多媒体——图片——对图片进行简单加工

刺骨的言语ヽ痛彻心扉 2024-04-03 08:59 17阅读 0赞

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当图像视图的缩放类型为fitCenter时，如果图片的尺寸超过4096\*4096，App运行会崩溃。

若想解决加载超大图片的问题，有下列几种方案：

(1)在显示图片之前调用setLayerType方法，将图层类型设置为软件加速，此时系统会对该视图关闭硬件加速。

(2)把图像视图的缩放类型改为center，表示保持图片的原尺寸并居中显示。

(3)缩放类型保持fitCenter，同时事先缩小位图的尺寸，直至新位图的宽高均不超过4096。

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权限：

<uses-permission android:name="android.permission.CAMERA" />
        
        <uses-permission android:name="android.permission.RECORD_AUDIO" />
        
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />

布局：

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item\_select.xml

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代码：

package com.example.myapplication;
    
    import android.content.Intent;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.net.Uri;
    import android.os.Bundle;
    import androidx.appcompat.app.AppCompatActivity;
    import android.util.Log;
    import android.view.View;
    import android.widget.AdapterView;
    import android.widget.ArrayAdapter;
    import android.widget.ImageView;
    import android.widget.Spinner;
    import android.widget.AdapterView.OnItemSelectedListener;
    import com.example.myapplication.util.BitmapUtil;
    import java.io.InputStream;
    
    public class MainActivity extends AppCompatActivity implements View.OnClickListener
    {
    
        private final static String TAG = "ImageChangeActivity";
        private ImageView iv_photo; // 声明一个图像视图对象
        private Bitmap mBitmap; // 声明一个位图对象
        private Uri mImageUri; // 图片的路径对象
        private int CHOOSE_CODE = 3; // 选择照片的请求码
        private float mDegree; // 旋转角度
        private float mRatio; // 缩放比例
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
    
            iv_photo = findViewById(R.id.iv_photo);
            findViewById(R.id.btn_choose).setOnClickListener(this);
            initScaleSpinner(); // 初始化缩放比率下拉框
            initRotateSpinner(); // 初始化旋转角度下拉框
        }
    
        @Override
        public void onClick(View v) {
            if (v.getId() == R.id.btn_choose) {
                // 创建一个内容获取动作的意图(准备跳到系统相册)
                Intent albumIntent = new Intent(Intent.ACTION_GET_CONTENT);
                albumIntent.setType("image/*"); // 设置内容类型为图像
                startActivityForResult(albumIntent, CHOOSE_CODE); // 打开系统相册
            }
        }
    
        // 初始化缩放比率下拉框
        private void initScaleSpinner() {
            ArrayAdapter<String> scaleAdapter = new ArrayAdapter<String>(this,
                    R.layout.item_select, scaleArray);
            Spinner sp_scale = findViewById(R.id.sp_scale);
            sp_scale.setPrompt("请选择缩放比率");
            sp_scale.setAdapter(scaleAdapter);
            sp_scale.setOnItemSelectedListener(new ScaleSelectedListener());
            sp_scale.setSelection(0);
        }
    
        private String[] scaleArray = {"1.0", "0.5", "0.2", "0.10", "0.05", "0.01"};
        class ScaleSelectedListener implements OnItemSelectedListener {
            public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
                mRatio = Float.parseFloat(scaleArray[arg2]);
                showChangedImage(); // 显示变更后的图像
            }
    
            public void onNothingSelected(AdapterView<?> arg0) {}
        }
    
        // 初始化旋转角度下拉框
        private void initRotateSpinner() {
            ArrayAdapter<String> rotateAdapter = new ArrayAdapter<String>(this,
                    R.layout.item_select, rotateArray);
            Spinner sp_rotate = findViewById(R.id.sp_rotate);
            sp_rotate.setPrompt("请选择旋转角度");
            sp_rotate.setAdapter(rotateAdapter);
            sp_rotate.setOnItemSelectedListener(new RotateSelectedListener());
            sp_rotate.setSelection(0);
        }
    
        private String[] rotateArray = {"0", "45", "90", "135", "180", "225", "270", "315"};
        class RotateSelectedListener implements OnItemSelectedListener {
            public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
                mDegree = Integer.parseInt(rotateArray[arg2]);
                showChangedImage(); // 显示变更后的图像
            }
    
            public void onNothingSelected(AdapterView<?> arg0) {}
        }
    
        // 显示变更后的图像
        private void showChangedImage() {
            if (mBitmap != null) {
                // 获得缩放后的位图对象
                Bitmap bitmap = BitmapUtil.getScaleBitmap(mBitmap, mRatio);
                // 获得旋转后的位图对象
                bitmap = BitmapUtil.getRotateBitmap(bitmap, mDegree);
                iv_photo.setImageBitmap(bitmap); // 设置图像视图的位图对象
            }
        }
    
        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
            super.onActivityResult(requestCode, resultCode, intent);
            if (resultCode == RESULT_OK && requestCode == CHOOSE_CODE) {
                if (intent.getData() != null) { // 从相册选择一张照片
                    mImageUri = intent.getData();
                    // 打开指定uri获得输入流对象
                    try (InputStream is = getContentResolver().openInputStream(mImageUri)) {
                        // 从输入流解码得到原始的位图对象
                        mBitmap = BitmapFactory.decodeStream(is);
                        iv_photo.setImageBitmap(mBitmap); // 设置图像视图的位图对象
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    Log.d(TAG, "uri.getPath="+mImageUri.getPath()+",uri.toString="+mImageUri.toString());
                }
            }
        }
    
    }

BitmapUtil

package com.example.myapplication.util;
    
    import android.content.Context;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.graphics.Matrix;
    import android.net.Uri;
    import android.util.Log;
    import java.io.InputStream;
    
    public class BitmapUtil
    {
        private final static String TAG = "BitmapUtil";
    
        // 获得旋转角度之后的位图对象
        public static Bitmap getRotateBitmap(Bitmap bitmap, float rotateDegree)
        {
    
            Matrix matrix = new Matrix(); // 创建操作图片用的矩阵对象
            matrix.postRotate(rotateDegree); // 执行图片的旋转动作
    
            // 创建并返回旋转后的位图对象
            return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
        }
    
        // 获得比例缩放之后的位图对象
        public static Bitmap getScaleBitmap(Bitmap bitmap, double scaleRatio)
        {
    
            int new_width = (int) (bitmap.getWidth() * scaleRatio);
            int new_height = (int) (bitmap.getHeight() * scaleRatio);
    
            // 创建并返回缩放后的位图对象
            return Bitmap.createScaledBitmap(bitmap, new_width, new_height, false);
        }
    
        // 获得自动缩小后的位图对象
        public static Bitmap getAutoZoomImage(Context ctx, Uri uri)
        {
    
            Log.d(TAG, "getAutoZoomImage uri="+uri.toString());
            Bitmap zoomBitmap = null;
    
            // 打开指定uri获得输入流对象
            try (InputStream is = ctx.getContentResolver().openInputStream(uri))
            {
    
                // 从输入流解码得到原始的位图对象
                Bitmap originBitmap = BitmapFactory.decodeStream(is);
    
                int ratio = originBitmap.getWidth()/2000+1;
    
                // 获得比例缩放之后的位图对象
                zoomBitmap = BitmapUtil.getScaleBitmap(originBitmap, 1.0/ratio);
            }
            catch (Exception e)
            {
    
                e.printStackTrace();
            }
    
            return zoomBitmap;
        }
    
    }

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