first commit

lib/thermal priting invoices/sticker_image_generation.dart

@@ -0,0 +1,57 @@
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+
+Future<Uint8List?> createImageFromWidget(BuildContext context, Widget widget, {Duration? wait, Size? logicalSize, Size? imageSize}) async {
+  final repaintBoundary = RenderRepaintBoundary();
+
+  logicalSize ??= View.of(context).physicalSize / View.of(context).devicePixelRatio;
+  imageSize ??= View.of(context).physicalSize;
+
+  assert(logicalSize.aspectRatio == imageSize.aspectRatio, 'logicalSize and imageSize must not be the same');
+
+  final renderView = RenderView(
+      child: RenderPositionedBox(alignment: Alignment.center, child: repaintBoundary),
+      configuration: ViewConfiguration(
+        physicalConstraints: BoxConstraints.tight(logicalSize),
+        logicalConstraints: BoxConstraints.tight(logicalSize),
+        devicePixelRatio: 1,
+      ),
+      view: View.of(context) //PlatformDispatcher.instance.views.first,
+      );
+
+  final pipelineOwner = PipelineOwner();
+  final buildOwner = BuildOwner(focusManager: FocusManager());
+
+  pipelineOwner.rootNode = renderView;
+  renderView.prepareInitialFrame();
+
+  final rootElement = RenderObjectToWidgetAdapter<RenderBox>(
+      container: repaintBoundary,
+      child: Directionality(
+        textDirection: TextDirection.ltr,
+        child: widget,
+      )).attachToRenderTree(buildOwner);
+
+  buildOwner.buildScope(rootElement);
+
+  if (wait != null) {
+    await Future.delayed(wait);
+  }
+
+  buildOwner
+    ..buildScope(rootElement)
+    ..finalizeTree();
+
+  pipelineOwner
+    ..flushLayout()
+    ..flushCompositingBits()
+    ..flushPaint();
+
+  final image = await repaintBoundary.toImage(pixelRatio: imageSize.width / logicalSize.width);
+  final byteData = await image.toByteData(format: ui.ImageByteFormat.png);
+
+  return byteData?.buffer.asUint8List();
+}