ContactImageConverter.cs

using System;
using System.Globalization;
using Android.Graphics;
using Android.Graphics.Drawables;
using Cirrious.CrossCore.Converters;
using DecisionBuddy.Controls;
using DecisionBuddy.Controls.Utils;
using DecisionBuddy.Core.Model;

namespace DecisionBuddy.UI.Droid.Converters
{
    public class ContactImageConverter : MvxValueConverter<Contact, Bitmap>
    {
        private const int DEFAULT_SIZE = 50;

        protected override Bitmap Convert(Contact value, Type targetType, object parameter, CultureInfo culture)
        {
            if(value == null) return null;

            if (value.Thumbnail != null && value.Thumbnail.Length > 0)
            {
                return BitmapFactory.DecodeByteArray(value.Thumbnail, 0, value.Thumbnail.Length);
            }
            
            var size = DEFAULT_SIZE;
            if (parameter is long || parameter is int)
                size = System.Convert.ToInt32(parameter);

            var canvas = new Canvas();
            var letter = value.Name.Trim().Substring(0,1);
            var textDrawable = TextDrawable
                                        .Builder()
                                        .BeginConfig()
                                        .SetHeight(size)
                                        .SetWidth(size)
                                        .EndConfig()
                                        .BuildRound(letter, ColorGenerator.Material.GetColor(letter));

            return DrawableToBitmap(textDrawable);
        }

        protected override Contact ConvertBack(Bitmap value, Type targetType, object parameter, CultureInfo culture)
        {
            //var stream = new MemoryStream();
            //value.Compress(Bitmap.CompressFormat.Jpeg, 100, stream);
            //return stream.ToArray();
            return null;
        }

        public static Bitmap DrawableToBitmap(Drawable drawable)
        {
            Bitmap bitmap = null;

            var bitmapDrawable = drawable as BitmapDrawable;
            if (bitmapDrawable?.Bitmap != null)
            {
                return bitmapDrawable.Bitmap;
            }

            if (drawable.IntrinsicWidth <= 0 || drawable.IntrinsicHeight <= 0)
            {
                bitmap = Bitmap.CreateBitmap(1, 1, Bitmap.Config.Argb8888); // Single color bitmap will be created of 1x1 pixel
            }
            else
            {
                bitmap = Bitmap.CreateBitmap(drawable.IntrinsicWidth, drawable.IntrinsicHeight, Bitmap.Config.Argb8888);
            }

            var canvas = new Canvas(bitmap);
            drawable.SetBounds(0, 0, canvas.Width, canvas.Height);
            drawable.Draw(canvas);
            return bitmap;
        }

    }
}