From c1a5c91299b62299977d6e77be7f6a79cdf28cde Mon Sep 17 00:00:00 2001
From: Pete Matsyburka <pete@docuseal.com>
Date: Sat, 29 Nov 2025 20:13:00 +0200
Subject: [PATCH] adjust detection

---
 lib/pdfium.rb                    |  18 +++-
 lib/templates/detect_fields.rb   | 179 +++++++++++++------------------
 lib/templates/image_to_fields.rb |  29 +----
 3 files changed, 93 insertions(+), 133 deletions(-)

diff --git a/lib/pdfium.rb b/lib/pdfium.rb
index b43c3b20..6a5874e7 100644
--- a/lib/pdfium.rb
+++ b/lib/pdfium.rb
@@ -49,7 +49,15 @@ class Pdfium
     end
   end
 
-  LineNode = Struct.new(:x, :y, :w, :h, :tilt)
+  LineNode = Struct.new(:x, :y, :w, :h, :tilt) do
+    def endy
+      @endy ||= y + h
+    end
+
+    def endx
+      @endx ||= x + w
+    end
+  end
 
   # rubocop:disable Naming/ClassAndModuleCamelCase
   class FPDF_LIBRARY_CONFIG < FFI::Struct
@@ -480,7 +488,11 @@ class Pdfium
         @text_nodes << TextNode.new(char, x, y, node_width, node_height)
       end
 
-      @text_nodes = @text_nodes.sort { |a, b| a.y == b.y ? a.x <=> b.x : a.y <=> b.y }
+      y_threshold = 4.0 / width
+
+      @text_nodes = @text_nodes.sort do |a, b|
+        (a.endy - b.endy).abs < y_threshold ? a.x <=> b.x : a.endy <=> b.endy
+      end
     ensure
       Pdfium.FPDFText_ClosePage(text_page) if text_page && !text_page.null?
     end
@@ -549,7 +561,7 @@ class Pdfium
         @line_nodes << LineNode.new(norm_x, norm_y, norm_w, norm_h, tilt)
       end
 
-      @line_nodes = @line_nodes.sort { |a, b| a.y == b.y ? a.x <=> b.x : a.y <=> b.y }
+      @line_nodes = @line_nodes.sort { |a, b| a.endy == b.endy ? a.x <=> b.x : a.endy <=> b.endy }
     end
 
     def close
diff --git a/lib/templates/detect_fields.rb b/lib/templates/detect_fields.rb
index d3e35b05..46c613e7 100755
--- a/lib/templates/detect_fields.rb
+++ b/lib/templates/detect_fields.rb
@@ -4,7 +4,16 @@ module Templates
   module DetectFields
     module_function
 
-    TextFieldBox = Struct.new(:x, :y, :w, :h, keyword_init: true)
+    TextFieldBox = Struct.new(:x, :y, :w, :h, keyword_init: true) do
+      def endy
+        @endy ||= y + h
+      end
+
+      def endx
+        @endx ||= x + w
+      end
+    end
+
     PageNode = Struct.new(:prev, :next, :elem, :page, :attachment_uuid, keyword_init: true)
 
     DATE_REGEXP = /
@@ -49,6 +58,9 @@ module Templates
       \s*[:-]?\s*\z
     /ix
 
+    LINEBREAK = ["\n", "\r"].freeze
+    CHECBOXES = ['☐', '□'].freeze
+
     # rubocop:disable Metrics, Style
     def call(io, attachment: nil, confidence: 0.3, temperature: 1, inference: Templates::ImageToFields,
              nms: 0.1, split_page: false, aspect_ratio: true, padding: 20, regexp_type: true, &)
@@ -71,6 +83,8 @@ module Templates
       fields = inference.call(image, confidence:, nms:, split_page:,
                                      temperature:, aspect_ratio:, padding:)
 
+      fields = sort_fields(fields, y_threshold: 10.0 / image.height)
+
       fields = fields.map do |f|
         {
           uuid: SecureRandom.uuid,
@@ -113,6 +127,8 @@ module Templates
         text_fields = extract_text_fields_from_page(page)
         line_fields = extract_line_fields_from_page(page)
 
+        fields = sort_fields(fields, y_threshold: 10.0 / page.height)
+
         fields = increase_confidence_for_overlapping_fields(fields, text_fields)
         fields = increase_confidence_for_overlapping_fields(fields, line_fields)
 
@@ -153,6 +169,12 @@ module Templates
       doc.close
     end
 
+    def sort_fields(fields, y_threshold: 0.01)
+      fields.sort do |a, b|
+        (a.endy - b.endy).abs < y_threshold ? a.x <=> b.x : a.endy <=> b.endy
+      end
+    end
+
     def print_debug(head_node)
       current_node = head_node
       index = 0
@@ -189,121 +211,68 @@ module Templates
 
     def build_page_nodes(page, fields, tail_node, attachment_uuid: nil)
       field_nodes = []
-      current_text = ''.b
-
-      text_nodes = page.text_nodes
 
-      text_idx = 0
-      field_idx = 0
+      y_theshold = 10.0 / page.height
 
-      while text_idx < text_nodes.length || field_idx < fields.length
-        text_node = text_nodes[text_idx]
-        field = fields[field_idx]
+      text_nodes = page.text_nodes
 
-        process_text_node = false
-        process_field_node = false
+      current_field = fields.shift
 
-        if text_node && field
-          text_y_center = text_node.y + (text_node.h / 2.0)
-          field_y_center = field.y + (field.h / 2.0)
-          y_threshold = text_node.h / 2.0
-          vertical_distance = (text_y_center - field_y_center).abs
+      index = 0
 
-          if vertical_distance < y_threshold
-            is_underscore = text_node.content == '_'
-            is_left_of_field = text_node.x < field.x
+      prev_node = nil
 
-            if is_underscore && is_left_of_field
-              text_x_end = text_node.x + text_node.w
+      loop do
+        node = text_nodes[index]
 
-              distance = field.x - text_x_end
-              proximity_threshold = text_node.w * 3.0
+        break unless node
 
-              if distance < proximity_threshold
-                process_field_node = true
-              else
-                process_text_node = true
-              end
+        loop do
+          break unless current_field
 
-            elsif is_left_of_field
-              process_text_node = true
-            else
-              process_field_node = true
-            end
+          if ((current_field.endy - node.endy).abs < y_theshold &&
+              (current_field.x <= node.x || node.content.in?(LINEBREAK))) ||
+             current_field.endy < node.y
+            field_node = PageNode.new(prev: tail_node, elem: current_field, page: page.page_index, attachment_uuid:)
+            tail_node.next = field_node
+            tail_node = field_node
+            field_nodes << tail_node
 
-          elsif text_node.y < field.y
-            process_text_node = true
+            current_field = fields.shift
           else
-            process_field_node = true
+            break
           end
-
-        elsif text_node
-          process_text_node = true
-        elsif field
-          process_field_node = true
         end
 
-        if process_field_node
-          unless current_text.empty?
-            new_text_node = PageNode.new(prev: tail_node, elem: current_text, page: page.page_index, attachment_uuid:)
-            tail_node.next = new_text_node
-            tail_node = new_text_node
-            current_text = ''.b
-          end
+        if tail_node.elem.is_a?(Templates::ImageToFields::Field)
+          text_node = PageNode.new(prev: tail_node, elem: ''.b, page: page.page_index, attachment_uuid:)
+          tail_node.next = text_node
 
-          new_field_node = PageNode.new(prev: tail_node, elem: field, page: page.page_index, attachment_uuid:)
-          tail_node.next = new_field_node
-          tail_node = new_field_node
-
-          field_nodes << tail_node
-
-          while text_idx < text_nodes.length
-            text_node_to_check = text_nodes[text_idx]
-
-            is_part_of_field = false
-
-            if text_node_to_check.content == '_'
-              check_y_center = text_node_to_check.y + (text_node_to_check.h / 2.0)
-              check_y_dist = (check_y_center - field_y_center).abs
-              check_y_thresh = text_node_to_check.h / 2.0
-
-              if check_y_dist < check_y_thresh
-                padding = text_node_to_check.w * 3.0
-                field_x_start = field.x - padding
-                field_x_end = field.x + field.w + padding
-                text_x_start = text_node_to_check.x
-                text_x_end = text_node_to_check.x + text_node_to_check.w
-
-                is_part_of_field = true if text_x_start <= field_x_end && field_x_start <= text_x_end
-              end
-            end
-
-            break unless is_part_of_field
+          tail_node = text_node
+        end
 
-            text_idx += 1
-          end
+        if prev_node && (node.endy - prev_node.endy) > y_theshold && LINEBREAK.exclude?(prev_node.content)
+          tail_node.elem << "\n"
+        end
 
-          field_idx += 1
-        elsif process_text_node
-          if text_idx > 0
-            prev_text_node = text_nodes[text_idx - 1]
+        if node.content != '_' || !tail_node.elem.ends_with?('___')
+          tail_node.elem << node.content unless CHECBOXES.include?(node.content)
+        end
 
-            x_gap = text_node.x - (prev_text_node.x + prev_text_node.w)
+        prev_node = node
 
-            gap_w = text_node.w > prev_text_node.w ? text_node.w : prev_text_node.w
+        index += 1
+      end
 
-            current_text << ' ' if x_gap > gap_w * 2
-          end
+      loop do
+        break unless current_field
 
-          current_text << text_node.content
-          text_idx += 1
-        end
-      end
+        field_node = PageNode.new(prev: tail_node, elem: current_field, page: page.page_index, attachment_uuid:)
+        tail_node.next = field_node
+        tail_node = field_node
+        field_nodes << tail_node
 
-      unless current_text.empty?
-        new_text_node = PageNode.new(prev: tail_node, elem: current_text, page: page.page_index, attachment_uuid:)
-        tail_node.next = new_text_node
-        tail_node = new_text_node
+        current_field = fields.shift
       end
 
       [field_nodes, tail_node]
@@ -399,8 +368,8 @@ module Templates
 
         x1 = node.x
         y1 = node.y
-        x2 = node.x + node.w
-        y2 = node.y + node.h
+        x2 = node.endx
+        y2 = node.endy
 
         underscore_count = 1
 
@@ -417,8 +386,9 @@ module Templates
           break if distance > 0.02 || height_diff > node.h * 0.5
 
           underscore_count += 1
-          next_x2 = next_node.x + next_node.w
-          next_y2 = next_node.y + next_node.h
+
+          next_x2 = next_node.endx
+          next_y2 = next_node.endy
 
           x2 = next_x2
           y2 = [y2, next_y2].max
@@ -438,8 +408,8 @@ module Templates
     def calculate_iou(box1, box2)
       x1 = [box1.x, box2.x].max
       y1 = [box1.y, box2.y].max
-      x2 = [box1.x + box1.w, box2.x + box2.w].min
-      y2 = [box1.y + box1.h, box2.y + box2.h].min
+      x2 = [box1.endx, box2.endx].min
+      y2 = [box1.endy, box2.endy].min
 
       intersection_width = [0, x2 - x1].max
       intersection_height = [0, y2 - y1].max
@@ -455,8 +425,7 @@ module Templates
     end
 
     def boxes_overlap?(box1, box2)
-      !(box1.x + box1.w < box2.x || box2.x + box2.w < box1.x ||
-        box1.y + box1.h < box2.y || box2.y + box2.h < box1.y)
+      !(box1.endx < box2.x || box2.endx < box1.x || box1.endy < box2.y || box2.endy < box1.y)
     end
 
     def increase_confidence_for_overlapping_fields(image_fields, text_fields, by: 1.0)
@@ -465,12 +434,10 @@ module Templates
       image_fields.map do |image_field|
         next if image_field.type != 'text'
 
-        field_bottom = image_field.y + image_field.h
-
         text_fields.each do |text_field|
-          break if text_field.y > field_bottom
+          break if text_field.y > image_field.endy
 
-          next if text_field.y + text_field.h < image_field.y
+          next if text_field.endy < image_field.y
 
           next unless boxes_overlap?(image_field, text_field)
           next if calculate_iou(image_field, text_field) < 0.4
diff --git a/lib/templates/image_to_fields.rb b/lib/templates/image_to_fields.rb
index 72c578a7..d9c04221 100755
--- a/lib/templates/image_to_fields.rb
+++ b/lib/templates/image_to_fields.rb
@@ -8,6 +8,10 @@ module Templates
       def endy
         @endy ||= y + h
       end
+
+      def endx
+        @endx ||= x + w
+      end
     end
 
     MODEL_PATH = Rails.root.join('tmp/model.onnx')
@@ -64,9 +68,7 @@ module Templates
 
       detections = apply_nms(detections, nms)
 
-      fields = build_fields_from_detections(detections, image)
-
-      sort_fields(fields, y_threshold: 10.0 / image.height)
+      build_fields_from_detections(detections, image)
     end
 
     def build_split_image_regions(image)
@@ -302,27 +304,6 @@ module Templates
       end
     end
 
-    def sort_fields(fields, y_threshold: 0.01)
-      sorted_fields = fields.sort { |a, b| a.endy == b.endy ? a.x <=> b.x : a.endy <=> b.endy }
-
-      lines = []
-      current_line = []
-
-      sorted_fields.each do |field|
-        if current_line.blank? || (field.y - current_line.first.y).abs < y_threshold
-          current_line << field
-        else
-          lines << current_line.sort_by(&:x)
-
-          current_line = [field]
-        end
-      end
-
-      lines << current_line.sort_by(&:x) if current_line.present?
-
-      lines.flatten
-    end
-
     def apply_nms(detections, threshold = 0.5)
       return detections if detections[:xyxy].shape[0].zero?