fix "rough scaling" bitmaps

Fixes #3347
Closes #3408
// FREEBIE

src/org/thoughtcrime/securesms/util/BitmapUtil.java

@@ -133,17 +133,11 @@ public class BitmapUtil {
     final int imageWidth  = options.outWidth;
     final int imageHeight = options.outHeight;
 
-    int scaler = 1;
-    int scaleFactor = (constrainedMemory ? 1 : 2);
-    while ((imageWidth / scaler / scaleFactor >= maxWidth) && (imageHeight / scaler / scaleFactor >= maxHeight)) {
-      scaler *= 2;
-    }
-
-    options.inSampleSize       = scaler;
+    options.inSampleSize       = getScaleFactor(imageWidth, imageHeight, maxWidth, maxHeight, constrainedMemory);
     options.inJustDecodeBounds = false;
 
-    BufferedInputStream is = new BufferedInputStream(data);
-    Bitmap roughThumbnail  = BitmapFactory.decodeStream(is, null, options);
+    InputStream is             = new BufferedInputStream(data);
+    Bitmap      roughThumbnail = BitmapFactory.decodeStream(is, null, options);
     try {
       is.close();
     } catch (IOException ioe) {
@@ -189,6 +183,20 @@ public class BitmapUtil {
     }
   }
 
+  @VisibleForTesting static int getScaleFactor(int inWidth, int inHeight,
+                                               int maxWidth, int maxHeight,
+                                               boolean constrained)
+  {
+    int scaler = 1;
+    while (!constrained && ((inWidth / scaler / 2 >= maxWidth) && (inHeight / scaler / 2 >= maxHeight))) {
+      scaler *= 2;
+    }
+    while (constrained && ((inWidth / scaler > maxWidth) || (inHeight / scaler > maxHeight))) {
+      scaler *= 2;
+    }
+    return scaler;
+  }
+
   private static Bitmap fixOrientation(Bitmap bitmap, InputStream orientationStream) {
     final int orientation = Exif.getOrientation(orientationStream);
 

test/androidTest/java/org/thoughtcrime/securesms/util/BitmapUtilTest.java

@@ -0,0 +1,34 @@
+package org.thoughtcrime.securesms.util;
+
+import org.thoughtcrime.securesms.TextSecureTestCase;
+
+public class BitmapUtilTest extends TextSecureTestCase {
+  public void testScaleFactorNormal() {
+    assertEquals(1, BitmapUtil.getScaleFactor(1000, 1000, 9000, 9000, false));
+
+    assertEquals(1, BitmapUtil.getScaleFactor(1000, 1000, 750, 750, false));
+    assertEquals(2, BitmapUtil.getScaleFactor(1000, 1000, 500, 500, false));
+    assertEquals(2, BitmapUtil.getScaleFactor(1000, 1000, 499, 499, false));
+    assertEquals(4, BitmapUtil.getScaleFactor(1000, 1000, 250, 250, false));
+    assertEquals(4, BitmapUtil.getScaleFactor(1000, 1000, 249, 249, false));
+
+    assertEquals(1, BitmapUtil.getScaleFactor(1000, 500, 750, 750, false));
+    assertEquals(1, BitmapUtil.getScaleFactor(2000, 1000, 501, 501, false));
+    assertEquals(2, BitmapUtil.getScaleFactor(2000, 1000, 500, 500, false));
+    assertEquals(2, BitmapUtil.getScaleFactor(1000, 2000, 499, 499, false));
+  }
+
+  public void testScaleFactorConstrained() {
+    assertEquals(1, BitmapUtil.getScaleFactor(1000, 1000, 9000, 9000, true));
+
+    assertEquals(2, BitmapUtil.getScaleFactor(1000, 1000, 750, 750, true));
+    assertEquals(2, BitmapUtil.getScaleFactor(1000, 1000, 500, 500, true));
+    assertEquals(4, BitmapUtil.getScaleFactor(1000, 1000, 499, 499, true));
+    assertEquals(4, BitmapUtil.getScaleFactor(1000, 1000, 250, 250, true));
+    assertEquals(8, BitmapUtil.getScaleFactor(1000, 1000, 249, 249, true));
+
+    assertEquals(2, BitmapUtil.getScaleFactor(1000, 500, 750, 750, true));
+    assertEquals(4, BitmapUtil.getScaleFactor(2000, 1000, 500, 500, true));
+    assertEquals(8, BitmapUtil.getScaleFactor(1000, 2000, 499, 499, true));
+  }
+}