I have been really cracking my head trying to write and read png files into a folder in Windows Phone 8. From few blogs sites and codeplex i found that the there is an extension to the WritableBitmap Class which provides few extra functionalities. ImageTools has PNG encoder and decoder. But I really cant find examples to use them.
What Im trying to achieve here is to create a folder called page and then in it a file called Ink File. I want to convert the bitmap to a PNG and store it there. The bitmap is created from the strokes drawn on a canvas. The class ImageTools provides a function called ToImage to convert the strokes from the canvas to image.
For storing
ExtendedImage myImage = InkCanvas.ToImage();
var encoder = new PngEncoder();
var dataFolder = await local.CreateFolderAsync("Page", CreationCollisionOption.OpenIfExists);
StorageFile Ink_File = await dataFolder.CreateFileAsync("InkFile", CreationCollisionOption.ReplaceExisting);
using (var stream = await Ink_File.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
{
using (var s = await Ink_File.OpenStreamForWriteAsync())
{
encoder.Encode(myImage, s);
await s.FlushAsync();
s.Close();
}
}
Is this a correct method? I receive some null exceptions for this. How do i find if the image is saved as png. How is this image saved? Is it encoded and saved in a file or is it saved as a png itsef. And how do we read this back?
I have checked out this, this , this and lot more like this.
I'm developing app for WP8
I have used the PNG Writer Library found in ToolStack and it works :)
Related
I am using the multiple file picker package on pub.dev, the link is below https://pub.dev/packages/multi_image_picker in conjunction with the image cropper package by Yalantis
https://pub.dev/packages/image_cropper
to let my user pick multiple images and then crop them at will.
I am using this code to convert my asset into a file and feed it into the cropper. And it works.
final temp = await Directory.systemTemp.createTemp();
final data = await finalList[index].getByteData();
File failo = await File('${temp.path}/img').writeAsBytes(
data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes));
print("The path is ${temp.path}");
File croppedFailo = await ImageCropper.cropImage(
sourcePath: failo.path,
androidUiSettings: AndroidUiSettings(toolbarTitle: "My App"),
);
The tricky bit is to convert it back to an asset so that i can replace the old uncropped asset with this new cropped one..I read through the Asset documentation of the package and I tried this but it made my app crash
Asset croppedPic = new Asset(
croppedFailo.path,
DateTime.now().millisecondsSinceEpoch.toString(),
300,
300,
);
finalList.replaceRange(index, index + 1, [croppedPic]);
EDIT: When i say "asset", i am not referring to images i manually added to the assets/images folder in the app. The multi image picker plugin has a file- type called asset in which it returns images. That is the type to which i want to convert my file back into.
Never mind. I figured it's too unnecessarily complicated to do that. So, i instead just reformatted my entire code to handle images as files instead of assets. And, it actually made my life a lot simpler coz files give you more versatility and less problems than assets.
I am building an app in flutter and I want to store many images. So will anyone suggest me where I can store the images which is easy to use in my app. I mean should I store it locally or in cloud? If yes which cloud or backend should I use, whichone is good and fully optimized for my flutter app (like mongo, django, firebase etc. ). Will anyone suggest me the best?
Anyone kind of help is appreaciated as I have no prior knowledge about the production part....
Storing Images on a server can be very expensive, since the file sizes are very large compared to the usual data. So if you do not NEED to store them on a server, don't.
Storing images locally is pretty simple. You will want to use the path_provider package https://pub.dev/packages/path_provider . I ll post a function I am using in my current project that does this. You ll see, its pretty simple.
Note: In my Code I pull the file from my server. Obviously leave that part out if you are getting your images from a different source.
Future<File> createFileOfPdfUrl(String fileLocation, String name) async {
final url = Helper.baseUrl + "Files/Newsletter/" + fileLocation;
final filename = url.substring(url.lastIndexOf("/") + 1);
var request = await HttpClient().getUrl(Uri.parse(url));
var response = await request.close();
var bytes = await consolidateHttpClientResponseBytes(response);
String dir = (await pathProvider.getApplicationDocumentsDirectory()).path;
File file = new File('$dir/$filename');
await file.writeAsBytes(bytes);
return file;
}
I have a sales app develpmented in Flex Builder. For use photos by off-line way, i upload a compressed file with all photos to the site and when need i sincronize with my smartphone. In that process is made a download to the dispositive and exist a responsable plugin to descompress the archive and disponibilize it in apropriate folder to later use.
That compressed file has 500MB size - 6700 photos approximately - and in Flex i have no type of problem to do that.
I'm rewriting the app in Flutter, using a archive package, dont getting the same results. In the descompress process i have problem with Out of memory.
Somebody already faced for something like that ?
Is there an best way to do this ?
I already tried other two alternatives:
- To use the Image.network, but, one of requires is work off-line.
- To save all the photos in assets folder, but i think that is not the best alternative, because the app will get bigger
Thank you in advance for.
Follow the error message and the code
code:
unarchiveAndSave()async{
var zippedFile = await initDir();
var bytes = zippedFile.readAsBytesSync();
var archive = ZipDecoder().decodeBytes(bytes);
for (var file in archive) {
var fileName = '$_dir/${file.name}';
if (file.isFile) {
var outFile = File(fileName);
print('File:: ${outFile.path}');
outFile = await outFile.create();
await outFile.writeAsBytes(file.content);
}
}
print('terminei de descompactar os arquivos');
}
I'm trying to compress image from camera or gallery, but i tried answer in this question Flutter & Firebase: Compression before upload image
But the UI was freeze , so do you guys have any solution for that, and why the image plugin meet that problem ?
UPDATE:
compressImage(imageFile).then((File file) {
imageFile = file;
});
Future<File> compressImage(File imageFile) async {
return compute(decodeImage, imageFile);
}
File decodeImage(File imageFile) {
Im.Image image = Im.decodeImage(imageFile.readAsBytesSync());
Im.Image smallerImage = Im.copyResize(
image, 150); // choose the size here, it will maintain aspect ratio
return new File('123.jpg')
..writeAsBytesSync(Im.encodeJpg(smallerImage, quality: 85));
}
I meet "unhandled exception" in this code
This is because compression is done in the UI thread.
You can move computation to a new thread using compute() https://docs.flutter.io/flutter/foundation/compute.html
There are currently serious limitations what a non-UI thread can do.
If you pass the image data, it is copied from one thread to the other, which can be slow. If you have the image in a file like you get it from image_picker it is better to pass the file path and read the image in the new thread.
You can only pass values that can be encoded as JSON (it's not actually encoded as JSON, but it supports the same types)
You can not use plugins. This means you need to move the compressed data back to the UI thread by passing the data (which again is copied) or by writing in a file and passing back the path to the file, but in this case copying might be faster because writing a file in one thread and reading it in the other is even slower).
Then you can for example invoke image uploading to Firebase Cloud Storage in the UI thread, but because this is a plugin it will run in native code and not in the UI thread. It's just the UI thread that needs to pass the image along.
I'm building an App with actionscript 3.0 in my Flash builder. This is a followup question this question.
I need to upload the bytearray to my server, but the function i use to convert the bitmapdata to a ByteArray is super slow, so slow it freezes up my mobile device. My code is as follows:
var jpgenc:JPEGEncoder = new JPEGEncoder(50);
trace('encode');
//encode the bitmapdata object and keep the encoded ByteArray
var imgByteArray:ByteArray = jpgenc.encode(bitmap);
temp2 = File.applicationStorageDirectory.resolvePath("snapshot.jpg");
var fs:FileStream = new FileStream();
trace('fs');
try{
//open file in write mode
fs.open(temp2,FileMode.WRITE);
//write bytes from the byte array
fs.writeBytes(imgByteArray);
//close the file
fs.close();
}catch(e:Error){
Is there a different way to convert it to a byteArray? Is there a better way?
Try to use blooddy library: http://www.blooddy.by . But i didn't test it on mobile devices. Comment if you will have success.
Use BitmapData.encode(), it's faster by orders of magnitude on mobile http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/BitmapData.html#encode%28%29
You should try to find a JPEG encoder that is capable of encoding asynchronously. That way the app can still be used while the image is being compressed. I haven't tried any of the libraries, but this one looks promising:
http://segfaultlabs.com/devlogs/alchemy-asynchronous-jpeg-encoding-2
It uses Alchemy, which should make it faster than the JPEGEncoder from as3corelib (which I guess is the one you're using at the moment.)
A native JPEG encoder is ideal, asynchronous would be good, but possibly still slow (just not blocking). Another option:
var pixels:ByteArray = bitmapData.getPixels(bitmapData.rect);
pixels.compress();
I'm not sure of native performance, and performance definitely depends on what kind of images you have.
The answer from Ilya was what did it for me. I downloaded the library and there is an example of how to use it inside. I have been working on getting the CameraUI in flashbuilder to take a picture, encode / compress it, then send it over via a web service to my server (the data was sent as a compressed byte array). I did this:
by.blooddy.crypto.image.JPEGEncoder.encode( bmp, 30 );
Where bmp is my bitmap data. The encode took under 3 seconds and was easily able to fit into my flow of control synchronously. I tried async methods but they ultimately took a really long time and were difficult to track for things like when a user moved from cell service to wifi or from tower to tower while an upload was going on.
Comment here if you need more details.