Here you can find the source of decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight)
public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight)
//package com.java2s; import android.content.res.Resources; import android.graphics.Bitmap; import android.graphics.BitmapFactory; public class Main { public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) { final BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeResource(res, resId, options); options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);//w w w .ja va 2 s. co m options.inJustDecodeBounds = false; return BitmapFactory.decodeResource(res, resId, options); } public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) { final int height = options.outHeight; final int width = options.outWidth; int inSampleSize = 1; if ((reqWidth > 0 && reqHeight > 0) && (height > reqHeight || width > reqWidth)) { if (width > height) { inSampleSize = Math.round((float) height / (float) reqHeight); } else { inSampleSize = Math.round((float) width / (float) reqWidth); } } return 0 == inSampleSize ? 1 : inSampleSize; } }