diff --git a/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/ocr-template-editor.component.ts b/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/ocr-template-editor.component.ts
index e240fca0c..97c094a0a 100644
--- a/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/ocr-template-editor.component.ts
+++ b/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/ocr-template-editor.component.ts
@@ -52,15 +52,21 @@ import { DocumentTypeService } from 'src/app/services/rest/document-type.service
 import { DocumentService } from 'src/app/services/rest/document.service'
 import { OcrTemplateService } from 'src/app/services/rest/ocr-template.service'
 import { ToastService } from 'src/app/services/toast.service'
-
-interface DrawingRect {
-  startX: number
-  startY: number
-  endX: number
-  endY: number
-}
-
-type ResizeHandle = 'n' | 's' | 'e' | 'w' | 'ne' | 'nw' | 'se' | 'sw'
+import {
+  DisplayRect,
+  DrawingRect,
+  findHandleAt,
+  findZoneAt,
+  getZoneDisplayRect,
+  getZonePage,
+  HANDLE_SIZE,
+  isZoneOnPage,
+  MoveStart,
+  moveZone,
+  ResizeHandle,
+  resizeZone,
+  sourceRectFromDrawing,
+} from './zone-geometry'
 
 type ActiveTab = 'settings' | 'zones' | 'zone'
 
@@ -147,11 +153,10 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
   isResizing = false
   resizeHandle: ResizeHandle | null = null
   resizeZoneIndex: number | null = null
-  private readonly HANDLE_SIZE = 8
 
   isMoving = false
   moveZoneIndex: number | null = null
-  private moveStart = { mouseX: 0, mouseY: 0, zoneX: 0, zoneY: 0 }
+  private moveStart: MoveStart = { mouseX: 0, mouseY: 0, zoneX: 0, zoneY: 0 }
 
   zoneTestResult: OcrZoneTestResult | null = null
   zoneTesting = false
@@ -340,13 +345,11 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
   }
 
   zonePage(zone: OcrTemplateZone): number {
-    const v = zone.page ?? 1
-    if (v === -1) return this.previewPageCount ?? this.previewPage + 1
-    return v >= 1 ? v : 1
+    return getZonePage(zone, this.previewPage, this.previewPageCount)
   }
 
   private isOnCurrentPage(zone: OcrTemplateZone): boolean {
-    return this.zonePage(zone) === this.previewPage + 1
+    return isZoneOnPage(zone, this.previewPage, this.previewPageCount)
   }
 
   onImageLoad() {
@@ -364,7 +367,7 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
     const y = event.clientY - rect.top
 
     if (this.selectedZoneIndex !== null) {
-      const handle = this.findHandleAt(x, y, this.selectedZoneIndex)
+      const handle = this.findHandleAt({ x, y }, this.selectedZoneIndex)
       if (handle) {
         this.isResizing = true
         this.resizeHandle = handle
@@ -373,7 +376,7 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
       }
     }
 
-    const clickedIdx = this.findZoneAt(x, y)
+    const clickedIdx = this.findZoneAt({ x, y })
     if (clickedIdx !== null && !event.shiftKey) {
       this.selectZone(clickedIdx)
       const zone = this.template.zones[clickedIdx]
@@ -401,22 +404,12 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
     }
 
     if (this.isMoving && this.moveZoneIndex !== null) {
-      const zone = this.template.zones[this.moveZoneIndex]
-      const canvas = this.canvasRef.nativeElement
-      const img = this.imageRef.nativeElement
-      const srcW = zone.zone_source_width || img.naturalWidth
-      const srcH = zone.zone_source_height || img.naturalHeight
-      const scaleX = srcW / canvas.width
-      const scaleY = srcH / canvas.height
-      const dx = Math.round((mx - this.moveStart.mouseX) * scaleX)
-      const dy = Math.round((my - this.moveStart.mouseY) * scaleY)
-      zone.x = Math.max(
-        0,
-        Math.min(this.moveStart.zoneX + dx, srcW - zone.width)
-      )
-      zone.y = Math.max(
-        0,
-        Math.min(this.moveStart.zoneY + dy, srcH - zone.height)
+      moveZone(
+        this.template.zones[this.moveZoneIndex],
+        { x: mx, y: my },
+        this.moveStart,
+        this.canvasSize(),
+        this.imageNaturalSize()
       )
       this.redrawCanvas()
       return
@@ -432,7 +425,7 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
     // Cursor feedback: resize handle > move (over a zone) > crosshair.
     const canvas = this.canvasRef.nativeElement
     if (this.selectedZoneIndex !== null) {
-      const handle = this.findHandleAt(mx, my, this.selectedZoneIndex)
+      const handle = this.findHandleAt({ x: mx, y: my }, this.selectedZoneIndex)
       if (handle) {
         const cursorMap: Record<ResizeHandle, string> = {
           nw: 'nw-resize',
@@ -449,7 +442,7 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
       }
     }
     canvas.style.cursor =
-      this.findZoneAt(mx, my) !== null ? 'move' : 'crosshair'
+      this.findZoneAt({ x: mx, y: my }) !== null ? 'move' : 'crosshair'
   }
 
   onCanvasMouseUp(event: MouseEvent) {
@@ -466,27 +459,15 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
     if (!this.isDrawing || !this.currentRect) return
     this.isDrawing = false
 
-    const canvas = this.canvasRef.nativeElement
     const img = this.imageRef.nativeElement
-
-    const scaleX = img.naturalWidth / canvas.width
-    const scaleY = img.naturalHeight / canvas.height
-
-    const x = Math.round(
-      Math.min(this.currentRect.startX, this.currentRect.endX) * scaleX
-    )
-    const y = Math.round(
-      Math.min(this.currentRect.startY, this.currentRect.endY) * scaleY
-    )
-    const w = Math.round(
-      Math.abs(this.currentRect.endX - this.currentRect.startX) * scaleX
-    )
-    const h = Math.round(
-      Math.abs(this.currentRect.endY - this.currentRect.startY) * scaleY
+    const rect = sourceRectFromDrawing(
+      this.currentRect,
+      this.canvasSize(),
+      this.imageNaturalSize()
     )
 
     // Ignore tiny accidental clicks.
-    if (w < 10 || h < 10) {
+    if (rect.w < 10 || rect.h < 10) {
       this.currentRect = null
       this.redrawCanvas()
       return
@@ -497,10 +478,10 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
       target: 'custom_field',
       custom_field:
         this.customFields.length > 0 ? this.customFields[0].id : null,
-      x,
-      y,
-      width: w,
-      height: h,
+      x: rect.x,
+      y: rect.y,
+      width: rect.w,
+      height: rect.h,
       page: this.previewPage + 1,
       ocr_language: 'deu+eng',
       transform: 'strip',
@@ -533,110 +514,51 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
     this.currentRect = null
   }
 
-  private getZoneDisplayRect(
-    zoneIdx: number
-  ): { x: number; y: number; w: number; h: number } | null {
+  private getZoneDisplayRect(zoneIdx: number): DisplayRect | null {
     const canvas = this.canvasRef?.nativeElement
     const img = this.imageRef?.nativeElement
     if (!canvas || !img || !img.naturalWidth) return null
     const zone = this.template.zones[zoneIdx]
     if (!zone) return null
     if (!this.isOnCurrentPage(zone)) return null
-    const srcW = zone.zone_source_width || img.naturalWidth
-    const srcH = zone.zone_source_height || img.naturalHeight
-    const scaleX = canvas.width / srcW
-    const scaleY = canvas.height / srcH
-    return {
-      x: zone.x * scaleX,
-      y: zone.y * scaleY,
-      w: zone.width * scaleX,
-      h: zone.height * scaleY,
-    }
+    return getZoneDisplayRect(zone, this.canvasSize(), this.imageNaturalSize())
   }
 
   private findHandleAt(
-    mx: number,
-    my: number,
+    point: { x: number; y: number },
     zoneIdx: number
   ): ResizeHandle | null {
     const r = this.getZoneDisplayRect(zoneIdx)
     if (!r) return null
-    const hs = this.HANDLE_SIZE
-    const handles: [ResizeHandle, number, number][] = [
-      ['nw', r.x, r.y],
-      ['n', r.x + r.w / 2, r.y],
-      ['ne', r.x + r.w, r.y],
-      ['w', r.x, r.y + r.h / 2],
-      ['e', r.x + r.w, r.y + r.h / 2],
-      ['sw', r.x, r.y + r.h],
-      ['s', r.x + r.w / 2, r.y + r.h],
-      ['se', r.x + r.w, r.y + r.h],
-    ]
-    for (const [name, hx, hy] of handles) {
-      if (Math.abs(mx - hx) <= hs && Math.abs(my - hy) <= hs) return name
-    }
-    return null
+    return findHandleAt(point, r)
   }
 
   private applyResize(mx: number, my: number) {
     if (this.resizeZoneIndex === null || !this.resizeHandle) return
 
-    const canvas = this.canvasRef.nativeElement
-    const img = this.imageRef.nativeElement
     const zone = this.template.zones[this.resizeZoneIndex]
     if (!zone) return
-    const srcW = zone.zone_source_width || img.naturalWidth
-    const srcH = zone.zone_source_height || img.naturalHeight
-    const scaleX = srcW / canvas.width
-    const scaleY = srcH / canvas.height
-    const imgX = Math.max(0, Math.min(srcW, Math.round(mx * scaleX)))
-    const imgY = Math.max(0, Math.min(srcH, Math.round(my * scaleY)))
-    const handle = this.resizeHandle
-
-    if (handle.includes('w')) {
-      const right = Math.min(zone.x + zone.width, srcW)
-      zone.x = Math.max(0, Math.min(imgX, right - 10))
-      zone.width = right - zone.x
-    }
-    if (handle.includes('e')) {
-      zone.width = Math.max(10, imgX - zone.x)
-    }
-    if (handle.includes('n')) {
-      const bottom = Math.min(zone.y + zone.height, srcH)
-      zone.y = Math.max(0, Math.min(imgY, bottom - 10))
-      zone.height = bottom - zone.y
-    }
-    if (handle.includes('s')) {
-      zone.height = Math.max(10, imgY - zone.y)
-    }
+    resizeZone(
+      zone,
+      this.resizeHandle,
+      { x: mx, y: my },
+      this.canvasSize(),
+      this.imageNaturalSize()
+    )
   }
 
-  private findZoneAt(displayX: number, displayY: number): number | null {
-    const canvas = this.canvasRef.nativeElement
+  private findZoneAt(point: { x: number; y: number }): number | null {
     const img = this.imageRef.nativeElement
     if (!img.naturalWidth) return null
 
-    for (let i = this.template.zones.length - 1; i >= 0; i--) {
-      const z = this.template.zones[i]
-      if (!this.isOnCurrentPage(z)) continue
-      const srcW = z.zone_source_width || img.naturalWidth
-      const srcH = z.zone_source_height || img.naturalHeight
-      const scaleX = canvas.width / srcW
-      const scaleY = canvas.height / srcH
-      const zx = z.x * scaleX
-      const zy = z.y * scaleY
-      const zw = z.width * scaleX
-      const zh = z.height * scaleY
-      if (
-        displayX >= zx &&
-        displayX <= zx + zw &&
-        displayY >= zy &&
-        displayY <= zy + zh
-      ) {
-        return i
-      }
-    }
-    return null
+    return findZoneAt(
+      point,
+      this.template.zones,
+      this.previewPage,
+      this.previewPageCount,
+      this.canvasSize(),
+      this.imageNaturalSize()
+    )
   }
 
   redrawCanvas() {
@@ -703,7 +625,6 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
       ctx.textBaseline = 'alphabetic'
 
       if (idx === this.selectedZoneIndex) {
-        const hs = this.HANDLE_SIZE
         ctx.fillStyle = color
         const handles = [
           [x, y],
@@ -716,7 +637,12 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
           [x + w, y + h],
         ]
         for (const [hx, hy] of handles) {
-          ctx.fillRect(hx - hs / 2, hy - hs / 2, hs, hs)
+          ctx.fillRect(
+            hx - HANDLE_SIZE / 2,
+            hy - HANDLE_SIZE / 2,
+            HANDLE_SIZE,
+            HANDLE_SIZE
+          )
         }
       }
     })
@@ -734,6 +660,16 @@ export class OcrTemplateEditorComponent implements OnInit, OnDestroy {
     }
   }
 
+  private canvasSize() {
+    const canvas = this.canvasRef.nativeElement
+    return { width: canvas.width, height: canvas.height }
+  }
+
+  private imageNaturalSize() {
+    const img = this.imageRef.nativeElement
+    return { width: img.naturalWidth, height: img.naturalHeight }
+  }
+
   removeZone(index: number) {
     this.template.zones.splice(index, 1)
     if (this.selectedZoneIndex === index) {
diff --git a/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/zone-geometry.spec.ts b/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/zone-geometry.spec.ts
new file mode 100644
index 000000000..84783b432
--- /dev/null
+++ b/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/zone-geometry.spec.ts
@@ -0,0 +1,140 @@
+import { OcrTemplateZone } from 'src/app/data/ocr-template'
+import {
+  findHandleAt,
+  findZoneAt,
+  getZoneDisplayRect,
+  getZonePage,
+  isZoneOnPage,
+  moveZone,
+  resizeZone,
+  sourceRectFromDrawing,
+} from './zone-geometry'
+
+function zone(overrides: Partial<OcrTemplateZone> = {}): OcrTemplateZone {
+  return {
+    name: 'Zone',
+    target: 'custom_field',
+    custom_field: 1,
+    x: 100,
+    y: 200,
+    width: 300,
+    height: 400,
+    page: 1,
+    ocr_language: 'eng',
+    transform: 'strip',
+    validation_regex: '',
+    order: 0,
+    ...overrides,
+  }
+}
+
+describe('OCR template editor geometry', () => {
+  it('normalizes zone pages', () => {
+    expect(getZonePage(zone({ page: 2 }), 0, 5)).toBe(2)
+    expect(getZonePage(zone({ page: -1 }), 0, 5)).toBe(5)
+    expect(getZonePage(zone({ page: -1 }), 2, null)).toBe(3)
+    expect(getZonePage(zone({ page: 0 }), 0, 5)).toBe(1)
+    expect(getZonePage(zone({ page: undefined }), 0, 5)).toBe(1)
+  })
+
+  it('checks whether a zone is on the current preview page', () => {
+    expect(isZoneOnPage(zone({ page: 2 }), 1, 5)).toBe(true)
+    expect(isZoneOnPage(zone({ page: 2 }), 0, 5)).toBe(false)
+    expect(isZoneOnPage(zone({ page: -1 }), 4, 5)).toBe(true)
+  })
+
+  it('scales source coordinates to canvas display coordinates', () => {
+    expect(
+      getZoneDisplayRect(
+        zone({ x: 100, y: 200, width: 300, height: 400 }),
+        { width: 500, height: 1000 },
+        { width: 1000, height: 2000 }
+      )
+    ).toEqual({ x: 50, y: 100, w: 150, h: 200 })
+  })
+
+  it('uses per-zone source dimensions when present', () => {
+    expect(
+      getZoneDisplayRect(
+        zone({
+          x: 100,
+          y: 100,
+          width: 100,
+          height: 100,
+          zone_source_width: 1000,
+          zone_source_height: 1000,
+        }),
+        { width: 500, height: 500 },
+        { width: 2000, height: 2000 }
+      )
+    ).toEqual({ x: 50, y: 50, w: 50, h: 50 })
+  })
+
+  it('finds zones from topmost to bottommost on the current page', () => {
+    const zones = [
+      zone({ name: 'first', x: 0, y: 0, width: 100, height: 100, page: 1 }),
+      zone({ name: 'second', x: 0, y: 0, width: 50, height: 50, page: 1 }),
+      zone({ name: 'third', x: 0, y: 0, width: 50, height: 50, page: 2 }),
+    ]
+
+    expect(
+      findZoneAt(
+        { x: 25, y: 25 },
+        zones,
+        0,
+        2,
+        { width: 100, height: 100 },
+        { width: 100, height: 100 }
+      )
+    ).toBe(1)
+  })
+
+  it('finds resize handles around a display rect', () => {
+    const rect = { x: 10, y: 20, w: 100, h: 200 }
+
+    expect(findHandleAt({ x: 10, y: 20 }, rect)).toBe('nw')
+    expect(findHandleAt({ x: 110, y: 220 }, rect)).toBe('se')
+    expect(findHandleAt({ x: 60, y: 20 }, rect)).toBe('n')
+    expect(findHandleAt({ x: 90, y: 160 }, rect)).toBeNull()
+  })
+
+  it('moves zones without leaving source image bounds', () => {
+    const z = zone({ x: 50, y: 50, width: 100, height: 100 })
+
+    moveZone(
+      z,
+      { x: 500, y: 500 },
+      { mouseX: 50, mouseY: 50, zoneX: 50, zoneY: 50 },
+      { width: 500, height: 500 },
+      { width: 500, height: 500 }
+    )
+
+    expect(z.x).toBe(400)
+    expect(z.y).toBe(400)
+  })
+
+  it('resizes zones without leaving source image bounds', () => {
+    const z = zone({ x: 50, y: 50, width: 100, height: 100 })
+
+    resizeZone(
+      z,
+      'se',
+      { x: 500, y: 500 },
+      { width: 500, height: 500 },
+      { width: 200, height: 200 }
+    )
+
+    expect(z.width).toBe(150)
+    expect(z.height).toBe(150)
+  })
+
+  it('converts drawn canvas rectangles to source rectangles', () => {
+    expect(
+      sourceRectFromDrawing(
+        { startX: 100, startY: 200, endX: 50, endY: 100 },
+        { width: 500, height: 1000 },
+        { width: 1000, height: 2000 }
+      )
+    ).toEqual({ x: 100, y: 200, w: 100, h: 200 })
+  })
+})
diff --git a/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/zone-geometry.ts b/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/zone-geometry.ts
new file mode 100644
index 000000000..489dd58ba
--- /dev/null
+++ b/src-ui/src/app/components/manage/ocr-templates/ocr-template-editor/zone-geometry.ts
@@ -0,0 +1,201 @@
+import { OcrTemplateZone } from 'src/app/data/ocr-template'
+
+export interface DrawingRect {
+  startX: number
+  startY: number
+  endX: number
+  endY: number
+}
+
+export interface Dimensions {
+  width: number
+  height: number
+}
+
+export interface Point {
+  x: number
+  y: number
+}
+
+export interface DisplayRect {
+  x: number
+  y: number
+  w: number
+  h: number
+}
+
+export interface MoveStart {
+  mouseX: number
+  mouseY: number
+  zoneX: number
+  zoneY: number
+}
+
+export type ResizeHandle = 'n' | 's' | 'e' | 'w' | 'ne' | 'nw' | 'se' | 'sw'
+
+export const HANDLE_SIZE = 8
+export const MIN_ZONE_SIZE = 10
+
+export function getZonePage(
+  zone: OcrTemplateZone,
+  previewPage: number,
+  previewPageCount: number | null
+): number {
+  const page = zone.page ?? 1
+  if (page === -1) return previewPageCount ?? previewPage + 1
+  return page >= 1 ? page : 1
+}
+
+export function isZoneOnPage(
+  zone: OcrTemplateZone,
+  previewPage: number,
+  previewPageCount: number | null
+): boolean {
+  return getZonePage(zone, previewPage, previewPageCount) === previewPage + 1
+}
+
+export function getZoneSourceSize(
+  zone: OcrTemplateZone,
+  imageSize: Dimensions
+): Dimensions {
+  return {
+    width: zone.zone_source_width || imageSize.width,
+    height: zone.zone_source_height || imageSize.height,
+  }
+}
+
+export function getZoneDisplayRect(
+  zone: OcrTemplateZone,
+  canvasSize: Dimensions,
+  imageSize: Dimensions
+): DisplayRect {
+  const sourceSize = getZoneSourceSize(zone, imageSize)
+  const scaleX = canvasSize.width / sourceSize.width
+  const scaleY = canvasSize.height / sourceSize.height
+
+  return {
+    x: zone.x * scaleX,
+    y: zone.y * scaleY,
+    w: zone.width * scaleX,
+    h: zone.height * scaleY,
+  }
+}
+
+export function findHandleAt(
+  point: Point,
+  rect: DisplayRect,
+  handleSize = HANDLE_SIZE
+): ResizeHandle | null {
+  const handles: [ResizeHandle, number, number][] = [
+    ['nw', rect.x, rect.y],
+    ['n', rect.x + rect.w / 2, rect.y],
+    ['ne', rect.x + rect.w, rect.y],
+    ['w', rect.x, rect.y + rect.h / 2],
+    ['e', rect.x + rect.w, rect.y + rect.h / 2],
+    ['sw', rect.x, rect.y + rect.h],
+    ['s', rect.x + rect.w / 2, rect.y + rect.h],
+    ['se', rect.x + rect.w, rect.y + rect.h],
+  ]
+
+  return (
+    handles.find(
+      ([, x, y]) =>
+        Math.abs(point.x - x) <= handleSize &&
+        Math.abs(point.y - y) <= handleSize
+    )?.[0] ?? null
+  )
+}
+
+export function findZoneAt(
+  point: Point,
+  zones: OcrTemplateZone[],
+  previewPage: number,
+  previewPageCount: number | null,
+  canvasSize: Dimensions,
+  imageSize: Dimensions
+): number | null {
+  for (let i = zones.length - 1; i >= 0; i--) {
+    const zone = zones[i]
+    if (!isZoneOnPage(zone, previewPage, previewPageCount)) continue
+    const rect = getZoneDisplayRect(zone, canvasSize, imageSize)
+
+    if (
+      point.x >= rect.x &&
+      point.x <= rect.x + rect.w &&
+      point.y >= rect.y &&
+      point.y <= rect.y + rect.h
+    ) {
+      return i
+    }
+  }
+
+  return null
+}
+
+export function moveZone(
+  zone: OcrTemplateZone,
+  point: Point,
+  moveStart: MoveStart,
+  canvasSize: Dimensions,
+  imageSize: Dimensions
+) {
+  const sourceSize = getZoneSourceSize(zone, imageSize)
+  const scaleX = sourceSize.width / canvasSize.width
+  const scaleY = sourceSize.height / canvasSize.height
+  const dx = Math.round((point.x - moveStart.mouseX) * scaleX)
+  const dy = Math.round((point.y - moveStart.mouseY) * scaleY)
+
+  zone.x = clamp(moveStart.zoneX + dx, 0, sourceSize.width - zone.width)
+  zone.y = clamp(moveStart.zoneY + dy, 0, sourceSize.height - zone.height)
+}
+
+export function resizeZone(
+  zone: OcrTemplateZone,
+  handle: ResizeHandle,
+  point: Point,
+  canvasSize: Dimensions,
+  imageSize: Dimensions
+) {
+  const sourceSize = getZoneSourceSize(zone, imageSize)
+  const scaleX = sourceSize.width / canvasSize.width
+  const scaleY = sourceSize.height / canvasSize.height
+  const imageX = clamp(Math.round(point.x * scaleX), 0, sourceSize.width)
+  const imageY = clamp(Math.round(point.y * scaleY), 0, sourceSize.height)
+
+  if (handle.includes('w')) {
+    const right = Math.min(zone.x + zone.width, sourceSize.width)
+    zone.x = clamp(imageX, 0, right - MIN_ZONE_SIZE)
+    zone.width = right - zone.x
+  }
+  if (handle.includes('e')) {
+    zone.width = Math.max(MIN_ZONE_SIZE, imageX - zone.x)
+  }
+  if (handle.includes('n')) {
+    const bottom = Math.min(zone.y + zone.height, sourceSize.height)
+    zone.y = clamp(imageY, 0, bottom - MIN_ZONE_SIZE)
+    zone.height = bottom - zone.y
+  }
+  if (handle.includes('s')) {
+    zone.height = Math.max(MIN_ZONE_SIZE, imageY - zone.y)
+  }
+}
+
+export function sourceRectFromDrawing(
+  rect: DrawingRect,
+  canvasSize: Dimensions,
+  imageSize: Dimensions
+): DisplayRect {
+  const scaleX = imageSize.width / canvasSize.width
+  const scaleY = imageSize.height / canvasSize.height
+
+  return {
+    x: Math.round(Math.min(rect.startX, rect.endX) * scaleX),
+    y: Math.round(Math.min(rect.startY, rect.endY) * scaleY),
+    w: Math.round(Math.abs(rect.endX - rect.startX) * scaleX),
+    h: Math.round(Math.abs(rect.endY - rect.startY) * scaleY),
+  }
+}
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.max(min, Math.min(value, max))
+}