package com.longluo.ebookreader.util;

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


public class BitmapUtils {
    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);
    }

    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) {

            /**   final int halfHeight = height / 2;
             final int halfWidth = width / 2;

             // Calculate the largest inSampleSize value that is a power of 2 and keeps both
             // height and width larger than the requested height and width.
             while ((halfHeight / inSampleSize) > reqHeight
             && (halfWidth / inSampleSize) > reqWidth) {
             inSampleSize *= 2;
             } */
            final int heightRatio = Math.round((float) height / (float) reqHeight);
            final int widthRatio = Math.round((float) width / (float) reqWidth);
            // 选择宽和高中最小的比率作为inSampleSize的值，这样可以保证最终图片的宽和高
            // 一定都不会大于等于目标的宽和高。
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;

        }

        return inSampleSize;
    }
}
