Added identicons

app/src/main/java/eu/faircode/email/Identicon.java

@@ -0,0 +1,42 @@
+package eu.faircode.email;
+
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.RectF;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+class Identicon {
+    static Bitmap generate(String email, int size, int pixels) {
+        byte[] hash;
+        try {
+            hash = MessageDigest.getInstance("MD5").digest(email.getBytes());
+        } catch (NoSuchAlgorithmException ignored) {
+            hash = email.getBytes();
+        }
+
+        Paint paint = new Paint();
+        paint.setColor(Color.argb(255, hash[0], hash[1], hash[2]));
+
+        Bitmap bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
+        Canvas canvas = new Canvas(bitmap);
+        canvas.drawColor(Color.argb(255, 128, 128, 128));
+
+        float psize = (float) size / pixels;
+
+        for (int x = 0; x < pixels; x++) {
+            int i = (x > pixels / 2 ? pixels - x - 1 : x);
+            for (int y = 0; y < pixels; y++) {
+                if ((hash[i] >> y & 1) == 1) {
+                    RectF rect = new RectF(x * psize, y * psize, (x + 1) * psize, (y + 1) * psize);
+                    canvas.drawRect(rect, paint);
+                }
+            }
+        }
+
+        return bitmap;
+    }
+}