use same algo for avatar placeholder

src/main/java/com/owncloud/android/ui/TextDrawable.java

@@ -113,10 +113,10 @@ public class TextDrawable extends Drawable {
     @NonNull
     public static TextDrawable createNamedAvatar(String name, float radiusInDp) throws
             UnsupportedEncodingException, NoSuchAlgorithmException {
-        int[] rgb = BitmapUtils.calculateRGB(name);
-        TextDrawable avatar = new TextDrawable(
-                name.substring(0, 1).toUpperCase(), rgb[0], rgb[1], rgb[2], radiusInDp);
-        return avatar;
+        int[] hsl = BitmapUtils.calculateHSL(name);
+        int[] rgb = BitmapUtils.HSLtoRGB(hsl[0], hsl[1], hsl[2], 1);
+
+        return new TextDrawable(name.substring(0, 1).toUpperCase(), rgb[0], rgb[1], rgb[2], radiusInDp);
     }
 
     /**

src/main/java/com/owncloud/android/utils/BitmapUtils.java

@@ -29,16 +29,17 @@ import android.support.v4.graphics.drawable.RoundedBitmapDrawableFactory;
 
 import com.owncloud.android.lib.common.utils.Log_OC;
 
+import org.apache.commons.codec.binary.Hex;
+
 import java.io.UnsupportedEncodingException;
-import java.math.BigInteger;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
-import java.util.Locale;
 
 /**
  * Utility class with methods for decoding Bitmaps.
  */
 public class BitmapUtils {
+    public static final String TAG = BitmapUtils.class.getSimpleName();
 
 
     /**
@@ -188,7 +189,7 @@ public class BitmapUtils {
      *
      *  @param h Hue is specified as degrees in the range 0 - 360.
      *  @param s Saturation is specified as a percentage in the range 1 - 100.
-     *  @param l Lumanance is specified as a percentage in the range 1 - 100.
+     *  @param l Luminance is specified as a percentage in the range 1 - 100.
      *  @param alpha  the alpha value between 0 - 1
      *  adapted from https://svn.codehaus.org/griffon/builders/gfxbuilder/tags/GFXBUILDER_0.2/
      *  gfxbuilder-core/src/main/com/camick/awt/HSLColor.java
@@ -267,17 +268,98 @@ public class BitmapUtils {
      * @throws UnsupportedEncodingException if the charset is not supported
      * @throws NoSuchAlgorithmException if the specified algorithm is not available
      */
-    public static int[] calculateRGB(String name) throws UnsupportedEncodingException, NoSuchAlgorithmException {
-        // using adapted algorithm from /core/js/placeholder.js:50
-        byte[] seed = name.getBytes("UTF-8");
-        MessageDigest md = MessageDigest.getInstance("MD5");
-        Integer seedMd5Int = String.format(Locale.ROOT, "%032x",
-                new BigInteger(1, md.digest(seed))).hashCode();
+    public static int[] calculateHSL(String name) throws UnsupportedEncodingException, NoSuchAlgorithmException {
+        // using adapted algorithm from https://github.com/nextcloud/server/blob/master/core/js/placeholder.js#L126
+
+        String[] result = new String[]{"0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0"};
+        double[] rgb = new double[]{0, 0, 0};
+        int sat = 70;
+        int lum = 68;
+        int modulo = 16;
+
+        String hash = name.toLowerCase().replaceAll("[^0-9a-f]", "");
+
+        if (!hash.matches("^[0-9a-f]{32}")) {
+            hash = md5(hash);
+        }
+
+        // Splitting evenly the string
+        for (int i = 0; i < hash.length(); i++) {
+            result[i % modulo] = result[i % modulo] + String.valueOf(Integer.parseInt(hash.substring(i, i + 1), 16));
+        }
 
-        double maxRange = Integer.MAX_VALUE;
-        float hue = (float) (seedMd5Int / maxRange * 360);
+        // Converting our data into a usable rgb format
+        // Start at 1 because 16%3=1 but 15%3=0 and makes the repartition even
+        for (int count = 1; count < modulo; count++) {
+            rgb[count % 3] += (Integer.parseInt(result[count]));
+        }
+
+        // Reduce values bigger than rgb requirements
+        rgb[0] = rgb[0] % 255;
+        rgb[1] = rgb[1] % 255;
+        rgb[2] = rgb[2] % 255;
+
+        double[] hsl = rgbToHsl(rgb[0], rgb[1], rgb[2]);
+
+        // Classic formula to check the brightness for our eye
+        // If too bright, lower the sat
+        double bright = Math.sqrt(0.299 * Math.pow(rgb[0], 2) + 0.587 * Math.pow(rgb[1], 2) + 0.114
+                * Math.pow(rgb[2], 2));
+
+        if (bright >= 200) {
+            sat = 60;
+        }
+
+        return new int[]{(int) (hsl[0] * 360), sat, lum};
+    }
+
+    private static double[] rgbToHsl(double r, double g, double b) {
+        r /= 255;
+        g /= 255;
+        b /= 255;
+
+        double max = Math.max(r, Math.max(g, b));
+        double min = Math.min(r, Math.min(g, b));
+        double h = (max + min) / 2;
+        double s;
+        double l = (max + min) / 2;
+
+        if (max == min) {
+            h = s = 0; // achromatic
+        } else {
+            double d = max - min;
+            s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
+
+            if (max == r) {
+                h = (g - b) / d + (g < b ? 6 : 0);
+            } else if (max == g) {
+                h = (b - r) / d + 2;
+            } else if (max == b) {
+                h = (r - g) / d + 4;
+            }
+            h /= 6;
+        }
+
+        double[] hsl = new double[]{0.0, 0.0, 0.0};
+        hsl[0] = h;
+        hsl[1] = s;
+        hsl[2] = l;
+
+        return hsl;
+    }
+
+    public static String md5(String string) {
+        try {
+            MessageDigest md5 = MessageDigest.getInstance("MD5");
+            md5.update(string.getBytes());
+
+            return new String(Hex.encodeHex(md5.digest()));
+
+        } catch (Exception e) {
+            Log_OC.e(TAG, e.getMessage());
+        }
 
-        return BitmapUtils.HSLtoRGB(hue, 90.0f, 65.0f, 1.0f);
+        return "";
     }
 
     /**