log "width: #{hw[1]}"