Is it possible to create a GIF from input .png frames?

[GavinJoyce]

Is it possible to create a GIF from a series of .png input frames?

This example is the best that I've so far found showing how to manipulate a gif using ruby-vips. That starts with a .gif input though where my example just has a couple of .pngs.

require "vips"

frame1 = Vips::Image.new_from_file "frame1.png"
frame2 = Vips::Image.new_from_file "frame2.png"

frames = [frame1, frame2]

new_image = Vips::Image.arrayjoin(frames, across: 1)
new_image = new_image.mutate do |x|
    x.set_type! GObject::GINT_TYPE, "page-height", frame1.height * 2
end

new_image.magicksave("output.gif", format: "gif")

Perhaps unsurprisingly, this outputs a file that is a single image showing the two input frames stacked upon each other, not an animated GIF. I'm hoping that there's a way to specify things like timing between frames. I know it's possible to do this with libraries like gifsicle, but I'm hoping to do as much as possible with ruby-vips

[jcupitt]

Hi again,

You've got it, just take the *2 off. I'd write it as:

#!/usr/bin/ruby

require "vips"

frames = ARGV[1..].map do |filename| 
  Vips::Image.new_from_file filename, access: :sequential 
end

image = Vips::Image.arrayjoin frames, across: 1

image = image.mutate do |x|
    x.set_type! GObject::GINT_TYPE, "page-height", frames[0].height 
    x.set_type! Vips::ARRAY_INT_TYPE, "delay", [500, 1000]
end

image.write_to_file ARGV[0]

Then:

$ vips invert ~/pics/k2.jpg x.jpg
$ ./mkgif.rb x.gif ~/pics/k2.jpg x.jpg 

The delays are in milliseconds. You can write animated webp too, of course. There are some more controls for the GIF writer:

https://www.libvips.org/API/current/VipsForeignSave.html#vips-gifsave

[GavinJoyce]

thanks!