Mencoder

Using ImageMagick / GraphicsMagick with Mencoder

The following example Ruby program outputs a simple animation as a series of PNG pictures:

require 'RMagick'
require 'fileutils'

FileUtils::mkdir_p 'images'

# prepare font
smallText           = Magick::Draw.new
smallText.font      = 'VeraMono'
smallText.pointsize = 40
smallText.gravity   = Magick::CenterGravity

original = Magick::Image.new(300, 200) do self.background_color = "black" end

(0...25).each do |frame|

    puts "processing frame \##{frame}"

    # blur and darken last frame
    copy = original.gaussian_blur(10,8).level(0,0.7)

    # draw fresh text
    smallText.annotate(copy, 0, 0, 0, 0, "frame \#%02d" % frame) do
       self.fill = 'white'
    end

    # Save PNG:
    # * Very important! *
    # MPlayer only understands PNG images with 8 bits per channel, so the PNG's
    # must be encoded with depth=8.
    copy.write('images/image%03d.png' % frame) do self.depth = 8 end

    original = copy
end

When the program has run, create an AVI file:

mencoder mf://images/*.png -mf w=300:h=200:fps=25:type=png -ovc lavc -lavcopts vcodec=mpeg4 -o anim.avi