fix: round caption edges the same way as the editor

Python round() uses ties-to-even, so a coordinate on a half step was one
unit off from Copy JSON, which rounds halves toward +inf.

nodes/ideogram4_nodes.py

@@ -2,6 +2,7 @@
 
 import json
 import logging
+import math
 import os
 import re
 
@@ -341,17 +342,26 @@ def _render_preview(boxes, width, height, bg_guid="", background_opacity=0.5):
     return torch.from_numpy(arr).unsqueeze(0)
 
 
+def _round_half_up(value):
+    """Nearest integer, halves toward +inf. Matches JS Math.round.
+
+    Python round() uses ties-to-even, so a caption edge on x.5 disagreed
+    with Copy JSON by one unit.
+    """
+    return int(math.floor(value + 0.5))
+
+
 def _scale_axis(value):
     """Map one finite axis onto Ideogram's integer 0-1000 range.
 
-    Clamp before rounding. round() raises OverflowError once value * 1000
-    exceeds the float range, which a hand-edited region can do.
+    Values outside 0-1 are clamped before scaling. A huge finite coordinate
+    used to overflow inside round().
     """
     if value >= 1:
         return 1000
     if value <= 0:
         return 0
-    return int(round(value * 1000))
+    return _round_half_up(value * 1000)
 
 
 def _box_coords(box):
@@ -399,7 +409,7 @@ def _preview_edges(box, rw, rh):
             return scale
         if value <= 0:
             return 0
-        return max(0, min(scale, int(round(value * scale))))
+        return max(0, min(scale, _round_half_up(value * scale)))
 
     x1, y1, x2, y2 = edge(x, rw), edge(y, rh), edge(x + w, rw), edge(y + h, rh)
     if x2 < x1:

tests/caption_layout.test.js

@@ -104,6 +104,8 @@ describe("ideogram bbox import", () => {
 
   it("exports a usable bbox and drops coordinates that are not finite", () => {
     assert.deepEqual(rectToIdeogramBbox({ x: 0.1, y: 0.2, w: 0.3, h: 0.4 }), [200, 100, 600, 400]);
+    // Halves go toward +inf, the same rule the prompt node uses.
+    assert.deepEqual(rectToIdeogramBbox({ x: 0.0025, y: 0.0005, w: 0.001, h: 0.001 }), [1, 3, 2, 4]);
     assert.deepEqual(rectToIdeogramBbox({ x: "0.1", y: "0.2", w: "0.3", h: "0.4" }), [200, 100, 600, 400]);
     assert.deepEqual(rectToIdeogramBbox({ x: 0.5, y: 0.6, w: -0.2, h: -0.1 }), [500, 300, 600, 500]);
     assert.equal(rectToIdeogramBbox({ x: Number.NaN, y: 0.2, w: 0.3, h: 0.4 }), null);

tests/test_nodes.py

@@ -86,6 +86,12 @@ class TestPromptHelpers(unittest.TestCase):
         result = _norm_bbox({"x": 1e308, "y": 0.0, "w": 1e308, "h": 0.2})
         self.assertEqual(result, [0, 1000, 200, 1000])
 
+    def test_norm_bbox_half_steps_round_like_the_editor(self):
+        # 2.5 and 0.5. Copy JSON uses JS Math.round (half toward +inf).
+        # Python round() uses ties-to-even, which made the prompt one unit off.
+        box = {"x": 0.0025, "y": 0.0005, "w": 0.001, "h": 0.001}
+        self.assertEqual(_norm_bbox(box), [1, 3, 2, 4])
+
     def test_elements_from_boxes_omits_unusable_bbox(self):
         elements = _elements_from_boxes([
             {"type": "obj", "desc": "bad", "x": "nope", "y": 0, "w": 0.2, "h": 0.2},
@@ -111,6 +117,12 @@ class TestPromptHelpers(unittest.TestCase):
             (10, 10, 40, 30),
         )
 
+    def test_preview_edges_half_pixel_rounds_like_the_editor(self):
+        self.assertEqual(
+            _preview_edges({"x": 0.005, "y": 0, "w": 0.01, "h": 0.02}, 100, 100),
+            (1, 0, 2, 2),
+        )
+
     def test_elements_keep_schema_types_when_fields_are_not_strings(self):
         elements = _elements_from_boxes([
             {