381 helmert

ohmg/conf/http.py

@@ -38,10 +38,13 @@ def user_info_from_request(request):
         user_info["api_keys"] = user.api_keys
         user_info["is_authenticated"] = True
         user_info["is_staff"] = user.is_staff
+        user_info["perms"] = list(user.get_all_permissions())
+        print(json.dumps(user_info, indent=1))
     else:
         user_info = {
             "is_authenticated": False,
             "is_staff": False,
+            "perms": [],
         }
     return user_info
 

ohmg/core/migrations/0013_permissions.py

@@ -0,0 +1,24 @@
+# Generated by Django 4.2.27 on 2026-06-05 09:10
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0012_layerset_xyz_tiles_prefix'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Permissions',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+            ],
+            options={
+                'permissions': (('use_helmert', 'Can use Helmert transformation'),),
+                'managed': False,
+                'default_permissions': (),
+            },
+        ),
+    ]

ohmg/core/models/__init__.py

@@ -3,4 +3,5 @@
 from .layerset import LayerSet, LayerSetCategory  # noqa: F401
 from .map import Map  # noqa: F401
 from .mapgroup import MapGroup  # noqa: F401
+from .permissions import Permissions  # noqa: F401
 from .region import Region, RegionCategory  # noqa: F401

ohmg/core/models/permissions.py

@@ -0,0 +1,19 @@
+# Source - https://stackoverflow.com/a/37988537
+# Posted by Dmitry, modified by community. See post 'Timeline' for change history
+# Retrieved 2026-06-05, License - CC BY-SA 4.0
+
+from django.db import models
+
+
+class Permissions(models.Model):
+    """Permissions model for holding custom Django permissions objects
+    that are not tied to any specific model."""
+
+    class Meta:
+        managed = False  # No database table creation or deletion  \
+        # operations will be performed for this model.
+
+        default_permissions = ()  # disable "add", "change", "delete"
+        # and "view" default permissions
+
+        permissions = (("use_helmert", "Can use Helmert transformation"),)

ohmg/frontend/svelte_components/src/components/Georeferencer.svelte

@@ -54,6 +54,8 @@
   import InfoModalButton from './buttons/InfoModalButton.svelte';
   import SigninReminder from './common/SigninReminder.svelte';
 
+  import ConfirmModal from './modals/ConfirmModal.svelte';
+
   export let CONTEXT;
   export let REGION;
   export let MAP;
@@ -119,7 +121,7 @@
     leaveOkay = false;
     enableButtons = true;
   }
-  $: enableSave = gcpList.length >= 3 && enableButtons;
+  $: enableSave = gcpList.length >= minGCPs && enableButtons;
 
   let countdown = 10;
   let timer;
@@ -150,10 +152,42 @@
   const noteInputElId = 'note-input';
 
   let currentTransformation = 'poly1';
-  const transformations = [
-    { id: 'poly1', name: 'Polynomial' },
-    { id: 'tps', name: 'Thin Plate Spline' },
+  let minGCPs = 3;
+  $: transformations = [
+    {
+      id: 'poly1',
+      name: 'Polynomial',
+      enabled: true,
+      available: true
+    },
+    {
+      id: 'tps',
+      name: 'Thin Plate Spline',
+      enabled: true,
+      available: true
+    },
+    {
+      id: 'helmert',
+      name: 'Helmert 4-param',
+      enabled: gcpList.length == 2,
+      available: CONTEXT.user.perms.includes("core.use_helmert")
+    },
   ];
+  $: {
+    if (gcpList.length == 3 && currentTransformation == "helmert") {
+      currentTransformation = "poly1"
+    }
+    if (currentTransformation == "helmert") {
+      minGCPs = 2;
+    } else {
+      minGCPs = 3;
+    }
+  }
+  $: {
+    if (gcpList.length <= 2 && currentTransformation != "helmert") {
+      previewMode = "n/a"
+    }
+  }
 
   let currentTargetProjection = 'EPSG:3857';
   const availableProjections = [
@@ -703,7 +737,12 @@
   };
 
   function getPreview() {
-    if (gcpList.length < 3) {
+    if (currentTransformation == "helmert") {
+      minGCPs = 2;
+    } else {
+      minGCPs = 3;
+    }
+    if (gcpList.length < minGCPs) {
       previewMode = 'n/a';
       return;
     }
@@ -729,7 +768,7 @@
   }
 
   function submitSession() {
-    if (gcpList.length < 3) {
+    if (gcpList.length < minGCPs) {
       previewMode = 'n/a';
       return;
     }
@@ -869,6 +908,12 @@
   >
 </div>
 
+<ConfirmModal id="modal-submit-helmert" yesAction={submitSession}>
+  <p>
+    You have only two GCPs, but it is highly advisable to have three or more.
+    Please add more, unless you are unable to do so.
+  </p>
+</ConfirmModal>
 <Modal id="modal-anonymous">
   <SigninReminder next={CONTEXT.path} msg="Without an account you can experiment with the interface, but cannot submit your work."/>
 </Modal>
@@ -944,7 +989,13 @@
       <label><input type="checkbox" bind:checked={syncPanelWidth} /> autosize</label>
     </div>
     <div class="control-btn-group">
-      <ToolUIButton action={submitSession} title="Save control points" disabled={!enableSave}><Check /></ToolUIButton>
+      <ToolUIButton action={() => {
+        if (gcpList.length == 2) {
+          getModal('modal-submit-helmert').open()
+        } else {
+          submitSession()
+        }
+      }} title="Save control points" disabled={!enableSave}><Check /></ToolUIButton>
       <ToolUIButton
         action={() => {
           getModal('modal-cancel').open();
@@ -1010,7 +1061,9 @@
         Transformation:
         <select class="trans-select" style="width:151px;" bind:value={currentTransformation} on:change={getPreview}>
           {#each transformations as trans}
-            <option value={trans.id}>{trans.name}</option>
+            {#if trans.available}
+              <option value={trans.id} disabled={!trans.enabled}>{trans.name}</option>
+            {/if}
           {/each}
         </select>
       </label>

ohmg/frontend/svelte_components/src/components/modals/ConfirmModal.svelte

@@ -0,0 +1,32 @@
+<script>
+  import Modal, { getModal } from '../base/Modal.svelte';
+
+  export let id;
+  export let yesButtonText = "Yes"
+  export let noButtonText = "No"
+  export let yesAction = () => {};
+  export let noAction = () => {};
+
+</script>
+
+<Modal id={id} closable={false}>
+  <slot>
+    <p>"Confirm this action?"</p>
+  </slot>
+  <button
+    class="button is-success"
+    title={yesButtonText}
+    on:click={() => {
+      yesAction();
+      getModal(id).close();
+    }}>{yesButtonText}</button
+  >
+  <button
+    class="button is-danger"
+    title={noButtonText}
+    on:click={() => {
+      noAction()
+      getModal(id).close();
+    }}>{noButtonText}</button
+  >
+</Modal>

ohmg/georeference/geometry.py

@@ -0,0 +1,63 @@
+import math
+from typing import Tuple
+
+from django.contrib.gis.geos import LineString
+
+
+def angle_from_coords(pt1: Tuple[float, float], pt2: Tuple[float, float]) -> float:
+    """
+    Calculates the absolute Cartesian angle (in degrees) of the vector
+    pointing from p1 to p2, relative to the positive Y-axis.
+    """
+
+    # Calculate differences
+    dx = pt2[0] - pt1[0]
+    dy = pt2[1] - pt1[1]
+
+    # Calculate angle in radians (-pi to pi)
+    radians = math.atan2(dx, dy)
+
+    degrees = math.degrees(radians)
+
+    return degrees
+
+
+def extend_vector(
+    p1: Tuple[float, float],
+    p2: Tuple[float, float],
+    distance: float,
+) -> Tuple[float, float]:
+    """https://math.stackexchange.com/a/3346108 (credit to Oliver Roche)
+    takes the two input points, which represent a vector, and creates a
+    third point that would extend that vector by the given distance."""
+
+    x1, y1 = p1
+    x2, y2 = p2
+    rise = y2 - y1
+    run = x2 - x1
+
+    norm = math.sqrt((run**2) + (rise**2))
+
+    # if negative coords are used norm will be 0.0, silently return original point
+    if norm == 0.0:
+        return (x2, y2)
+
+    x3 = x2 + distance * (run / norm)
+    y3 = y2 + distance * (rise / norm)
+
+    return (x3, y3)
+
+
+def extend_linestring(linestring: LineString, distance: int = 10) -> LineString:
+    """takes the input GEOS LineString and extends it in both directions
+    (following the trajectory of each end segment) by the given distance."""
+
+    coord_list = list(linestring.coords)
+
+    new_start = extend_vector(coord_list[1], coord_list[0], distance)
+    new_end = extend_vector(coord_list[-2], coord_list[-1], distance)
+
+    coord_list.insert(0, new_start)
+    coord_list.append(new_end)
+
+    return LineString(coord_list)