Android Open Source - wristband-android Image Request

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License

The source code is released under:
The Artistic License 2.0 Copyright (c) 2014 Allan Pichardo Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed...
If you think the Android project wristband-android listed in this page is inappropriate, such as containing malicious code/tools or violating the copyright, please email info at java2s dot com, thanks.
Java Source Code

/*
 * Copyright (C) 2011 The Android Open Source Project
 */*w  w  w .j av  a  2s  . c o  m*/
 * 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.volley.toolbox;

import com.android.volley.DefaultRetryPolicy;
import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyLog;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;

/**
 * A canned request for getting an image at a given URL and calling
 * back with a decoded Bitmap.
 */
public class ImageRequest extends Request<Bitmap> {
    /** Socket timeout in milliseconds for image requests */
    private static final int IMAGE_TIMEOUT_MS = 1000;

    /** Default number of retries for image requests */
    private static final int IMAGE_MAX_RETRIES = 2;

    /** Default backoff multiplier for image requests */
    private static final float IMAGE_BACKOFF_MULT = 2f;

    private final Response.Listener<Bitmap> mListener;
    private final Config mDecodeConfig;
    private final int mMaxWidth;
    private final int mMaxHeight;

    /** Decoding lock so that we don't decode more than one image at a time (to avoid OOM's) */
    private static final Object sDecodeLock = new Object();

    /**
     * Creates a new image request, decoding to a maximum specified width and
     * height. If both width and height are zero, the image will be decoded to
     * its natural size. If one of the two is nonzero, that dimension will be
     * clamped and the other one will be set to preserve the image's aspect
     * ratio. If both width and height are nonzero, the image will be decoded to
     * be fit in the rectangle of dimensions width x height while keeping its
     * aspect ratio.
     *
     * @param url URL of the image
     * @param listener Listener to receive the decoded bitmap
     * @param maxWidth Maximum width to decode this bitmap to, or zero for none
     * @param maxHeight Maximum height to decode this bitmap to, or zero for
     *            none
     * @param decodeConfig Format to decode the bitmap to
     * @param errorListener Error listener, or null to ignore errors
     */
    public ImageRequest(String url, Response.Listener<Bitmap> listener, int maxWidth, int maxHeight,
            Config decodeConfig, Response.ErrorListener errorListener) {
        super(Method.GET, url, errorListener);
        setRetryPolicy(
                new DefaultRetryPolicy(IMAGE_TIMEOUT_MS, IMAGE_MAX_RETRIES, IMAGE_BACKOFF_MULT));
        mListener = listener;
        mDecodeConfig = decodeConfig;
        mMaxWidth = maxWidth;
        mMaxHeight = maxHeight;
    }

    @Override
    public Priority getPriority() {
        return Priority.LOW;
    }

    /**
     * Scales one side of a rectangle to fit aspect ratio.
     *
     * @param maxPrimary Maximum size of the primary dimension (i.e. width for
     *        max width), or zero to maintain aspect ratio with secondary
     *        dimension
     * @param maxSecondary Maximum size of the secondary dimension, or zero to
     *        maintain aspect ratio with primary dimension
     * @param actualPrimary Actual size of the primary dimension
     * @param actualSecondary Actual size of the secondary dimension
     */
    private static int getResizedDimension(int maxPrimary, int maxSecondary, int actualPrimary,
            int actualSecondary) {
        // If no dominant value at all, just return the actual.
        if (maxPrimary == 0 && maxSecondary == 0) {
            return actualPrimary;
        }

        // If primary is unspecified, scale primary to match secondary's scaling ratio.
        if (maxPrimary == 0) {
            double ratio = (double) maxSecondary / (double) actualSecondary;
            return (int) (actualPrimary * ratio);
        }

        if (maxSecondary == 0) {
            return maxPrimary;
        }

        double ratio = (double) actualSecondary / (double) actualPrimary;
        int resized = maxPrimary;
        if (resized * ratio > maxSecondary) {
            resized = (int) (maxSecondary / ratio);
        }
        return resized;
    }

    @Override
    protected Response<Bitmap> parseNetworkResponse(NetworkResponse response) {
        // Serialize all decode on a global lock to reduce concurrent heap usage.
        synchronized (sDecodeLock) {
            try {
                return doParse(response);
            } catch (OutOfMemoryError e) {
                VolleyLog.e("Caught OOM for %d byte image, url=%s", response.data.length, getUrl());
                return Response.error(new ParseError(e));
            }
        }
    }

    /**
     * The real guts of parseNetworkResponse. Broken out for readability.
     */
    private Response<Bitmap> doParse(NetworkResponse response) {
        byte[] data = response.data;
        BitmapFactory.Options decodeOptions = new BitmapFactory.Options();
        Bitmap bitmap = null;
        if (mMaxWidth == 0 && mMaxHeight == 0) {
            decodeOptions.inPreferredConfig = mDecodeConfig;
            bitmap = BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
        } else {
            // If we have to resize this image, first get the natural bounds.
            decodeOptions.inJustDecodeBounds = true;
            BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
            int actualWidth = decodeOptions.outWidth;
            int actualHeight = decodeOptions.outHeight;

            // Then compute the dimensions we would ideally like to decode to.
            int desiredWidth = getResizedDimension(mMaxWidth, mMaxHeight,
                    actualWidth, actualHeight);
            int desiredHeight = getResizedDimension(mMaxHeight, mMaxWidth,
                    actualHeight, actualWidth);

            // Decode to the nearest power of two scaling factor.
            decodeOptions.inJustDecodeBounds = false;
            // TODO(ficus): Do we need this or is it okay since API 8 doesn't support it?
            // decodeOptions.inPreferQualityOverSpeed = PREFER_QUALITY_OVER_SPEED;
            decodeOptions.inSampleSize =
                findBestSampleSize(actualWidth, actualHeight, desiredWidth, desiredHeight);
            Bitmap tempBitmap =
                BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);

            // If necessary, scale down to the maximal acceptable size.
            if (tempBitmap != null && (tempBitmap.getWidth() > desiredWidth ||
                    tempBitmap.getHeight() > desiredHeight)) {
                bitmap = Bitmap.createScaledBitmap(tempBitmap,
                        desiredWidth, desiredHeight, true);
                tempBitmap.recycle();
            } else {
                bitmap = tempBitmap;
            }
        }

        if (bitmap == null) {
            return Response.error(new ParseError(response));
        } else {
            return Response.success(bitmap, HttpHeaderParser.parseCacheHeaders(response));
        }
    }

    @Override
    protected void deliverResponse(Bitmap response) {
        mListener.onResponse(response);
    }

    /**
     * Returns the largest power-of-two divisor for use in downscaling a bitmap
     * that will not result in the scaling past the desired dimensions.
     *
     * @param actualWidth Actual width of the bitmap
     * @param actualHeight Actual height of the bitmap
     * @param desiredWidth Desired width of the bitmap
     * @param desiredHeight Desired height of the bitmap
     */
    // Visible for testing.
    static int findBestSampleSize(
            int actualWidth, int actualHeight, int desiredWidth, int desiredHeight) {
        double wr = (double) actualWidth / desiredWidth;
        double hr = (double) actualHeight / desiredHeight;
        double ratio = Math.min(wr, hr);
        float n = 1.0f;
        while ((n * 2) <= ratio) {
            n *= 2;
        }

        return (int) n;
    }
}
Java Source Code List
