Android Bitmap Thumbnail Create extractThumbnail(Bitmap source, int width, int height, int options)

Description

Creates a centered bitmap of the desired size.

Parameter

Parameter	Description
source	original bitmap source
width	targeted width
height	targeted height
options	options used during thumbnail extraction

Declaration

public static Bitmap extractThumbnail(Bitmap source, int width,
        int height, int options) 

Method Source Code

//package com.java2s;

import android.graphics.Bitmap;

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

public class Main {
    private static final int OPTIONS_NONE = 0x0;
    private static final int OPTIONS_SCALE_UP = 0x1;
    /**//from   w  ww  .  jav a 2  s. c  o  m
     * 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;
    }
}

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