How to convert image to uint8list in flutter without using async? - image

Question

PdfImage requires Uint8List as param but I have ImageProvider. So how can we convert image to uint8list in flutter?
var imageProvider = AssetImage('assets/test.jpg');
final image = PdfImage(
pdf.document,
image:???, /// Uint8List required
width: img.width,
height: img.height,
);
Using FutureBuilder:

Answer 1

Use rootBundle.load()
(await rootBundle.load(/*YOUR IMAGE PATH HERE*/)).buffer.asUint8List()
UPDATE
As load() is an async operation, you need to wait until the data is fully loaded. Try substituting the UI with some loading indicator until then.
ByteData imageData;
#override
void initState() {
rootBundle.load('assets/test.jpg')
.then((data) => setState(() => this.imageData = data));
}
#override
Widget build(BuildContext context) {
if (imageData == null) {
return Center(child: CircularProgressIndicator());
}
final image = PdfImage(
pdf.document,
image: imageData.buffer.asUint8List(),
width: img.width,
height: img.height,
);
...
}

Answer 2

I tried different solutions to convert image to UInt8List and finally found one Solution. It worked for me.
XFile? image = await imagePicker.pickImage(
source: ImageSource.gallery,
); // Upload file from gallery
final bytes = await image!.readAsBytes(); // Converts the file to UInt8List
for the output, i used MemoryImage
MemoryImage(bytes!);

Answer 3

in Flutter, attaching local image to pdf file.
Actually It's a simple solution to add our local image to pdf file.
just copy paste the following code and try
final ByteData bytes = await rootBundle.load('assets/logo.jpg');
final Uint8List list = bytes.buffer.asUint8List();
final image = PdfImage.file(
pdf.document,
bytes: list,
);
pdf.addPage(pw.Page(build: (pw.Context context) {
return pw.Center(
child: pw.Image(image),
); // Center
}));

Answer 4

You could split initState into two if you prefer:
#override
void initState() {
loadAsset('test.jpg');
}
void loadAsset(string name) async {
var data = await rootBundle.load('assets/$name');
setState(() => this.imageData = data);
}
Note that this will cause build() to run an extra time but I find it easier on the eye. With Michael's circular Indicator, this is a harmless extra cycle.