src/com/android/contacts/util/BitmapUtil.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.contacts.util;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;

/**
 * Provides static functions to decode bitmaps at the optimal size
 */
public class BitmapUtil {
    private BitmapUtil() {}

    /**
     * Returns Width or Height of the picture, depending on which size is smaller. Doesn't actually
     * decode the picture, so it is pretty efficient to run.
     */
    public static int getSmallerExtentFromBytes(byte[] bytes) {
        final BitmapFactory.Options options = new BitmapFactory.Options();

        // don't actually decode the picture, just return its bounds
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeByteArray(bytes, 0, bytes.length, options);

        // test what the best sample size is
        return Math.min(options.outWidth, options.outHeight);
    }

    /**
     * Finds the optimal sampleSize for loading the picture
     * @param originalSmallerExtent Width or height of the picture, whichever is smaller
     * @param targetExtent Width or height of the target view, whichever is bigger.
     *
     * If either one of the parameters is 0 or smaller, no sampling is applied
     */
    public static int findOptimalSampleSize(int originalSmallerExtent, int targetExtent) {
        // If we don't know sizes, we can't do sampling.
        if (targetExtent < 1) return 1;
        if (originalSmallerExtent < 1) return 1;

        // Test what the best sample size is. To do that, we find the sample size that gives us
        // the best trade-off between resulting image size and memory requirement. We allow
        // the down-sampled image to be 20% smaller than the target size. That way we can get around
        // unfortunate cases where e.g. a 720 picture is requested for 362 and not down-sampled at
        // all. Why 20%? Why not. Prove me wrong.
        int extent = originalSmallerExtent;
        int sampleSize = 1;
        while ((extent >> 1) >= targetExtent * 0.8f) {
            sampleSize <<= 1;
            extent >>= 1;
        }

        return sampleSize;
    }

    /**
     * Decodes the bitmap with the given sample size
     */
    public static Bitmap decodeBitmapFromBytes(byte[] bytes, int sampleSize) {
        final BitmapFactory.Options options;
        if (sampleSize <= 1) {
            options = null;
        } else {
            options = new BitmapFactory.Options();
            options.inSampleSize = sampleSize;
        }
        return BitmapFactory.decodeByteArray(bytes, 0, bytes.length, options);
    }

    /**
     * Retrieves a copy of the specified drawable resource, rotated by a specified angle.
     *
     * @param resources The current resources.
     * @param resourceId The resource ID of the drawable to rotate.
     * @param angle The angle of rotation.
     * @return Rotated drawable.
     */
    public static Drawable getRotatedDrawable(
            android.content.res.Resources resources, int resourceId, float angle) {

        // Get the original drawable and make a copy which will be rotated.
        Bitmap original = BitmapFactory.decodeResource(resources, resourceId);
        Bitmap rotated = Bitmap.createBitmap(
                original.getWidth(), original.getHeight(), Bitmap.Config.ARGB_8888);

        // Perform the rotation.
        Canvas tempCanvas = new Canvas(rotated);
        tempCanvas.rotate(angle, original.getWidth()/2, original.getHeight()/2);
        tempCanvas.drawBitmap(original, 0, 0, null);

        return new BitmapDrawable(resources,rotated);
    }

    /**
     * Given an input bitmap, scales it to the given width/height and makes it round.
     *
     * @param input {@link Bitmap} to scale and crop
     * @param targetWidth desired output width
     * @param targetHeight desired output height
     * @return output bitmap scaled to the target width/height and cropped to an oval. The
     *         cropping algorithm will try to fit as much of the input into the output as possible,
     *         while preserving the target width/height ratio.
     */
    public static Bitmap getRoundedBitmap(Bitmap input, int targetWidth, int targetHeight) {
        if (input == null) {
            return null;
        }
        final Bitmap.Config inputConfig = input.getConfig();
        final Bitmap result = Bitmap.createBitmap(targetWidth, targetHeight,
                inputConfig != null ? inputConfig : Bitmap.Config.ARGB_8888);
        final Canvas canvas = new Canvas(result);
        final Paint paint = new Paint();
        canvas.drawARGB(0, 0, 0, 0);
        paint.setAntiAlias(true);
        final RectF dst = new RectF(0, 0, targetWidth, targetHeight);
        canvas.drawOval(dst, paint);

        // Specifies that only pixels present in the destination (i.e. the drawn oval) should
        // be overwritten with pixels from the input bitmap.
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));

        final int inputWidth = input.getWidth();
        final int inputHeight = input.getHeight();

        // Choose the largest scale factor that will fit inside the dimensions of the
        // input bitmap.
        final float scaleBy = Math.min((float) inputWidth / targetWidth,
            (float) inputHeight / targetHeight);

        final int xCropAmountHalved = (int) (scaleBy * targetWidth / 2);
        final int yCropAmountHalved = (int) (scaleBy * targetHeight / 2);

        final Rect src = new Rect(
                inputWidth / 2 - xCropAmountHalved,
                inputHeight / 2 - yCropAmountHalved,
                inputWidth / 2 + xCropAmountHalved,
                inputHeight / 2 + yCropAmountHalved);

        canvas.drawBitmap(input, src, dst, paint);
        return result;
    }
}