rmagick is there a way to convert image in memory

Question

From Rmagick guide:

Converting an image to another format

Converting an image to another format is as simple as writing the image to a file.

Answer 1

# assuming you have an image
# img = Magick::Image.new( 100, 100 )
img = Magick::Image.from_blob( img.to_blob { self.format = "png" } )

Source: RMagick Docs

Here's an example on how to give it to the user

image.format = "png"
send_data image.to_blob,
    :filename => "woohoo.png",
    :disposition => 'inline',
    :quality => 90,
    :type => 'image/png'