def metadata_chunks
      metadata.map do |key, value|
        if value.length >= METADATA_COMPRESSION_TRESHOLD
          ChunkyPNG::Chunk::CompressedText.new(key, value)
        else
          ChunkyPNG::Chunk::Text.new(key, value)
        end
      end
    end
def metadata_chunks
      metadata.map do |key, value|
        if value.length >= METADATA_COMPRESSION_TRESHOLD
          ChunkyPNG::Chunk::CompressedText.new(key, value)
        else
          ChunkyPNG::Chunk::Text.new(key, value)
        end
      end
    end
Returns the metadata for this image as PNG chunks.

 Chunks will either be of the {ChunkyPNG::Chunk::Text} type for small
 values (in bytes), or of the {ChunkyPNG::Chunk::CompressedText} type
 for values that are larger in size.

 @return [Array<ChunkyPNG::Chunk>] An array of metadata chunks.
 @see ChunkyPNG::Image::METADATA_COMPRESSION_TRESHOLD