图片二次采集和压缩 ---》需要清单文件声明注册读写权限

MainActivity

package com.example.renzhili20181107;

import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.Interpolator;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.annotation.Nullable;
import android.support.v4.content.CursorLoader;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.File;

public class MainActivity extends AppCompatActivity {
    private EditText width,height,liang;
    private ImageView imageView;
    private Button query,but;
    private final int UPDETE=100;
    private Uri uri;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //获取资源id
        width=findViewById(R.id.width);
        height=findViewById(R.id.height);
        liang=findViewById(R.id.liang);
        imageView=findViewById(R.id.image);
        query=findViewById(R.id.query);
        but=findViewById(R.id.but);
        //点击选取图片
        query.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //打开相册
                Intent intent = new Intent(Intent.ACTION_PICK);
                intent.setType("image/*");
                startActivityForResult(intent,UPDETE);
            }
        });
        //生成图片
        but.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (uri!=null) {
                    String fromURI = getRealPathFromURI(uri);
                    Bitmap bitmap = Utils.RequeryImage(fromURI, Integer.parseInt(width.getText().toString().trim()), Integer.parseInt(height.getText().toString().trim()));
                    bitmap = Utils.compress(bitmap, Integer.parseInt(liang.getText().toString().trim()), new File(Environment.getExternalStorageDirectory(), "tmp.jpg"));
                    imageView.setImageBitmap(bitmap);
                }else{
                    Toast.makeText(MainActivity.this,"没有选取照片",Toast.LENGTH_LONG).show();
                }
            }
        });

    }
    private String getRealPathFromURI(Uri contentUri) { //传入图片uri地址
        String[] proj = { MediaStore.Images.Media.DATA };
        CursorLoader loader = new CursorLoader(this, contentUri, proj, null, null, null);
        Cursor cursor = loader.loadInBackground();
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        return cursor.getString(column_index);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        if (requestCode==UPDETE&&resultCode==RESULT_OK){
            uri = data.getData();
            return;
        }

        super.onActivityResult(requestCode, resultCode, data);
    }
}

、、工具类

package com.example.renzhili20181107;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

import java.io.File;
import java.io.FileOutputStream;

public class Utils {


//二次采集
    public  static Bitmap RequeryImage(String urlimage, int width, int height){
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds=true;
        BitmapFactory.decodeFile(urlimage,options);
        options.inSampleSize=Math.max(options.outWidth/width,options.outHeight/height);
        options.inJustDecodeBounds=false;
        Bitmap bitmap = BitmapFactory.decodeFile(urlimage, options);
        return bitmap ;
    }
    //图片压缩
    public  static Bitmap compress(Bitmap bitmap, int qual, File output){
        Bitmap result=bitmap;
        try {
            bitmap.compress(Bitmap.CompressFormat.JPEG, qual, new FileOutputStream(output));
            result = BitmapFactory.decodeFile(output.getAbsolutePath());

        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
}