Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
See -swap at http://www.imagemagick.org/Usage/basics/#swap. You can also just list your images in the order you want them appended. There is no need for -size 500x500. The output of append will be as large as needed to hold your images.
See http://www.imagemagick.org/Usage/layers/#append. Append just puts the images together. It has no size control. Any mismatched sizes will be filled with background color. If you want to put images in special places in a 500x500 background image, then you need either -compose over -composite (pair-wise) or -page ... -flatten. See http://www.imagemagick.org/Usage/layers/#flatten
Not that I know of; but there was a thread about it a couple of years ago. I tried it out with php and an external library but I have formatted my PC since then and no longer have the code.
As far as I can remember:
1/ Send the image from the webpage to php via Ajax and base64
2/ Save a temporary file for the next stage. If you can remember back a few years I was having a problem with base64 and so I had to do this step with GD as I could not get IM to work. If I could have got the base64 to work I could probably have avoided the temporary image.
3/ Cropped out all the heads with IM and saved each one.
4/ Draw a red square outline around each head with IM, resize and save.
It worked quite well on my sample images but I did not take it any further. The main idea was to generate a webpage with the main image and heads outlined then a list of heads with a space next to it. I was then going to supply links to relatives and they could then use an online form to fill in the missing names or supply alternative names if they thought any were incorrect.