i876 - Make memory, map, and disk limits in im_identify configurable

- Added environment variable support for ImageMagick memory, map, and disk limits in the `im_identify` method
- Falls back to imagemagick-6-policy.xml defaults if no configuration is provided
- Improves flexibility and control over resource usage during image processing

lib/iiif_print/image_tool.rb

@@ -74,7 +74,18 @@ def im_identify_geometry(lines)
 
     # @return [Array<String>] lines of output from imagemagick `identify`
     def im_identify
-      cmd = "identify -limit memory 8GiB -limit map 16GiB -limit disk 50GiB -format 'Geometry: %G\nDepth: %[bit-depth]\nColorspace: %[colorspace]\nAlpha: %A\nMIME type: %m\n' #{path}"
+      memory_limit = ENV["IM_MEMORY_LIMIT"]
+      map_limit = ENV["IM_MAP_LIMIT"]
+      disk_limit = ENV["IM_DISK_LIMIT"]
+
+      cmd = "identify"
+
+      cmd += " -limit memory #{memory_limit}" if memory_limit.present?
+      cmd += " -limit map #{map_limit}" if map_limit.present?
+      cmd += " -limit disk #{disk_limit}" if disk_limit.present?
+
+      cmd += " -format 'Geometry: %G\nDepth: %[bit-depth]\nColorspace: %[colorspace]\nAlpha: %A\nMIME type: %m\n' #{path}"
+
       output, status = Open3.capture2(cmd)
       Rails.logger.info "Identify command output: #{output}"
       Rails.logger.info "Identify command status: #{status}"