Develop Reference

How to create an image out of a custom control in Xamarin Forms? [duplicate]

Is there a package that does screen capture in xamarin.forms ?
I need also to capture google maps screen shots

Check out this blog post by Daniel Hindrikes.
I'm going to assume that you use a PCL for your shared code.
You will need to create an interface in your PCL. He calls it IScreenshotManager. The declaration looks like this:
public interface IScreenshotManager
{
Task<byte[]> CaptureAsync();
}
Now all platforms will have their own implementation for it.
For iOS;
public class ScreenshotManager : IScreenshotManager
{
public async System.Threading.Tasks.Task<byte[]> CaptureAsync()
{
var view = UIApplication.SharedApplication.KeyWindow.RootViewController.View;
UIGraphics.BeginImageContext(view.Frame.Size);
view.DrawViewHierarchy(view.Frame, true);
var image = UIGraphics.GetImageFromCurrentImageContext();
UIGraphics.EndImageContext();
using(var imageData = image.AsPNG())
{
var bytes = new byte[imageData.Length];
System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, bytes, 0, Convert.ToInt32(imageData.Length));
return bytes;
}
}
}
For Android:
public class ScreenshotManager : IScreenshotManager
{
public static Activity Activity { get; set; }
public async System.Threading.Tasks.Task<byte[]> CaptureAsync()
{
if(Activity == null)
{
throw new Exception("You have to set ScreenshotManager.Activity in your Android project");
}
var view = Activity.Window.DecorView;
view.DrawingCacheEnabled = true;
Bitmap bitmap = view.GetDrawingCache(true);
byte[] bitmapData;
using (var stream = new MemoryStream())
{
bitmap.Compress(Bitmap.CompressFormat.Png, 0, stream);
bitmapData = stream.ToArray();
}
return bitmapData;
}
}
And for Windows Phone:
public class ScreenshotManager : IScreenshotManager
{
public async Task<byte[]> CaptureAsync()
{
var rootFrame = Application.Current.RootVisual as PhoneApplicationFrame;
var screenImage = new WriteableBitmap((int)rootFrame.ActualWidth, (int)rootFrame.ActualHeight);
screenImage.Render(rootFrame, new MatrixTransform());
screenImage.Invalidate();
using (var stream = new MemoryStream())
{
screenImage.SaveJpeg(stream, screenImage.PixelWidth, screenImage.PixelHeight, 0, 100);
var bytes = stream.ToArray();
return bytes;
}
}
}
Don't forget to register your platform specific implementations with the attribute which registers it with the Dependency Service, like this:
[assembly: Xamarin.Forms.Dependency (typeof (ScreenshotManager))]
It goes above the namespace declaration.
Now from your shared code you would be able to get the byte[] of a screenshot with a call like this:
var screenshotBytes = DependencyService.Get<IScreenshotManager>().CaptureAsync();
You probably want to check if DependencyService.Get<IScreenshotManager>() isn't null before using it.
After that you can turn your byte[] into an image and do whatever you like with it!

Implementation for UWP
public async Task<byte[]> CaptureAsync()
{
//create and capture Window
var renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(Window.Current.Content);
var pixelpuffer = await renderTargetBitmap.GetPixelsAsync();
var logicalDpi = DisplayInformation.GetForCurrentView().LogicalDpi;
IRandomAccessStream stream = new InMemoryRandomAccessStream();
BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, stream);
encoder.BitmapTransform.InterpolationMode = BitmapInterpolationMode.Fant;
encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, (uint)renderTargetBitmap.PixelWidth, (uint)renderTargetBitmap.PixelHeight, logicalDpi, logicalDpi, pixelpuffer.ToArray());
await encoder.FlushAsync();
byte[] resultingBuffer = new byte[stream.Size];
await stream.ReadAsync(resultingBuffer.AsBuffer(), (uint)resultingBuffer.Length, InputStreamOptions.None);
return resultingBuffer;
}

Picking and assigning image

I'm trying to make an app like contact app,but I can't figure out how to assign image to the contact from inside the app using image picker and save the changes in a SQLite database.
I'm developing this using xamarin forms
I have an interface
public interface IPhotoPickerService
{
Task<Stream> GetImageStreamAsync();
}
and in my android implementation
[assembly: Dependency(typeof(PhotoPickerService))]
namespace Drugs.Droid.Sevices
{
public class PhotoPickerService : IPhotoPickerService
{
public Task<Stream> GetImageStreamAsync()
{
// Define the Intent for getting images
Intent intent = new Intent();
intent.SetType("image/*");
intent.SetAction(Intent.ActionGetContent);
// Start the picture-picker activity (resumes in MainActivity.cs)
MainActivity.Instance.StartActivityForResult(
Intent.CreateChooser(intent, "Select Photo"),
MainActivity.PickImageId);
// Save the TaskCompletionSource object as a MainActivity property
MainActivity.Instance.PickImageTaskCompletionSource = new TaskCompletionSource<Stream>();
// Return Task object
return MainActivity.Instance.PickImageTaskCompletionSource.Task;
}
}
}
and then when I try to save the image after i picked it up
by this method
async void OnPickPhotoButtonClicked(object sender, EventArgs e)
{
var drug = (Drug)BindingContext;
(sender as Button).IsEnabled = false;
Stream stream = await DependencyService.Get<IPhotoPickerService>().GetImageStreamAsync();
if (stream != null)
{
image.Source = ImageSource.FromStream(() => stream);
}
(sender as Button).IsEnabled = true;
}
how can i save the image I'm getting from stream to a sqlite database or a local folder

Agree with #Jason .If you want to picker image from device and save it to DB . You could use the plugin Xam.Plugin.Media from nuget .
Usage
async void OnPickPhotoButtonClicked(object sender, EventArgs e)
{
await CrossMedia.Current.Initialize();
if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
{
return;
}
var file = await CrossMedia.Current.PickPhotoAsync();
if (file == null)
return;
image.Source = ImageSource.FromStream(() =>
{
var stream = file.GetStream();
return stream;
});
And you should convert the stream to Byte array so that you save them to sqlite.
public byte[] GetImageStreamAsBytes(Stream input)
{
var buffer = new byte[16*1024];
using (MemoryStream ms = new MemoryStream())
{
int read;
while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
{
ms.Write(buffer, 0, read);
}
return ms.ToArray();
}
}
var imgDate = GetImageStreamAsBytes(file.GetStream());
For more details about the plugin you could check https://github.com/jamesmontemagno/MediaPlugin .

How can I add an image in my database sqlite using dbContext WPF c#?

I want to add an image to the database in an image column in byte form
I am using SQLite to save my database data and WPF Application using dbContext c# to write my code
can anyone help me please?
private void ChooseImageButtonClick(object sender, RoutedEventArgs e)
{
Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
dlg.Filter = "Choose Image(*.JPG;*.PNG;*.GIF)|*.jpg;*.png;*.gif";
if (dlg.ShowDialog() == true)
{
string FileName = dlg.FileName.ToString();
BitmapImage bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.UriSource = new Uri(FileName);
bitmap.EndInit();
ImageBox.Source = bitmap;
}
}
private void savebtnClick(object sender, RoutedEventArgs e)
{
using (DatabaseContext dbContext = new DatabaseContext())
{
Person p = new Person
{
Id = int.Parse(Idtextbox.Text),
Name = Nametextbox.Text,
Image = image
};
dbContext.Person.Add(p);
dbContext.SaveChanges();
RefreshList();
}
}

Just convert BitmapImage to byte array first
byte[] image;
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
encoder.QualityLevel = 100;
using (MemoryStream ms = new MemoryStream())
{
encoder.Frames.Add(BitmapFrame.Create((BitmapSource)ImageBox.Source));
encoder.Save(ms);
image = ms.ToArray();
}
encoder = null;
And in your database context - add
using (DatabaseContext dbContext = new DatabaseContext())
{
Part part = new Part();
part.Id = int.Parse(TextBoxID.Text);
part.Name = TextBoxName.Text;
part.Image = image;
dbContext.Part.Add(part);
dbContext.SaveChanges();
RefreshPartsList();
}}
To convert byte array back to BitmapImage :
byte[] imageData = part.Image; // that you get from db
if (imageData == null || imageData.Length == 0)
{
//Show error msg or return here;
return;
}
var image = new BitmapImage();
using (var ms = new System.IO.MemoryStream(imageData))
{
image.BeginInit();
image.CacheOption = BitmapCacheOption.OnLoad;
image.StreamSource = ms;
image.EndInit();
image.Freeze();
}

Add Property in 'Part' class
public byte[] ImageCol { get; set; }
Then from "OpenFileDialog" create Image from selected file. For Example
OpenFileDialog openFileDialog = new OpenFileDialog
{
Filter = "Image Files(*.BMP;*.JPG;*.JPEG;*.GIF;*.PNG)|*.BMP;*.JPG;*.JPEG;*.GIF;*.PNG",
InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
};
if (openFileDialog.ShowDialog()==DialogResult.OK)
{
var imageFromFile = System.Drawing.Image.FromFile(openFileDialog.FileName);
part.ImageCol = imageFromFile.ConvertBitmapImagetoBytes();
}
Convert BitMap to byte[]
public static byte[] ConvertBitmapImagetoBytes(this Image image)
{
MemoryStream ms = new MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
return ms.ToArray();
}

Load image from url to ImageView - C#

I want to load an image from url to imageview in c# ( android programming ) after search in google i cant find any good result , thank you for helping
i am using xamarin studio

The very first hit I got from Google was a thread on the Xamarin forums discussing this exact issue:
private Bitmap GetImageBitmapFromUrl(string url)
{
Bitmap imageBitmap = null;
using (var webClient = new WebClient())
{
var imageBytes = webClient.DownloadData(url);
if (imageBytes != null && imageBytes.Length > 0)
{
imageBitmap = BitmapFactory.DecodeByteArray(imageBytes, 0, imageBytes.Length);
}
}
return imageBitmap;
}
var imageBitmap = GetImageBitmapFromUrl("http://xamarin.com/resources/design/home/devices.png");
imagen.SetImageBitmap(imageBitmap);

Both approaches work, but is a good practice to do it asynchronously. Here you have some good examples:
Asynchronous Image Loading in Xamarin Android http://javatechig.com/xamarin/asynchronous-image-loading-xamarin-android
xamarin-store-app image helper https://github.com/xamarin/xamarin-store-app/blob/master/XamarinStore.Droid/Helpers/Images.cs

Am using the below class in Xamarin Android:
public class DownloadImageTask : AsyncTask
{
private ImageView bmImage;
private ProgressBar progressBar;
public DownloadImageTask( ImageView bmImage , ProgressBar progressBar)
{
this.bmImage = bmImage;
this.progressBar = progressBar;
}
protected override void OnPostExecute( Object result )
{
base.OnPostExecute(result);
bmImage.SetImageBitmap(( Bitmap ) result);
if (progressBar != null)
progressBar.Visibility = ViewStates.Gone;
}
protected override Object DoInBackground( params Object[] #params )
{
var urldisplay = #params[0].ToString();
Bitmap mIcon11 = null;
try
{
var req = WebRequest.Create(urldisplay);
var response = req.GetResponse();
var stream = response.GetResponseStream();
mIcon11 = BitmapFactory.DecodeStream(stream);
}
catch ( Exception e )
{
}
return mIcon11;
}
}
Execution :
new DownloadImageTask(imgProfile , progressBar).Execute(uri);

I did this to load an Svg from an url into an ImageView using SkiaSharp.
In the .xml
<ImageView
android:contentDescription=""
android:id="#+id/video_recorder_image"
android:layout_width="wrap_content"
android:layout_height="50dp" />
In the activity/fragment.
private ImageView iconImageView;
public override void OnViewCreated(View view, Bundle savedInstanceState)
{
iconImageView = (ImageView)view.FindViewById(Resource.Id.video_recorder_image);
Bitmap image = GetImageBitmapFromUrl(_iconUrl);
}
private Bitmap GetImageBitmapFromUrl(string url)
{
Bitmap imageBitmap = null;
using (var webClient = new WebClient())
{
var imageBytes = webClient.DownloadData(url);
if (imageBytes != null && imageBytes.Length > 0)
{
var svgContent = Convert.ToBase64String(imageBytes, 0, imageBytes.Length);
var byteArray = Convert.FromBase64String(svgContent);
using (var stream = new MemoryStream(byteArray))
{
var bitmap = new SKBitmap(500, 500);
var canvas = new SKCanvas(bitmap);
// load the SVG
var svg = new SkiaSharp.Extended.Svg.SKSvg(new SKSize(500, 500));
svg.Load(stream);
// draw the SVG to the bitmap
canvas.DrawPicture(svg.Picture);
var skData = SKImage.FromBitmap(bitmap).Encode(SKEncodedImageFormat.Png, 100);
// Convert image to string and then to Bitmap
var convertedSvgStream = skData.AsStream();
var convertedImageBytes = new byte[(int)convertedSvgStream.Length];
convertedSvgStream.Seek(0, SeekOrigin.Begin);
convertedSvgStream.Read(convertedImageBytes, 0, (int)convertedSvgStream.Length);
imageBitmap = BitmapFactory.DecodeByteArray(convertedImageBytes, 0, convertedImageBytes.Length);
}
}
}
return imageBitmap;
}

Downloading image from web asychrounly in parallel ForEach loop

Hi I would like download images from web asychrounly in parallel loop foreach.
I have dictionary with signature IDictionary<string,user>.
User class has two properties:
Uri ProfilePhoto
BitmapImage ProfilePhotoAsBitmapImage
My aim is, go through dictionary in loop if ProfilePhoto is null I get default avatar, it not I would like download image from web asynchronly.
private void GetProfilePhotosFromServer(IEnumerable<UserInfo> friends)
{
Parallel.ForEach(friends, f =>
{
//get defualt
if (f.ProfilePhoto == null)
f.ProfilePhotoAsBitmap = CreateDefaultAvatar(f.Sex);
//start downloading from web server asynchronly
//problem is that I don’t know how retrieve BitmapImage object from
//StartDownloading method or method ProcessImage, which is on the bottom
//of my question
var image = StartDownloadingImage(f.MediumProfilePhoto);
image.Freeze();
f.ProfilePhotoAsBitmap = image;
});
}
Problem is that I don’t know how retrieve BitmapImage object from StartDownloading method or method ProcessImage, which is on the bottom of my question.
Start web request:
private void StartDownloadingImage(Uri imageUri)
{
_webRequest = WebRequest.Create(imageUri);
_webRequest.BeginGetResponse(this.ProcessImage, null);
//how retrieve result of ProcessImage method
}
After web request is finished I call this method:
private void ProcessImage(IAsyncResult asyncResult)
{
var response = _webRequest.EndGetResponse(asyncResult);
using (var stream = response.GetResponseStream())
{
var buffer = new Byte[response.ContentLength];
int offset = 0, actuallyRead = 0;
do
{
actuallyRead = stream.Read(buffer, offset, buffer.Length - offset);
offset += actuallyRead;
}
while (actuallyRead > 0);
var image = new BitmapImage
{
CreateOptions = BitmapCreateOptions.None,
CacheOption = BitmapCacheOption.OnLoad
};
image.BeginInit();
image.StreamSource = new MemoryStream(buffer);
image.EndInit();
//problem
return image;
}
}
BitmapImage object is created in ProcessImage method how can I pass this object to the property od User object which is used in GetProfilePhotosFromServer method?
Method above create from MemoryStream BitampImage object.

You need to pass in the additional operations and the UserInfo object as a callback to the asynchronous method. The easiest way to do this is to create a class containing them and pass that as the asynchronous state of the method.
private class ImageCallbackState
{
public UserInfo Friend { get; set; }
public Action<UserInfo,BitmapImage> Callback { get; set; }
}
private void GetProfilePhotosFromServer(IEnumerable<UserInfo> friends)
{
Parallel.ForEach(friends, f =>
{
//get defualt
if (f.ProfilePhoto == null)
f.ProfilePhotoAsBitmap = CreateDefaultAvatar(f.Sex);
Action<UserInfo,BitmapImage> action = (u,i) => {
i.Freeze();
u.ProfilePhotoAsBitMap = i;
};
var state = new ImageCallbackState { Friend = f, Callback = action };
StartDownloadingImage(f.MediumProfilePhoto,state);
});
}
private void StartDownloadingImage(Uri imageUri, ImageCallbackState state)
{
_webRequest = WebRequest.Create(imageUri);
_webRequest.BeginGetResponse(this.ProcessImage, state); // pass callback state
}
private void ProcessImage(IAsyncResult asyncResult)
{
var response = _webRequest.EndGetResponse(asyncResult);
using (var stream = response.GetResponseStream())
{
var buffer = new Byte[response.ContentLength];
int offset = 0, actuallyRead = 0;
do
{
actuallyRead = stream.Read(buffer, offset, buffer.Length - offset);
offset += actuallyRead;
}
while (actuallyRead > 0);
var image = new BitmapImage
{
CreateOptions = BitmapCreateOptions.None,
CacheOption = BitmapCacheOption.OnLoad
};
image.BeginInit();
image.StreamSource = new MemoryStream(buffer);
image.EndInit();
var state = asyncResult.AsyncState as ImageCallbackState
state.Callback(state.Friend,image);
}
}