android开发笔记之多媒体—图像的操作

不念不忘少年蓝@ 2022-07-24 05:23 168阅读 0赞

1.拿到原图

baseBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.img_small_1);

2.先拿到一张与原图一样大小的纸,内容空白

copyBitmap = Bitmap.createBitmap(baseBitmap.getWidth(), baseBitmap.getHeight(), baseBitmap.getConfig());

3.将这张纸固定在画板上

canvas = new Canvas(copyBitmap);

4.找一根画笔

paint = new Paint();

5.按照一定规则处理图片

Matrix matrix = new Matrix();//1:1

6.将处理过的图片画出来，照着原图画

canvas.drawBitmap(baseBitmap, matrix, paint);

7.将画好的图片的显示在ImageView组件上

iv.setImageBitmap(copyBitmap);

核心代码：

public class MainActivity extends Activity { 
    
        private ImageView iv;
        //画纸
        private Bitmap baseBitmap;  //原图
        private Bitmap copyBitmap;  
        //画布
        private Canvas canvas;
        //画笔
        private Paint paint;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            iv = (ImageView) findViewById(R.id.iv);
        }
        //处理图像
        public void operation(View view) {
            //1拿到原图
            baseBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.img_small_1);
            //2.先拿到一张与原图一样大小的纸,内容空白
            copyBitmap = Bitmap.createBitmap(baseBitmap.getWidth(), baseBitmap.getHeight(), baseBitmap.getConfig());
            //3.将这张纸固定在画板上
            canvas = new Canvas(copyBitmap);
            //4.找一根画笔
            paint = new Paint();
            paint.setAlpha(200);
            //5.按照一定规则处理图片
            Matrix matrix = new Matrix();//1:1
            //缩放
    // matrix.setScale(0.5f, 0.5f); //1:2即1/2
            //位移
    // matrix.setTranslate(50f, 50f);
            //旋转
    // matrix.setRotate(45f); //顺时针45度旋转，默认以图片左上角为原点
    // matrix.setRotate(45, baseBitmap.getWidth()/2, baseBitmap.getHeight()/2); //顺时针45度旋转，沿中心点旋转
            //镜面 
    // matrix.setScale(-1f, 1f);//翻面
    // matrix.postTranslate(baseBitmap.getWidth(), 0); //如果要对图片进行多次操作，则用postxxx();
            //倒影
            matrix.setScale(1f, -1f);
            matrix.postTranslate(0, baseBitmap.getHeight());
            //6.将处理过的图片画出来，照着原图画
            canvas.drawBitmap(baseBitmap, matrix, paint);
            iv.setImageBitmap(copyBitmap);
        }
    }

结果：

![这里写图片描述][20160514171238991]

[20160514171238991]: /images/20220722/b0eda4f65e7e4e9eb72d5023e3fba679.png