Implement the new Photo picker, part two.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/BitmapUtils.java

+// Copyright 2017 The Chromium Authors. All rights reserved.

[Theresa, 2017/03/31 18:05:55]

Is this class being used anywhere currently?

[Finnur, 2017/04/03 17:30:29]

Huh... You are right. Removed.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.photo_picker;
+
+import android.graphics.Bitmap;
+import android.graphics.BitmapFactory;
+
+import java.io.FileDescriptor;
+
+class BitmapUtils {
+    /**
+     * Takes a |bitmap| and returns a square thumbnail of |width| from the center of the bitmap
+     * specified.
+     * @param bitmap The bitmap to adjust.
+     * @param width The desired width.
+     * @return The new bitmap thumbnail.
+     */
+    public static Bitmap sizeBitmap(Bitmap bitmap, int width) {
+        bitmap = ensureMinSize(bitmap, width);
+        bitmap = cropToSquare(bitmap, width);
+        return bitmap;
+    }
+
+    /**
+     * Given a FileDescriptor, decodes the contents and returns a bitmap of size |width|x|width|.
+     * @param descriptor The FileDescriptor for the file to read.
+     * @param width The width of the bitmap to return.
+     * @return The resulting bitmap.
+     */
+    public static Bitmap decodeBitmapFromFileDescriptor(FileDescriptor descriptor, int width) {
+        BitmapFactory.Options options = createSizingOptions();
+        BitmapFactory.decodeFileDescriptor(descriptor, null, options);
+        Bitmap bitmap = BitmapFactory.decodeFileDescriptor(

[Theresa, 2017/03/31 18:05:55]

Why does this call decodeFileDescriptor twice? Same question for the double call
to decodeFile in #decodeBitmapFromDisk below.

[Finnur, 2017/04/03 17:30:29]

Because that's how the sub-sampling is implemented in Android. You call decode
twice, first with inJustDecodeBounds=true (which tells you the dimensions of the
image on disk) and then you can use those dimensions to set inSampleSize to
decode the image to the desired thumbnail size.

However, I've come to realize that I no longer need decodeBitmapFromDisk, which
was the impetus for creating two utility functions below it, so I've deleted it
and transformed the remaining three into one again. But that's for a later
review, since this file isn't needed yet.

+                descriptor, null, createDecodingOptions(options, width));
+
+        if (bitmap == null) return null;
+
+        return sizeBitmap(bitmap, width);
+    }
+
+    /**
+     * Given a file path, decodes the contents of the file and returns a bitmap of size
+     * |width|x|width|.
+     * @param filePath The path to the file to read.
+     * @param width The width of the bitmap to return.
+     * @return The resulting bitmap.
+     */
+    public static Bitmap decodeBitmapFromDisk(String filePath, int width) {
+        BitmapFactory.Options options = createSizingOptions();
+        BitmapFactory.decodeFile(filePath, options);
+        Bitmap bitmap = BitmapFactory.decodeFile(filePath, createDecodingOptions(options, width));
+
+        if (bitmap == null) return null;
+
+        return sizeBitmap(bitmap, width);
+    }
+
+    /**
+     * Creates a {@link BitmapFactory#Options} object ready for size calculations.
+     */
+    private static BitmapFactory.Options createSizingOptions() {
+        BitmapFactory.Options options = new BitmapFactory.Options();
+        options.inJustDecodeBounds = true;
+        return options;
+    }
+
+    /**
+     * Converts a {@link BitmapFactory#Options} object for size calculations into a decoding options
+     * object, with optimal decoding size specified.
+     */
+    private static BitmapFactory.Options createDecodingOptions(
+            BitmapFactory.Options sizingOptions, int width) {
+        sizingOptions.inSampleSize = calculateInSampleSize(sizingOptions, width, width);
+        sizingOptions.inJustDecodeBounds = false;
+        return sizingOptions;
+    }
+
+    /**
+     * Calculates the sub-sampling factor {@link BitmapFactory#inSampleSize} option for a given
+     * bitmap option, which will be used to create a bitmap of a pre-determined size (no larger than
+     * |width| and |height|).
+     * @param options The bitmap options to consider.
+     * @param width The requested width.
+     * @param height The requested height.
+     * @return The sub-sampling factor (1 = no change, 2 = half-size, etc).
+     */
+    private static int calculateInSampleSize(BitmapFactory.Options options, int width, int height) {
+        int inSampleSize = 1;
+
+        if (options.outHeight > height || options.outWidth > width) {
+            final int halfHeight = options.outHeight / 2;
+            final int halfWidth = options.outWidth / 2;
+
+            while ((halfHeight / inSampleSize) >= height || (halfWidth / inSampleSize) >= width) {
+                inSampleSize *= 2;
+            }
+        }
+
+        return inSampleSize;
+    }
+
+    /**
+     * Scales a |bitmap| to a certain size.
+     * @param bitmap The bitmap to scale.
+     * @param scaleMaxSize What to scale it to.
+     * @param filter True if the source should be filtered.
+     * @return The resulting scaled bitmap.
+     */
+    public static Bitmap scale(Bitmap bitmap, float scaleMaxSize, boolean filter) {
+        float ratio = Math.min((float) scaleMaxSize / bitmap.getWidth(),
+                (float) scaleMaxSize / bitmap.getHeight());
+        int height = Math.round(ratio * bitmap.getHeight());
+        int width = Math.round(ratio * bitmap.getWidth());
+
+        return Bitmap.createScaledBitmap(bitmap, width, height, filter);
+    }
+
+    /**
+     * Ensures a |bitmap| is at least |size| in both width and height.
+     * @param bitmap The bitmap to modify.
+     * @param size The minimum size (width and height).
+     * @return The resulting (scaled) bitmap.
+     */
+    private static Bitmap ensureMinSize(Bitmap bitmap, int size) {
+        int width = bitmap.getWidth();
+        int height = bitmap.getHeight();
+        if (width < size) {
+            float scale = (float) size / width;
+            width = size;
+            height *= scale;
+        }
+
+        if (height < size) {
+            float scale = (float) size / height;
+            height = size;
+            width *= scale;
+        }
+
+        return Bitmap.createScaledBitmap(bitmap, width, height, true);
+    }
+
+    /**
+     * Crops a |bitmap| to a certain square |size|
+     * @param bitmap The bitmap to crop.
+     * @param size The size desired (width and height).
+     * @return The resulting (square) bitmap.
+     */
+    private static Bitmap cropToSquare(Bitmap bitmap, int size) {
+        int x = 0;
+        int y = 0;
+        int width = bitmap.getWidth();
+        int height = bitmap.getHeight();
+
+        if (width > size) x = (width - size) / 2;
+        if (height > size) y = (height - size) / 2;
+        return Bitmap.createBitmap(bitmap, x, y, size, size);
+    }
+}