ThumbnailUtils.java

/*
 * Copyright (C) 2009 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 org.kontalk.util;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Rect;

/**
 * Thumbnail generation routines for media provider.
 */

public class ThumbnailUtils {
    /* Options used internally. */
    private static final int OPTIONS_NONE = 0x0;
    private static final int OPTIONS_SCALE_UP = 0x1;

    /**
     * Constant used to indicate we should recycle the input in
     * {@link #extractThumbnail(Bitmap, int, int, int)} unless the output is the input.
     */
    public static final int OPTIONS_RECYCLE_INPUT = 0x2;

    /**
     * Creates a centered bitmap of the desired size.
     *
     * @param source original bitmap source
     * @param width targeted width
     * @param height targeted height
     */
    public static Bitmap extractThumbnail(
            Bitmap source, int width, int height) {
        return extractThumbnail(source, width, height, OPTIONS_NONE);
    }

    /**
     * Creates a centered bitmap of the desired size.
     *
     * @param source original bitmap source
     * @param width targeted width
     * @param height targeted height
     * @param options options used during thumbnail extraction
     */
    public static Bitmap extractThumbnail(
            Bitmap source, int width, int height, int options) {
        if (source == null) {
            return null;
        }

        float scale;
        if (source.getWidth() < source.getHeight()) {
            scale = width / (float) source.getWidth();
        } else {
            scale = height / (float) source.getHeight();
        }
        Matrix matrix = new Matrix();
        matrix.setScale(scale, scale);
        Bitmap thumbnail = transform(matrix, source, width, height,
                OPTIONS_SCALE_UP | options);
        return thumbnail;
    }

    /**
     * Transform source Bitmap to targeted width and height.
     */
    private static Bitmap transform(Matrix scaler,
            Bitmap source,
            int targetWidth,
            int targetHeight,
            int options) {
        boolean scaleUp = (options & OPTIONS_SCALE_UP) != 0;
        boolean recycle = (options & OPTIONS_RECYCLE_INPUT) != 0;

        int deltaX = source.getWidth() - targetWidth;
        int deltaY = source.getHeight() - targetHeight;
        if (!scaleUp && (deltaX < 0 || deltaY < 0)) {
            /*
            * In this case the bitmap is smaller, at least in one dimension,
            * than the target.  Transform it by placing as much of the image
            * as possible into the target and leaving the top/bottom or
            * left/right (or both) black.
            */
            Bitmap b2 = Bitmap.createBitmap(targetWidth, targetHeight,
            Bitmap.Config.ARGB_8888);
            Canvas c = new Canvas(b2);

            int deltaXHalf = Math.max(0, deltaX / 2);
            int deltaYHalf = Math.max(0, deltaY / 2);
            Rect src = new Rect(
            deltaXHalf,
            deltaYHalf,
            deltaXHalf + Math.min(targetWidth, source.getWidth()),
            deltaYHalf + Math.min(targetHeight, source.getHeight()));
            int dstX = (targetWidth  - src.width())  / 2;
            int dstY = (targetHeight - src.height()) / 2;
            Rect dst = new Rect(
                    dstX,
                    dstY,
                    targetWidth - dstX,
                    targetHeight - dstY);
            c.drawBitmap(source, src, dst, null);
            if (recycle) {
                source.recycle();
            }
            return b2;
        }
        float bitmapWidthF = source.getWidth();
        float bitmapHeightF = source.getHeight();

        float bitmapAspect = bitmapWidthF / bitmapHeightF;
        float viewAspect   = (float) targetWidth / targetHeight;

        if (bitmapAspect > viewAspect) {
            float scale = targetHeight / bitmapHeightF;
            if (scale < .9F || scale > 1F) {
                scaler.setScale(scale, scale);
            } else {
                scaler = null;
            }
        } else {
            float scale = targetWidth / bitmapWidthF;
            if (scale < .9F || scale > 1F) {
                scaler.setScale(scale, scale);
            } else {
                scaler = null;
            }
        }

        Bitmap b1;
        if (scaler != null) {
            // this is used for minithumb and crop, so we want to filter here.
            b1 = Bitmap.createBitmap(source, 0, 0,
            source.getWidth(), source.getHeight(), scaler, true);
        } else {
            b1 = source;
        }

        if (recycle && b1 != source) {
            source.recycle();
        }

        int dx1 = Math.max(0, b1.getWidth() - targetWidth);
        int dy1 = Math.max(0, b1.getHeight() - targetHeight);

        Bitmap b2 = Bitmap.createBitmap(
                b1,
                dx1 / 2,
                dy1 / 2,
                targetWidth,
                targetHeight);

        if (b2 != b1) {
            if (recycle || b1 != source) {
                b1.recycle();
            }
        }

        return b2;
    }

}