Tiling an image over a page with ImageMagick with print margins? - pdf

Question

I am trying to get ImageMagick to do something for me and I am running into a few problems. First, I am not understanding units of measure and such passed into ImageMagick and so my script is not producing what I need. Second, the way I am doing it is extremely inefficient. Running this script takes a very long time (the one you see below is slightly trimmed down from what I am running).
So to what I am doing... I have a number of svg files with icons in them. I am looking to generate a page for each of these files. The page generated will contain the icon tiled over the entire page with a margin on the side. I am looking for 1/2 inch tiles with 1/2 margins around the page which needs to be a US Letter (8 1/2 x 11 inch).
After reading a lot of the documentation this is what I came up with.
colors=(red blue purple yellow green black)
mkdir -p generated/icons/
for color in ${colors[#]}; do
images=`printf "source/icons/${color}.svg%.0s " {1..300}`
montage $images -tile 15x20 -page Letter+1+1 -units PixelsPerInch -density 2550x3300 \
generated/icons/${color}.pdf
done
So for each of my files I run montage. I use printf to repeat the image file name 300 times. I then tile this 15x20 times. 15x20 comes from 8.5 minus 1 inch margins = 7.5*2 = 15 and likewise (11-1)*2 = 20. 300 images come from 15*20. I then say I want this on a letter page offset 1x1. (This was my attempt at a margin) I say I am speaking in pixel per inch (but none of the units seem to match up). I set the dpi to 300 by the density command where 8.5*300 = 2550 and 11*300 = 3300.
I've been toying with other settings (geometry etc.) but none of these are working. And the units don't seem to make sense either... Right now my resultant pdf is a square etc...
How do I make tiled pages as such? Also is there a way for me to do this more efficiently? What I have thus far is very slow.
EDIT:
Some more information:
i:montage --version
Version: ImageMagick 6.8.8-10 Q16 x86_64 2015-03-10 http://www.imagemagick.org
tile image:
my current output:
Notice margins not right, is square not a letter page, also tiles as skewed

Answer 1

Given the PNG image you provided, and I presume you want a 1 inch border of white all around inside an 8.5x11 inch printed image. Thus the tiled width would be 7.5 inches and tiled height would be 10 inches.
1 in = 300 dpi so border thickness = 300 px = 2 tiles thick
11-1 = 10 inches tall for tiled region height = 10*300 = 3000 px
8.5-1 = 7.5 inches wide for tiled region width = 7.5*300 = 2250 px
1 tile = 0.5 inches at 300 dpi = 0.5*300 = 150 px
convert lUDbK.png -resize "150x150!" -write mpr:tile +delete -size 2250x3000 tile:mpr:tile -bordercolor white -border 300 -units pixelsperinch -density 300 tiled_page.png
Time to process was 1.75 sec on my Mac Mini.
This produces an image which is rather large. You will have to extract the image to see the border, since this page background is white.
(Note that PNG only supports pixelspercentimeter, but IM converts my specification of pixelperinch accordingly. So if you look at the meta data, it will probably show you some other density in units of pixelspercentimeter. But they will correspond to the desired 300 dpi.)