package com.kale.bitmaptest;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
public class BitUtils {
    private static int mDesiredWidth;
    private static int mDesiredHeight;
    /**
     * @description 从Resources中加载图片
     *
     * @param res
     * @param resId
     * @param reqWidth
     * @param reqHeight
     * @return
     */
    public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        // 设置成了true,不占用内存，只获取bitmap宽高
        options.inJustDecodeBounds = true; 
        // 初始化options对象
        BitmapFactory.decodeResource(res, resId, options); 
        // 得到计算好的options，目标宽、目标高
        options = getBestOptions(options, reqWidth, reqHeight);
        Bitmap src = BitmapFactory.decodeResource(res, resId, options); // 载入一个稍大的缩略图
        return createScaleBitmap(src, mDesiredWidth, mDesiredHeight); // 进一步得到目标大小的缩略图
    }
    /**
     * @description 从SD卡上加载图片
     *
     * @param pathName
     * @param reqWidth
     * @param reqHeight
     * @return
     */
    public static Bitmap decodeSampledBitmapFromFile(String pathName, int reqWidth, int reqHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(pathName, options);
        options = getBestOptions(options, reqWidth, reqHeight);
        Bitmap src = BitmapFactory.decodeFile(pathName, options);
        return createScaleBitmap(src, mDesiredWidth, mDesiredHeight);
    }
    /**
     * @description 计算目标宽度，目标高度，inSampleSize
     *
     * @param options
     * @param reqWidth
     * @param reqHeight
     * @return BitmapFactory.Options对象
     */
    private static BitmapFactory.Options getBestOptions(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // 读取图片长宽
        int actualWidth = options.outWidth;
        int actualHeight = options.outHeight;
        // Then compute the dimensions we would ideally like to decode to.
        mDesiredWidth = getResizedDimension(reqWidth, reqHeight, actualWidth, actualHeight);
        mDesiredHeight = getResizedDimension(reqHeight, reqWidth, actualHeight, actualWidth);
        // 根据现在得到计算inSampleSize
        options.inSampleSize = calculateBestInSampleSize(actualWidth, actualHeight, mDesiredWidth, mDesiredHeight);
        // 使用获取到的inSampleSize值再次解析图片
        options.inJustDecodeBounds = false;
        return options;
    }
    /**
     * Scales one side of a rectangle to fit aspect ratio. 最终得到重新测量的尺寸
     *
     * @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) {
        double ratio = (double) actualSecondary / (double) actualPrimary;
        int resized = maxPrimary;
        if (resized * ratio > maxSecondary) {
            resized = (int) (maxSecondary / ratio);
        }
        return resized;
    }
    /**
     * 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.
    private static int calculateBestInSampleSize(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 inSampleSize = 1.0f;
        while ((inSampleSize * 2) <= ratio) {
            inSampleSize *= 2;
        }
        return (int) inSampleSize;
    }
    /**
     * @description 通过传入的bitmap，进行压缩，得到符合标准的bitmap
     *
     * @param src
     * @param dstWidth
     * @param dstHeight
     * @return
     */
    private static Bitmap createScaleBitmap(Bitmap tempBitmap, int desiredWidth, int desiredHeight) {
        // If necessary, scale down to the maximal acceptable size.
        if (tempBitmap != null && (tempBitmap.getWidth() > desiredWidth || tempBitmap.getHeight() > desiredHeight)) {
            // 如果是放大图片，filter决定是否平滑，如果是缩小图片，filter无影响
            Bitmap bitmap = Bitmap.createScaledBitmap(tempBitmap, desiredWidth, desiredHeight, true);
            tempBitmap.recycle(); // 释放Bitmap的native像素数组
            return bitmap;
        } else {
            return tempBitmap; // 如果没有缩放，那么不回收
        }
    }
}

public void loadBitmap(boolean exactable) {
        int bmSize = 0;
        Bitmap bm = null;
        if (exactable) {
            // 通过工具类来产生一个符合ImageView的缩略图
            bm = BitUtils.decodeSampledBitmapFromResource(getResources(), R.drawable.saber, iv.getWidth(), iv.getHeight());
        } else {
            // 直接加载原图
            bm = BitmapFactory.decodeResource(getResources(), R.drawable.saber);
        }
        iv.setImageBitmap(bm);
        bmSize += bm.getByteCount(); // 得到bitmap的大小
        int kb = bmSize / 1024;
        int mb = kb / 1024;
        kb = kb % 1024;
        Log.d("Bitmap", "bitmap w = " + bm.getWidth() + " h = " + bm.getHeight());
        Log.d("Bitmap", "bitmap size = " + mb + "MB " + kb + "KB");
        Toast.makeText(this, "bitmap size = " + mb + "MB " + kb + "KB", Toast.LENGTH_LONG).show();
    }

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