ImageList#montage not including most photos

Question

I have this code:

marginsBetween = 20
background = '#000000'

columns = 6
rows = 12

collage = images.montage {
  self.geometry = '+' + (marginsBetween/2).to_s + '+' + (marginsBetween/2).to_s
  self.tile = columns.to_s + 'x' + rows.to_s
  self.background_color = background
}

images is an ImageList with 96 images in it, populated as follows

images = ImageList.new()
urls.each do |url|
  images << Image.read(url)[0]
end

Where urls is just an array of image URLs

For some reason, after calling collage.flatten_image and saving that resulting image, I only have 24 photos in the grid with whitespace filling the rest. Has anyone seen this behavior before?

EDIT: It appears that this only happends with 96 images.... Any other number works fine

Answer 1

Figured it out.

Looks like in some cases, montage returns an array of images. You need to deal with it somehow.

In my case, I used resample to get the correct DPI and merge the images in one go.