ImageResizer.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.alexbbb.uploadservice;

import java.io.InputStream;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;


/**
 * A simple subclass of {@link ImageWorker} that resizes images from resources given a target width
 * and height. Useful for when the input images might be too large to simply load directly into
 * memory.
 */
public class ImageResizer {

    /**
     * Decode and sample down a bitmap from resources to the requested width and height.
     *
     * @param res The resources object containing the image data
     * @param resId The resource id of the image data
     * @param reqWidth The requested width of the resulting bitmap
     * @param reqHeight The requested height of the resulting bitmap
     * @return A bitmap sampled down from the original with the same aspect ratio and dimensions
     *         that are equal to or greater than the requested width and height
     */
    public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
            int reqWidth, int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(res, resId, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeResource(res, resId, options);
    }

    /**
     * Decode and sample down a bitmap from a file to the requested width and height.
     *
     * @param filename The full path of the file to decode
     * @param reqWidth The requested width of the resulting bitmap
     * @param reqHeight The requested height of the resulting bitmap
     * @return A bitmap sampled down from the original with the same aspect ratio and dimensions
     *         that are equal to or greater than the requested width and height
     */
    public static synchronized Bitmap decodeSampledBitmapFromFile(String filename,
            int reqWidth, int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(filename, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeFile(filename, options);
    }
    
    /**
     * Decode and sample down a bitmap from a file to the requested width and height.
    *
    * @param filename The full path of the file to decode
    * @param reqWidth The requested width of the resulting bitmap
    * @param reqHeight The requested height of the resulting bitmap
    * @return A bitmap sampled down from the original with the same aspect ratio and dimensions
    *         that are equal to or greater than the requested width and height
    */
   public static synchronized Bitmap decodeSampledBitmapFromStream(InputStream stream,
           int reqWidth, int reqHeight) {

       // First decode with inJustDecodeBounds=true to check dimensions
       final BitmapFactory.Options options = new BitmapFactory.Options();
       options.inJustDecodeBounds = true;
       BitmapFactory.decodeStream(stream, null, options);

       // Calculate inSampleSize
       options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

       // Decode bitmap with inSampleSize set
       options.inJustDecodeBounds = false;
       return BitmapFactory.decodeStream(stream, null, options);
   }

    /**
     * Calculate an inSampleSize for use in a {@link BitmapFactory.Options} object when decoding
     * bitmaps using the decode* methods from {@link BitmapFactory}. This implementation calculates
     * the closest inSampleSize that will result in the final decoded bitmap having a width and
     * height equal to or larger than the requested width and height. This implementation does not
     * ensure a power of 2 is returned for inSampleSize which can be faster when decoding but
     * results in a larger bitmap which isn't as useful for caching purposes.
     *
     * @param options An options object with out* params already populated (run through a decode*
     *            method with inJustDecodeBounds==true
     * @param reqWidth The requested width of the resulting bitmap
     * @param reqHeight The requested height of the resulting bitmap
     * @return The value to be used for inSampleSize
     */
    public static int calculateInSampleSize(BitmapFactory.Options options,
            int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            if (width > height) {
                inSampleSize = Math.round((float) height / (float) reqHeight);
            } else {
                inSampleSize = Math.round((float) width / (float) reqWidth);
            }

            // This offers some additional logic in case the image has a strange
            // aspect ratio. For example, a panorama may have a much larger
            // width than height. In these cases the total pixels might still
            // end up being too large to fit comfortably in memory, so we should
            // be more aggressive with sample down the image (=larger
            // inSampleSize).

            final float totalPixels = width * height;

            // Anything more than 2x the requested pixels we'll sample down
            // further.
            final float totalReqPixelsCap = reqWidth * reqHeight * 2;

            while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
                inSampleSize++;
            }
        }
        return inSampleSize;
    }
}