android中的图片处理

package xidian.dy.com.chujia;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.Display;
import android.view.View;
import android.widget.ImageView;

import java.io.File;

public class MainActivity extends AppCompatActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    public void load(View v){
        BitmapFactory.Options options = new BitmapFactory.Options();
        File file = new File(Environment.getExternalStorageDirectory(), "a.dog");
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(file.toString(), options);
        //获取图片宽高
        int imgWidth = options.outWidth;
        int imgHeight = options.outHeight;
        //获取屏幕宽高
        Display dsp = getWindowManager().getDefaultDisplay();
        int screanWidth = dsp.getWidth();
        int screanHeight = dsp.getHeight();
        //计算缩放比例
        int scaleWidth = imgWidth / screanWidth;
        int scaleHeight = imgHeight / screanHeight;
        int scale = scaleHeight >= scaleWidth ? scaleHeight:scaleWidth;
        if(scale < 1)
            scale = 1;
        //设置缩放比例(scale应大于1缩放才能其作用)
        options.inSampleSize = scale;
        options.inJustDecodeBounds = false;
        Bitmap bm = BitmapFactory.decodeFile(file.toString(), options);

        ImageView img = (ImageView) findViewById(R.id.iv);
        if(img != null)
            img.setImageBitmap(bm);
    }
}

package xidian.dy.com.chujia;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Bitmap bm = BitmapFactory.decodeFile("/sdcard/a.dog");
        //创建一个与原图等宽高的bitmap对象,可以看作是画纸
        Bitmap bmcpy = Bitmap.createBitmap(bm.getWidth(), bm.getHeight(),bm.getConfig());

        //创建画笔对象
        Paint paint = new Paint();
        //创建画板对象,将画纸铺在画板上
        Canvas canvas = new Canvas(bmcpy);
        //开始作画
        //将图片水平翻转
        Matrix mt = new Matrix();
        mt.setScale(-1, 1);
        mt.postTranslate(bmcpy.getWidth(), 0);
        canvas.drawBitmap(bm, mt, paint);
        ImageView iv = (ImageView) findViewById(R.id.iv2);
        iv.setImageBitmap(bmcpy);
        ImageView iv1 = (ImageView) findViewById(R.id.iv1);
        iv1.setImageBitmap(bm);
    }
}