Flutter Tutorial: Convert Canvas to Image

In Flutter, you can convert a Canvas to an image using the toImage() method from the ui.Image class. The Canvas class allows you to draw graphics and shapes on a custom widget or during the painting phase of a widget's CustomPainter. Once you've drawn everything on the canvas, you can then convert it to an image using the toImage() method.

Here's a step-by-step guide on how to convert a Canvas to an image in Flutter:

Import the required packages

import 'package:flutter/material.dart';
import 'dart:ui' as ui;

Create a custom widget or a CustomPainter where you'll draw on the canvas

class MyCanvasWidget extends StatelessWidget {
  Widget build(BuildContext context) {
    return CustomPaint(
      size: Size(200, 200), // Set the size of the canvas
      painter: MyCanvasPainter(),

class MyCanvasPainter extends CustomPainter {
  void paint(Canvas canvas, Size size) {
    // Draw on the canvas here
    // For example, draw a red circle at the center
    final Paint paint = Paint()..color = Colors.red;
    final double centerX = size.width / 2;
    final double centerY = size.height / 2;
    final double radius = 50.0;
    canvas.drawCircle(Offset(centerX, centerY), radius, paint);

  bool shouldRepaint(CustomPainter oldDelegate) {
    return false;

Create a function to convert the canvas to an image

Future<ui.Image> captureCanvasToImage() async {
  final pictureRecorder = ui.PictureRecorder();
  final canvas = Canvas(pictureRecorder);

  // Create the custom widget or draw on the canvas using a CustomPainter
  final widget = MyCanvasWidget();
  widget.paint(canvas, Size(200, 200)); // Set the size of the canvas to match the custom widget size

  final recordedPicture = pictureRecorder.endRecording();
  return await recordedPicture.toImage(200, 200); // Set the image size, should match the canvas size

Call the captureCanvasToImage() function and handle the image

void _convertCanvasToImage() async {
  ui.Image image = await captureCanvasToImage();
  // Use the image here as needed, such as displaying it in an `Image` widget or saving it to a file

In this example, we created a custom widget named MyCanvasWidget, which draws a red circle at the center of the canvas. The captureCanvasToImage() function creates a Canvas, draws on it using the custom widget or CustomPainter, and then converts it to an ui.Image.

Note that the canvas size should be set in both the custom widget (MyCanvasWidget) and the toImage() method to ensure that the drawing and image have the correct dimensions. In this example, we set the canvas size to 200x200, but you can adjust it to your desired dimensions.

Remember to handle errors and await the asynchronous operations properly when working with Futures and async functions. Also, make sure to call _convertCanvasToImage() when appropriate to capture the canvas and obtain the image.