[douban] 02_图片处理1-图片比例缩放（opts.inJustDecodeBounds = true）

Android 4.0

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图片处理1-图片比例缩放

缩放时，按照大的缩放，才能保证图片在手机上完整的显示出来

// 1. 首先得到屏幕的宽高

WindowManager manager = getWindowManager();

Display display = manager.getDefaultDisplay();

int screenWidth = display.getWidth();

int screenHeight = display.getHeight();

System.out.println("屏幕宽度：" + screenWidth);

System.out.println("屏幕高度：" + screenHeight);

// 2. 获取图片的宽度和高度,不会真正的解析这个位图,只会获取这个位图在计算机存储的头信息

Options opts = new Options();

// 设置inJustDecodeBounds = true ;

opts.inJustDecodeBounds = true;

Bitmap bm = BitmapFactory.decodeResource(getResources(), IMGS[position%IMGS.length],opts);

// int imgWidth = bm.getWidth();

// int imgHeight = bm.getHeight();

// 获取图片宽高，不能用上面的，要用下面的,因为opts为true，此时bm为null

int imgWidth = opts.outWidth;

int imgHeight = opts.outHeight;

System.out.println("图片宽度：" + imgWidth);

System.out.println("图片高度：" + imgHeight);

int resizeX = imgWidth / screenWidth;

int resizeY = imgHeight / screenHeight;

int size = 0;

if (resizeX > resizeY) {

size = resizeX;

} else {

size = resizeY;

}

// 3、设置缩放比例

opts.inSampleSize = size;

System.out.println("缩放比例：" + size);

opts.inJustDecodeBounds = false;

// 4、真正的解析位图

bm = BitmapFactory.decodeResource(getResources(), IMGS[position%IMGS.length],opts);

完整代码：


                
                  package cn.zengfansheng.resize;
 
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.os.Bundle;
import android.view.Display;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
 
public class MainActivity extends Activity {
 
    private ListView lv;
 
    private final int[] IMGS = {
            R.drawable.imag_1, R.drawable.imag_2,
            R.drawable.imag_3, R.drawable.imag_4, R.drawable.imag_5,
    };
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
        setContentView(R.layout.activity_main);
        lv = (ListView) this.findViewById(R.id.lv_img);
        ListAdapter adapter = new MyAdapter();
        lv.setAdapter(adapter );
    }
 
    private class MyAdapter extends BaseAdapter{
 
        @Override
        public int getCount() {
            return IMGS.length * 2;
        }
 
        @Override
        public Object getItem(int position) {
            return IMGS[position];
        }
 
        @Override
        public long getItemId(int position) {
            return position;
        }
 
        @SuppressWarnings("deprecation")
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
 
            View view = null;
            TextView tvImg = null;
            ImageView ivImg = null;
            if (convertView != null && convertView instanceof TextView) {
                view = convertView;
            } else {
                view = View.inflate(getApplicationContext(), R.layout.lv_item, null);
 
                tvImg = (TextView) view.findViewById(R.id.tv_img);
                ivImg = (ImageView) view.findViewById(R.id.iv_img);
            }
            tvImg.setText("第" + (position + 1) + "张图片");
 
//            Bitmap bm = BitmapFactory.decodeResource(getResources(), IMGS[position%IMGS.length]);
 
            // 1. 首先得到屏幕的宽高
            WindowManager manager = getWindowManager();
            Display display = manager.getDefaultDisplay();
            int screenWidth = display.getWidth();
            int screenHeight = display.getHeight();
 
            System.out.println("屏幕宽度：" + screenWidth);
            System.out.println("屏幕高度：" + screenHeight);
 
            // 2. 获取图片的宽度和高度,不会真正的解析这个位图,只会获取这个位图在计算机存储的头信息
            Options opts = new Options();
            // 设置inJustDecodeBounds = true ;
            opts.inJustDecodeBounds = true;
            Bitmap bm = BitmapFactory.decodeResource(getResources(), IMGS[position%IMGS.length],opts);
 
            // int imgWidth = bm.getWidth();
            // int imgHeight = bm.getHeight();
            // 获取图片宽高，不能用上面的，要用下面的,因为opts为true，此时bm为null
            int imgWidth = opts.outWidth;
            int imgHeight = opts.outHeight;
 
            System.out.println("图片宽度：" + imgWidth);
            System.out.println("图片高度：" + imgHeight);
 
            int resizeX = imgWidth / screenWidth;
            int resizeY = imgHeight / screenHeight;
 
            int size = 0;
            if (resizeX > resizeY) {
                size = resizeX;
            } else {
                size = resizeY;
            }
            // 3、设置缩放比例
            opts.inSampleSize = size;
            System.out.println("缩放比例：" + size);
 
            opts.inJustDecodeBounds = false;
            // 4、真正的解析位图
            bm = BitmapFactory.decodeResource(getResources(), IMGS[position%IMGS.length],opts);
            ivImg.setImageBitmap(bm);
 
            return view;
        }
 
    }
 
}

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