Identicon generation code from Android-Identicons

Source: https://github.com/saiimons/Android-Identicons
License: Apache License, Version 2.0

briar-android/src/im/delight/android/identicons/IdenticonBase.java

@@ -0,0 +1,120 @@
+package im.delight.android.identicons;
+
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+
+import java.security.MessageDigest;
+
+/**
+ * Created by saiimons on 05/10/14.
+ */
+public abstract class IdenticonBase {
+    private static final String HASH_ALGORITHM = "SHA-256";
+
+
+    private final int mRowCount;
+    private final int mColumnCount;
+    private final Paint mPaint;
+    private volatile int mCellWidth;
+    private volatile int mCellHeight;
+    private volatile byte[] mHash;
+    private volatile int[][] mColors;
+    private volatile boolean mReady;
+
+    public IdenticonBase() {
+        mRowCount = getRowCount();
+        mColumnCount = getColumnCount();
+        mPaint = new Paint();
+
+        mPaint.setStyle(Paint.Style.FILL);
+        mPaint.setAntiAlias(true);
+        mPaint.setDither(true);
+    }
+
+    public static byte[] getHash(String input) {
+        byte[] mHash;
+        // if the input was null
+        if (input == null) {
+            // we can't create a hash value and have nothing to show (draw to the view)
+            mHash = null;
+        }
+        // if the input was a proper string (non-null)
+        else {
+            // generate a hash from the string to get unique but deterministic byte values
+            try {
+                final MessageDigest digest = java.security.MessageDigest.getInstance(HASH_ALGORITHM);
+                digest.update(input == null ? new byte[0] : input.getBytes());
+                mHash = digest.digest();
+            } catch (Exception e) {
+                mHash = null;
+            }
+        }
+        return mHash;
+    }
+
+    protected void setupColors() {
+        mColors = new int[mRowCount][mColumnCount];
+        int colorVisible = getIconColor();
+
+        for (int r = 0; r < mRowCount; r++) {
+            for (int c = 0; c < mColumnCount; c++) {
+                if (isCellVisible(r, c)) {
+                    mColors[r][c] = colorVisible;
+                } else {
+                    mColors[r][c] = Color.TRANSPARENT;
+                }
+            }
+        }
+    }
+
+    public void show(String input) {
+        if(input != null) {
+            mHash = IdenticonBase.getHash(input);
+        } else {
+            mHash = null;
+        }
+        // set up the cell colors according to the input that was provided via show(...)
+        setupColors();
+
+        // this view may now be drawn (and thus must be re-drawn)
+        mReady = true;
+    }
+
+    public byte getByte(int index) {
+        if (mHash == null) {
+            return -128;
+        } else {
+            return mHash[index % mHash.length];
+        }
+    }
+
+    abstract protected int getRowCount();
+
+    abstract protected int getColumnCount();
+
+    abstract protected boolean isCellVisible(int row, int column);
+
+    abstract protected int getIconColor();
+
+    public void updateSize(int w, int h) {
+        mCellWidth = w / mColumnCount;
+        mCellHeight = h / mRowCount;
+    }
+
+    protected void draw(Canvas canvas) {
+        if (mReady) {
+            int x, y;
+            for (int r = 0; r < mRowCount; r++) {
+                for (int c = 0; c < mColumnCount; c++) {
+                    x = mCellWidth * c;
+                    y = mCellHeight * r;
+
+                    mPaint.setColor(mColors[r][c]);
+
+                    canvas.drawRect(x, y + mCellHeight, x + mCellWidth, y, mPaint);
+                }
+            }
+        }
+    }
+}